Journal of Experimental Botany, Vol. 54, No. 389, pp. 1801-1812,
August 1, 2003
© 2003 Oxford University Press
Flower opening and closure: a review
Received 12 November 2002; Accepted 8 May 2003
1 Agrotechnological Research Institute (ATO), Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, The Netherlands
2 Horticultural Production Chains Group, Wageningen University and Research Centre, Marijkeweg 22, 6709 PG Wageningen, The Netherlands
* To whom correspondence should be sent. Fax: +31 317 475347. E-mail: wouter.vandoorn{at}wur.nl
 |
Abstract |
|---|
 Top Abstract IntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
Flower opening and closure are traits of a reproductive syndrome, as it allows pollen removal and/or pollination. Various types of opening can be distinguished such as nocturnal and diurnal and single or repetitive. Opening is generally due to cell expansion. Osmotic solute levels increase by the conversion of polysaccharides (starch or fructan) to monosaccharides, and/or the uptake of sugars from the apoplast. Repeated opening and closure movements are often brought about by differential elongation. In tulip petals, for example, the upper and lower sides of the mesophyll exhibit a 10 °C difference in optimum temperature for elongation growth, resulting in opening in the morning and closure in the evening. Opening and closure in several other species is regulated by changes in light intensity and, in some species with nocturnal opening, by an increase in relative humidity. A minimum duration of darkness and light are usually required for opening and closure, respectively, in flowers that open during the day. Both phytochrome and a blue light receptor seem involved in light perception. In some species, opening and closure are regulated by an endogenous rhythm, which, in all cases investigated, can be reset by changes from dark to light and/or light to dark. So far, Arabidopsis mutants have not been used to investigate the timing of flower opening and closure. As its flowers open and close in a circadian fashion, several mutants that are involved in the circadian clock and its light input may help to provide an insight into this type of flower opening. The co-ordination of processes culminating in synchronized flower opening is, in many species, highly intricate. The complex control by endogenous and exogenous factors sets flower opening and closure apart from most other growth processes.
Key words: Carbohydrate metabolism, circadian rhythm, differential growth, elongation growth, endogenous rhythm, fructans, hormonal regulation, osmotic potential, water relations.
|
Introduction |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
The time of flower opening marks the onset of a period in which pollinators will be attracted, leading to pollen removal in male and bisexual flowers and to pollination, fertilization and seed set in female and bisexual flowers. In many species the flowers are open permanently, whereby the opening period is terminated by a closure movement, or is terminated by petal withering or abscission. In other species, periods of opening are alternated by periods of closure.
Flower opening is often rapid. In Oenothera biennis, for example, full opening takes less than 20 min (Sigmond, 1930b) and in Hedera helix it occurs in about 5 min (Sigmond, 1929b). Flower opening is therefore interesting from a physiological point of view as, in many species, it is accompanied by a high rate of cell expansion, rather impressive movements, and complex regulation by external and internal factors. Time lapse photography shows that petal unfolding, depending on the species, shows spectacular outward spiralling, popping open, and various local movements in the petals whose final position often differs considerably from their position in the bud. It may be noted, in this scientific context, that flower opening has inspired many artists and seems of special emotional value to people.
No comprehensive review has been published previously on floral opening and closure, as far as is known. Therefore, the most interesting and thorough publications, including those that date from rather long ago, have been selected for this review. There is no attempt to give an historical perspective, but an effort is made to assign a first observation to the right author.
This review examines the classifications of flower opening and closure, the underlying mechanical processes, the role of environmental cues such as humidity, light and temperature, and that of endogenous rhythms. Some attention is also given to hormonal regulation, carbohydrate requirements and water relations. The paper concludes by discussing hypotheses about the selective advantages of the various strategies of floral opening and closure.
Several interesting papers on flower opening and closure were written in French, and some of the finest publications have been published in German. These papers are described here in somewhat more detail than the reports written in English. As a number of the publications mentioned date from some time ago, the plant nomenclature may have changed in the meantime. The names as given in the original reports have been used here.
|
Varieties of flower opening and closure |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
The reproductive structures of the Angiosperms differ vastly and it is therefore not surprising that the mechanism of flower opening also varies considerably. Several categories may be distinguished on the basis of the mechanics of flower opening (Sigmond, 1929a, b, 1930a, b; Reid and Evans, 1986).
Firstly, depending on the species, opening may relate to the development of tissues adjacent to the flower, for example, opening may require growth of the pedicel, as in several species in the Iridaceae; or it may require forced separation or abscission of covering parts, such as bracts or sepals. In some flowers, for example in Oenothera spp., the sepals are connected by a zipper-like mechanism whereby cells at the sepal margins are tangled. Due to the force of the growing petals this entanglement is broken and the petals are suddenly released. In several other species the sepal margins are tightly held together by ridges, which also delay opening until the growing petals overcome their resistance. This also results in rapid opening (Sigmond 1929a, 1930a). At least three types of abscission of adjacent tissues can be distinguished. (1) The abscission zone is at the base of a bract or sepal. (2) The abscission of a cover, horizontally, along its entire circumference. The cover may be soft, sepal-like tissue, as in some species in the Papaveraceae, or more woody as in Eucalyptus. (3) Cell separation that results in a vertical slit of a sepalous covering structure, as in several Papaveraceae.
Secondly, opening depends on petal movements, of which at least four types can be distinguished. (1) Opening is due to reversible ion accumulation, and independent of elongation growth; (2) it depends on cellular death in a specific area of the petal; (3) it is due to loss of water during the day and refilling during the night; and (4) it depends on differential growth.
These four types of flower opening will be discussed further. The characteristics of opening that have been mentioned are not mutually exclusive. Abscission of covering parts, or pedicel growth, for example, often occurs in combination with differential petal growth.
Flower closure can be due to differential growth or to reversible turgor changes, but it may also occur because of turgor loss due to senescence. In the latter case, the closure will be permanent. The petals usually fall after senescence, but the time span between senescence and abscission varies considerably, depending on the species. In several species the flowers never close, as the petals abscise when the flower is still open.
|
Mechanism of opening and closure |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
in most of the species studied, petal movements are due to a difference in growth rate of the two sides. In species that open in the morning and mainly respond to temperature, for example, the inner surface of the petal rapidly grows in length when the temperature is raised, whereas the outer surface does not. Cooling results in a more rapid growth of the outer surface (crocus: Wiedersheim, 1904; tulip: Pfeffer, 1873; Bünning, 1929; Böhner, 1934). In tulip petals, the mesophyll cells are mainly responsible for growth; the epidermal cells only follow mesophyll expansion. The optimum temperature for growth of the outer mesophyll cells was about 10 °C lower than that of the cells at the inner side (Wood, 1953). Other examples of petal movements due to unequal growth on both sides of the petals are: Anemone sp., Calendula sp., Colchium autumnale, Doronicum sp., Gentiana sp., Helleborus niger (Kerner von Marilaun, 1891), and Taraxacum albidum (Tanaka et al., 1987).
In Ipomoea (syn. Pharbitis), flower opening and closure are due to movements of the midrib rather than the petal lamina. Differences in cell expansion on both sides drive the movements (Kaihara and Takimoto, 1981a). The difference in cell expansion was due, in part, to turgor loss in a group of inner epidermal cells of the midrib. For 2 d prior to anthesis, the ultrastructure of these cells underwent rapid changes that are indicative of cell death. Other cells of the rib did not show these changes (Phillips and Kende, 1980).
Silene saxifraga flowers close during the day and open during the night for about 5 d. The petals roll up during the day. The inrolling (closing) movement was due to net water loss. Outrolling (opening) was apparently due to refilling of the cells with water. The flowers remain open longer on dry days if the soil is wet, and do not close at all on wet days (Halket, 1931). Several other Silene species show the same mechanism (Kraus, 1879; Kerner von Marilaun, 1891; Lindman, 1897).
Opening and closure may be due to reversible expansion and contraction of cells. To date this has only been convincingly demonstrated in Gentiana kochiana. The petals in this species are about 5 cm long and are fused at the basal end. Petals contain a 1–2 cm long zone that expands and contracts at 1–3 cm beneath the petal tips. Detailed measurements on both sides of the petal showed that the epidermis cells on the inner side expanded during the day and contracted at night. The outer epidermis, by contrast, did not show a change in length. It was concluded that the movements are due to turgor changes (Claus, 1926). A similar mechanism has been suggested for Kalanchoë blossfeldiana. As in Gentiana, the lowermost halves of the petals are fused and show no movements, and the zone responsible for movement is located where the petals separate. Detailed measurements on cell length are lacking, but differences in petal fresh weight occurred in parallel with the movements (Becker, 1953; zur Lippe, 1957), which is an argument in favour of reversible movements. The osmolarity of the upper epidermis was twice as high during the day than during the night, which also suggests reversible ion uptake (Schrempf, 1977). Abscisic acid dampened the rhythm of opening and closure, and diminished the rhythmic change in osmotic potential of the cells involved (Schrempf, 1980). In younger Kalanchoë flowers (in which the petals were still growing), opening and closing movements were stronger than in older flowers, in which elongation growth was no longer detectable (Karvé et al., 1961). This suggests that differential growth may also be involved in the movements, at least in young flowers.
In the following four sections the physiology of the growth reactions will be reviewed briefly, and only insofar as the data are specific for flower opening.
Carbohydrate metabolism
In most species, the mobilization of storage carbohydrates and/or the import of sucrose accompanies flower opening. Young petal cells of many species contain considerable amounts of starch which, shortly before opening, is rapidly converted to glucose and fructose (Ho and Nichols, 1977; Hammond, 1982). Young petals that reportedly contain high starch concentrations include Alstroemeria peregrina (Collier, 1997), Lilium (Bieleski et al., 2000b), Magnolia grandiflora (Griesel, 1954), Rosa (Ho and Nichols, 1977), Tradescantia reflexa (Horie, 1961), and Turnera ulmifolia (Ball, 1933). The important role of starch breakdown in lily petal growth was borne out by the use of degradation inhibitors (Bieleski et al., 2000b).
Petals of unopened daylily (Hemerocallis sp.) flowers, in contrast, contained no starch but a high concentration of fructan, an oligosaccharide with a high number of fructose monomers. Upon flower opening, fructan was rapidly degraded (Bieleski, 1993). Fructan also accumulated in the petals of Phipssia algida (Solhaug and Aares, 1994) and Campanula rapunculoides (Vergauwen et al., 2000), prior to opening.
Some petals contain both starch and fructan. In chrysanthemum petals, for example, both polysaccharides were degraded during petal expansion (Trusty and Miller, 1991). Finally, some flowers reportedly contain neither fructan nor starch (or only very low starch concentrations) just prior to opening. An example is Sandersonia (Eason et al., 1997; J Eason, personal communication, 2002). The petals of these species, nonetheless, do show increased contents of glucose and fructose, apparently as a result of sucrose uptake from the apoplast.
Flower opening may be due to a combination of sugar uptake and degradation of various polysaccharides. In gladiolus florets, where starch was a source of soluble carbohydrate, the increase in sugar content was 7–8 times higher than the decrease in starch content, which is indicative of sugar uptake (Yamane et al., 1991). Similarly, in freesia florets the increase in perianth sugars was more than 10 times higher than the decrease in starch content (van Meeteren et al., 1995). The sugar content and dry weight of opening freesia florets was dramatically reduced when stems were reduced in length, indicating that the stem was a major source of carbohydrate.
Competition for carbohydrates has been reported between petals of one flower, and among the opening flowers and flower buds. In cut Madelon roses, removal of the outer petals directly after harvest resulted in an increase in the surface area and in the sugar content of the innermost petals once they had fully developed (Marissen, 1991). Competition between buds follows from standard horticultural practice, where flower buds are removed in order to produce larger sized single flowers. Competition may be aggravated under conditions of restrained carbohydrate availability. In lily plants grown at low light intensity, for example, removal of young florets resulted in the increased dry weight of the remaining florets (van Meeteren et al., 2001).
Growing buds and opening flowers can hasten the time to senescence in flowers that are already open. Removal of floral buds in cut lily inflorescences clearly increased the longevity of the open flowers that remained attached (van der Meulen-Muisers et al., 1995). The life span of open lily flowers was also longer when they were detached, shortly after opening, from the inflorescence. A sharp decrease occurred in total carbohydrate content (starch, glucose, fructose, sucrose, and glycerol glucoside) in the petals of lily flowers that remained attached to the inflorescence, but a much smaller decrease was observed in detached flowers (van der Meulen-Muisers, 2000). These data indicate carbon transfer from senescing flowers to opening ones, at least in cut inflorescences held at low light intensities, in which sugars rapidly become limiting for bud growth and flower opening.
Cell wall expansion
Cell wall changes during flower growth and opening have thus far received little attention (Winkenbach, 1971; Wiemken-Gehrig et al., 1974; de Vetten and Huber, 1990; O’Donoghue et al., 2002a, b). Growing carnation petals showed high activities of cellulase and pectin esterase (Panavas et al., 1998). Brummel et al. (1999) demonstrated the expression of expansins, which are important in acid-induced cell wall loosening, in tomato flowers. However, acid-induced growth did not seem to control corolla expansion in Ipomoea nil. Applied fusicoccin (a proton efflux promoter) and sodium orthovanadate (an inhibitor) had no significant effect on the growth of young corollas. Buffers over a wide pH range also had no effect on the expansion (Raab and Koning, 1987).
Water relations
Cell elongation is usually very sensitive to a drop in water potential. Indeed, flower opening in cut rose flowers is often inhibited as a result of a blockage in the basal stem part, which results in a low water potential in the flower (van Doorn, 1997a). However, in some flowers, the leaves may be completely wilted but their flowers open normally. In cotton, for example, flower petals continued to expand when all leaves on the plant had wilted and the expansion of young leaves had ceased. The petals apparently removed water from other plant parts (Trolinder et al., 1993). Similarly, in cut chrysanthemum flowers, the leaves often wilt, due to a blockage for water transport in the xylem of the basal stem part. Nonetheless, the flowers remain turgid for a much longer period. The relative independence on water availability may be an adaptation to an environment where regular drought occurs. Once the flowers are formed in these species, reproduction apparently gets priority over the maintenance of vegetative tissue.
Hormonal regulation
Regulation by endogenous hormones, except for the role of ethylene, is as yet unclear. Gibberellin application promoted opening in several flowers, including Ipomoea nil (Raab and Koning, 1987), Gaillardia grandiflora (Koning, 1984) and statice (Steinitz and Cohen, 1982). Growth of isolated petals of Madelon roses, placed in water, depended on the position of the petal on the flower, as shown by Kuiper et al. (1991). About 15 of the outermost petals, if placed in water, reached the same area and fresh weight irrespective of sugar feeding. Area and FW were the same as in petals that remained attached to the intact plant. The second group reached full size only if sucrose was added to the water, and the third group (the innermost whorls) only fully expanded when placed in a solution containing GA3 and sucrose. The petals seem, therefore, to be dependent first on gibberellin and external carbohydrates, and then gradually to lose this dependence, starting with the hormone requirement. However, rigorous tests in which gibberellin synthesis or action was blocked have apparently not been reported.
Ethylene promoted or inhibited flower opening depending on the species. In roses, these differences even depended on the cultivar (Reid et al., 1989). A role of endogenous ethylene in opening followed from inhibitor studies in potted rose plants (Cushman et al., 1994; Tjosvold et al., 1995), cut rose flowers (Yamamoto et al., 1994) and cut gladiolus inflorescences (Serek et al., 1994).
Opening in Ipomoea nil flowers was promoted by ABA. Koning (1986) concluded that the effect of ABA in Ipomoea nil was due to increased ethylene production. The effect of ABA could be eliminated by the ethylene biosynthesis inhibitors aminoethoxyvinyl glycine and cobalt ions. Ipomoea flower opening was inhibited by IAA (Kaihara and Takimoto, 1983). As IAA can promote or inhibit ethylene production, depending on the concentration and the tissue, the effects of IAA in Ipomoea may also be mediated by ethylene.
In Arabidopsis, a mutant defective in anther dehiscence and flower opening was identified. The defect could be rectified by an exogenous application of jasmonic acid or linolenic acid. The mutated gene was a phospholipase, apparently involved in jasmonic acid synthesis. In some species, therefore, jasmonic acid may also be involved in flower opening (Ishiguro et al., 2001).
|
Regulation of opening and closure by external cues |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
Floral opening in several species is apparently independent of specific external regulation as it occurs at any time of the day. Floral opening in other species, belonging to a large number of families, show a relationship with the time of day. Flower closure may similarly be independent or dependent of the time of the day, depending on the species. This dependence on the time of the day may be regulated by external cues such as temperature, humidity, and light and/or by an internal rhythm.
Is flower opening due to changes in humidity, temperature or light?
Opening in many species occurs in the morning, correlated with an increase in temperature and light intensity, and with a decrease in ambient humidity. In species that open in the afternoon or at night, the movement is correlated with decreasing temperature and light intensity, and with an increase in humidity. Are these environmental changes, alone or in combination, adequate for opening?
Floral opening in most species tested did not react to changes in relative humidity (RH). Examples are Ipomoea purpureum, Taraxacum taraxacum (Hensel, 1905), Helianthemum guttatum (Davy de Virville and Obaton, 1922a), Turnera ulmifolia (Ball, 1933), Kalanchoë (Bünsow, 1953a), and Portulaca (Ichimura and Suto, 1998). Some exceptions are found in the Caryophyllaceae and Onagraceae. High humidity hastened opening of Silene saxifraga (Halket, 1931) and Lychnis dioica (Davy de Virville and Obaton, 1922b, 1923, 1924). According to Sigmond (1930a, b), opening in Oenothera biennis and O. lamarckiana was also advanced by placing flowers at high RH. Arnold (1959), in contrast, showed that opening of Oenothera berteriana and O. campylocalyx was not much influenced by RH. All species in which opening was advanced by high humidity are nocturnal. Only if the flower opens in the late afternoon or at night may the stimulating effect of high RH on opening have a biological role. Apparently, a positive effect on opening of a decrease in RH has not been reported, indicating that opening in the morning is generally independent of RH.
Both temperature and light clearly affect opening in several species. When Gentiana rhaetica plants, of which the flowers had closed during the night, were exposed to an increase in outside temperature from 7°C to 42°C, the flowers opened within 3 min. So in this species an increase in temperature was sufficient for opening (Kerner von Marilaun, 1891). Similarly, in Portulaca plants held at 20 °C, a rise in temperature was sufficient for rapid opening, although light intensified the response. Exposure to light without a temperature change did not result in full opening (Ichimura and Suto, 1998). Effects of light, however, must be interpreted with caution. In such experiments the flower temperature must be determined and if possible rigorously controlled. Depending on petal pigmentation and anatomy, light may increase petal temperature even at constant air temperature (McKee and Richards, 1998).
The opening of several flowers that bloom in spring also depends mainly on temperature. A small temperature rise in the morning was adequate for full opening of Ficaria, Galanthus, Tulipa, and Crocus. A detectable opening movement occurred by a rise of 0.2 °C in Crocus, whereas the minimum in Tulipa was 1 °C (Pfeffer, 1873; Andrews, 1929). Other species required a larger temperature difference. In order of decreasing sensitivity, Pfeffer (1904, page 494) mentioned Adonis vernalis, Ornithogalum umbellatum, Colchicum autumnale, Ranunculus ficaria, Anemone nemorosa, and Malope tifida. The latter species responded to a change of 5–10 °C. Temperature effects on opening may be due to an influence on a rapid growth process (as in the spring-blooming flowers already mentioned), or a stimulation of the basal growth rate. Hensel (1905) showed that high temperature promoted opening in Ipomoea purpurea, Linum usitatissimum, and Oxalis stricta, but the treatment had to last for several h and therefore apparently affected the basal growth rate.
Several other flowers respond mainly to light. Examples are Oxalis rosea, Nymphaea alba, and several species in the Asteraceae such as Leontodon spp. (Pfeffer, 1904, p. 494), Tragopogon brevirostre, and Bellis perennis (Oltmanns, 1895).
Two examples, showing the rather complex interplay of temperature and light on opening in some flowers, will be given. The capitulum of Taraxacum albidum opened in response to a rise in temperature, both in light and in darkness. Capitula also opened upon a change from darkness to light. Both temperature and light had an effect only at 18 °C or higher (Tanaka et al., 1987, 1988).
In Oxalis martiana a rise in temperature was sufficient for the opening of flowers on plants held in darkness. The required increase in temperature depended on the temperature at which the plants were held. Flowers on plants held continuously at 20 °C, for example, would be almost fully open within 3 h if the temperature rise was 10 °C (Tanaka et al., 1989). These effects may be explained by a ‘temperature sum’ as the degree of opening 3 h after a 5 °C increase at 20 °C was similar to that of 10 °C increase at 15 °C.
If the Oxalis plants were exposed to temperatures as described, but the light (about 12 W m–2) was also switched on, opening was hastened. In plants continuously held in darkness at 20 °C or 25 °C, light alone was sufficient for opening. Light had no effect in plants held at 15 °C or lower (Tanaka et al., 1989). These data suggest that the ambient temperature determined whether flower opening in this species depends on an increase in temperature, light or both.
Pfeffer (1873) observed that the effect of a rise in temperature, in temperature-sensitive day-blooming flowers, was much higher in the morning than in the evening. This time-dependence was also found in flowers that responded mainly to light. These results indicate that the effect of environmental factors on opening depend on the time since the last closure. As a rule, the reaction (to temperature or light) was greater the longer the flowers had been closed. This was corroborated by Oltmanns (1895) and by Stoppel and Kniep (1910).
Light also regulates the opening of some night-blooming species. In Oenothera lamarkiana light inhibited opening. Light was perceived by the lower third of the green sepals. Only wavelengths between 400 nm and 510 nm were effective, that is, the blue and green region of the spectrum (Saito and Yamaki, 1967). Blue light receptors are specifically effective at these wavelengths, thus may be involved in the inhibition of opening by light (Cashmore et al., 1999).
Effects of temperature and light on flower closure
In most species, flower closure responds to external factors in a way similar to opening. In some species, however, closure is apparently due to an endogenous rhythm even if opening is not. In still other species closure is due to senescence.
When senescence determines closure, it can be delayed by cool weather. Several ephemeral flowers can last for more than one day (or even several days) if the temperature is low (Burgerstein, 1901; Hensel, 1905; Davy de Virville and Obaton, 1922a). Hemerocallis (daylily), for example, which normally lasts one day, was open for two days in September and for three days by the end of October (Kerner von Marilaun, 1891).
Oltmanns (1895) showed, after detailed measurements, that the delay of closure in Lactuca sp. on overcast days was an effect of light, not of temperature. Field observations on some other species in the Asteraceae indicated the same effect of light. Flowers of Tragopogon brevirostre, for example, opened early in the morning and closed between 09.00 h and 10.00 h if the light intensity was relatively high, but they closed considerably later when the light intensity was lower. Burgerstein (1901) noted that flower closure during summer occurred earlier during the day, in several Asteraceae species, compared with closure during spring or autumn. Furthermore, experiments with Calendula arvensis showed closure following an increase in light intensity (Stoppel, 1910). The closing effect of high light intensity may not be limited to the Asteraceae, as a similar response was observed in Kalanchoë (Crassulaceae; Karvé et al., 1961).
Tulip and crocus are examples of flowers that close due to a temperature drop. The minimum decrease in temperature was about equal to the temperature rise required for opening (Pfeffer, 1873; Andrews, 1929).
Some Taraxacum spp. and Oxalis martiana are representatives of species where flower closure seems to be regulated by an endogenous rhythm (Tanaka et al., 1987, 1988, 1989). Although opening in three Taraxacum species depended on temperature and light, the time of capitulum closure was apparently independent of environmental conditions. Flowers of T. albidum and T. japonicum, for example, closed 8–11 h after the beginning of opening, both under natural conditions and under constant light and temperature (Tanaka et al., 1987, 1988).
These results show that opening and closure depend mainly on light and temperature, and that the effect of humidity seems restricted to some nocturnal species. The results also show that, in some species, a rather complicated interaction exists between the influence of light and temperature.
Regulation of opening and closure by duration of darkness and light
Several authors concluded that a minimum period of darkness was required for opening of day-bloomers in the light, and that a minimum period of light was necessary for their closure in darkness. Examples are Bellis perennis (Pfeffer, 1873), Tragopogon brevirostre (Oltmanns, 1895), and Kalanchoë (Bünsow, 1953a, b). Opening of Calendula arvensis, for example, required 3 h of darkness (Stoppel, 1910), whereas in Hedera helix the dark requirement was at least 5.5 h (Sigmond, 1929b). Artificial lighting during the night prevented flower opening in Turnera ulmifolia which required a few h of darkness prior to opening (Ball, 1933). These experiments are reminiscent of an effect of phytochrome. Indeed, in Ipomoea nil, flower opening was promoted by red light, and the effect of red light was reversed by a subsequent exposure to far-red light. The petals were found to be the sites of photoperception (Kaihara and Takimoto, 1980, 1981a, b). Perception of the duration of light or darkness may involve a relatively slow phytochrome reaction (Lumsden, 1991).
Reopening of Oxalis flowers exhibited a darkness and low temperature requirement. In flowers that had closed under continuous light, a minimum period of 1 h of darkness at 5 °C was required for full and rapid reopening in the light at 25 °C. However, this darkness/cold treatment was only effective if given more than 5 h after the flowers had fully closed in the light (Tanaka et al., 1989).
Hybrid tea roses open slowly—and only once—and terminate their life by petal abscission. When held at constant temperature and a 12 h light and dark cycle, full opening took a few days. Petal growth (and opening movement) was confined to about 5 h early in the morning. Growth started shortly before the lights were switched on. Placing rose flowers in continuous light or darkness immediately resulted in a steady slow growth rate. The results indicate that cyclic light and darkness was required for the periodicity of growth and opening (Evans and Reid, 1986, 1988). The onset of growth in rose flowers may require a minimum duration of darkness. Similarly, opening in Asiatic lily flowers (Lilium hybrid) started after about 7 h of darkness. Flowers held in continuous darkness showed irregular opening, indicating that one change of light to darkness (and possibly a minimum duration of darkness) was necessary for the timing of opening (Bieleski et al., 2000a).
The requirement of a period of darkness for opening and a period of light for closure may be part of an endogenous rhythm. In Hedera helix, for example, opening and closure depended on changes from light to dark and vice versa. Under natural conditions this leads to a 24 h rhythm, whereby opening occurs about 12 h after the onset of darkness. Despite this rhythm, opening also occurred after shorter periods of darkness, but at least about 6 h of darkness were required, after 12 h of light (Sigmond, 1929b).
|
Repeated opening and closure, role of endogenous rhythms |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
The presence of an endogenous rhythm of opening and closure is usually tested by placement in constant darkness or constant light. In all species investigated, the rhythm, if it existed, continued for some time under constant light or darkness, but it was also much affected by changes from light to darkness or vice versa.
Examples of species with an endogenous rhythm are the day-bloomers Calendula arvensis, Bellis perennis (Stoppel, 1910; Stoppel and Kniep, 1910), Hedera helix (Sigmond, 1929a), and Kalanchoë blossfeldiana (Bünsow, 1953a, b). It was also found in the night-bloomers Cestrum nocturnum (Overland, 1960), Cereus grandifolius (Schmucker, 1928) and several species in the genus Oenothera (Arnold, 1959; Takimoto, 1986; Sigmond, 1930a, b). Calendula arvensis is taken as an example and briefly compared with some of the other species.
When grown outdoors, the flowers of C. arvensis open in the morning and close in the afternoon, for about 5 d prior to petal wilting. Temperature changes had no effect on opening or closure. Under continuous darkness, opening and closure showed a 24 h rhythm. When the leaves were subjected to a different day/night cycle from the flowers, the opening and closing rhythm followed that of the flowers. The 24 h rhythm in continuous darkness also occurred in plants that had previously been subjected to a day/night cycle of 6 h rather than 12 h, in plants that had been held under continuous light, and in plants previously subjected to irregular periods of light and darkness. The flowers thus show a rhythm based on a clock that apparently resides in the flower, and which is unaffected by the light/dark regime prior to continuous darkness.
The time of the onset of darkness, however, had a large effect on the rhythm. In plants grown in the field and brought into 12 h darkness, starting at 12 noon, the flowers from then on showed a 24 rhythm whereby they followed the new cycle. Normally all flowers on a plant opened and closed at the same time. However, if buds on the same plant were placed in darkness at various times, they opened and closed at different times, set by the time of the onset of continuous darkness. This effect was also observed if closed buds were placed in darkness, so the endogenous rhythm can be set at a rather early stage of development. By contrast, in flowers that had already opened and assumed a specific rhythm, it was almost impossible to change the phase.
In light/dark (LD) cycles of 6 h or 9 h, flower opening followed the imposed cycle (i.e. they were 6 h open and 6 h closed, etc). Interestingly, if the light and dark periods were made as short as 2 h, the flowers again showed a 24 h rhythm. Within limits, therefore, the endogenous rhythm can become entrained by shorter light/dark cycling. Entrainment is defined as the process whereby the plant, exposed to repeated periods of light and darkness with a period P, changes its rhythm to the same period.
Similar results were obtained with Bellis perennis, which showed an endogenous rhythm only in continuous light (Stoppel, 1910) and in Kalanchoë blossfeldiana, where the rhythm occurred both in continuous light and continuous darkness. When the latter was subjected to light and dark periods of 10 h, 8 h and 6 h, the rhythm followed the newly imposed cycle. When the light and dark periods were as short as 4 h or 2 h, the flowers again showed a 24 h cycle (Bünsow, 1953a, b). The time of transfer to continuous darkness or continuous light would set the phase of the endogenous rhythm (Karvé et al., 1961; Zimmer, 1962).
When plants of Cereus grandifolius (a night-bloomer) were kept in darkness during the day and exposed to light at night, the normal periodicity was retained for some days but gradually became weaker, and then assumed a new phase in which opening occurred at the end of the light period (Schmucker, 1928). Similar observations were made in Oenothera berteriana, O. campylocalyx (Arnold, 1959), and O. lamarckiana (Takimoto, 1986).
Circadian rhythms in flower opening and closure are thus highly dependent on changes from light to darkness (and/or vice versa). In the species tested, light was invariably the entrainment stimulus. Work on rhythms in other plant parts shows that temperature can also be such a stimulus (Bünning, 1973; Hayama and Coupland, 2003). A temperature-dependent endogenous rhythm may therefore also exist in flower opening and closure, but if it does it seems to be rare.
|
Control mechanisms: the molecular basis |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
The molecular control of opening and closure, at specific times of the day, is currently unknown. This is true both for single opening and closure, for repeated movements for which no evidence of an endogenous rhythm exists, and for repeated movements in which such a rhythm is apparently involved. Nonetheless, the circadian clock of plants is currently being dissected and this evidence may be helpful for hypothesis formation.
The advantages of Arabidopsis mutants have not, as yet, been employed to study the timing mechanism of floral opening and closure. In the laboratory, flowers of A. thaliana open in the morning, shortly after the lights are switched on, and they close at about midday. These movements are repeated for 2–3 d, until the petals are shed almost turgid. Mutants with another pattern of floral opening and closure have apparently not been selected (G Angenent, personal communication 2003). Circadian leaf movements have been studied in some detail in Arabidopsis mutants (Michaels and Amasino, 1999; Swarup et al., 1999; Yanovsky et al., 2001; Staiger et al., 2003). One out-of-phase mutant has been characterized in which the peaks of leaf movement occurred 3.6 h earlier than normal (Salomé et al., 2002). The mechanism and control of these leaf movements may be similar to that of petal movements involved in flower opening and closure. However, the relevance of the data on leaf movements for floral opening and closure has yet to be established.
In Arabidopsis, the expression of several genes depends on the time of day. A 6 h interval microarray, involving more than 7000 genes, showed that about 2% cycled with a circadian rhythm (Schaffer et al., 2001). In Arabidopsis and other plants, several genes with a circadian expression pattern have been identified, for example, a catalase (Kwon and An, 2001), cysteine protease (Ueda et al., 2000), a putative ß-amylase (Chandler et al., 2001), nitrate reductase (Tucker et al., 1998), sucrose phosphate synthase (Rufty et al., 1983), and chlorophyll a/b binding proteins (Cab) of photosystems I and II (Riesselmann and Piechulla, 1990; McClung, 2000). Interestingly, Thain et al. (2000) showed that the circadian rhythm of Cab gene expression can be set to different phases in various parts of the plants, and even within the same leaf, using localized dark/light treatments. The clock in each cell apparently functions independently of that of neighbouring cells. This agrees with the results on flower opening in Calendula arvensis, described above: buds on the same plant, placed in darkness at various times, opened and closed at different times, set by the time of the onset of continuous darkness (Stoppel, 1910; Stoppel and Kniep, 1910).
The expression pattern of Cab genes in tomato is surprisingly similar to the characteristic of the endogenous rhythm of flower opening (especially that of Calendula, Bellis, and Kalanchoë). Under a 12 h LD cycle Cab was increasingly expressed towards the end of the dark period. The peak of expression could be entrained to LD cycles of various lengths, even to one as short as 6 h light and 6 h darkness. Under constant light, the rhythm levelled off and its phases increased, but 3 h of darkness and subsequent light brought it back to a 24 h cycle with large amplitudes. A new phase was then observed, which depended on the time of switching the lights on (Piechulla, 1989; Riesselmann and Piechulla, 1990). A deletion analysis of the promotor of the Cab genes (more recently designated light-harvesting-complex genes) showed a sequence of 47 nucleotides that is necessary for conferring circadian oscillations. Part of this sequence overlaps with a known sequence for phytochrome-mediated gene expression (Piechulla et al., 1998).
Circadian fluctuations in hormone production have also been observed. In cotton cotyledons, for example, ethylene production rose at the end of the darkness period, under a 12 h LD cycle. Production reached a maximum early during the next light period. The results indicated that the fluctuation in ethylene release was not due to a rhythm in stomatal opening (Rikin et al., 1984). In sorghum seedlings an ethylene rhythm was related to circadian expression of the mRNA for ACC oxidase (Finlayson et al., 1999). A similar rhythm was observed in gibberellin biosynthesis in sorghum (Foster and Morgan, 1995). The floral stem of Arabidopsis showed a circadian pattern of elongation growth, related to a circadian oscillation of IAA concentrations. Auxin transport inhibitors abolished the growth oscillation (Jouve et al., 1999). Such circadian fluctuations in hormone levels have not, as yet, been investigated in relation to flower opening and closure.
A few questions still remain largely unanswered: what is the nature of the circadian oscillator and the light sensor, and what is the signal transduction pathway? Two closely related (MYB-type) DNA-binding proteins (designated CCA1 and LHY) have been identified in Arabidopsis, which regulate the expression of light-harvesting-complex genes and are connected to circadian leaf movements. Both genes showed a circadian expression pattern. Mutant genes were expressed at a constant high level, which suggested that they were part of a feedback circuit that regulates its own expression. The two genes are therefore either part of the central oscillator of the circadian clock, or are closely associated with it. Another protein, designated TOC1, seems also part of the circadian oscillator. Overexpression of TOC1 completely abolished circadian rhythms in the expression of a number of genes (Yanovsky and Kay, 2001; Hayama and Coupland, 2003).
At least one of these proteins (CCA1) bound to a region of the Arabidopsis light-harvesting-complex promoter that is necessary for its phytochrome responsiveness. Phytochrome also affected the expression of the CCA1 gene itself: expression was affected by light signals known to reset the clock (Wang and Tobin, 1998; Schaffer et al., 1998). Several reports now point to phytochromes A, B, D, and E as sensors for setting circadian rhythms in Arabidopsis (Yanovsky and Kay, 2001; Wang and Deng, 2003). In addition, specific blue light receptors (Cryptochromes 1 and 2) are involved in the input of blue light into the circadian rhythms in Arabidopsis (Cashmore et al., 1999; Yanovsky and Kay, 2001).
As Arabidopsis flowers open and close in a circadian fashion, the numerous mutants that have been used to investigate the circadian clock, and the input of light and temperature to the clock, may prove useful for the further study of flower opening and closure.
|
Strategies of flower opening and closure |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
It is not clear, from an ecological and evolutionary point of view, why some flowers last as long as they do (Ashman and Schoen, 1994; van Doorn, 1997b), nor is it obvious why they open and close as they do. Opening and closure show a wide range of strategies. Presumably, these strategies have been selected to optimize reproductive success at a minimal (metabolic) cost. Relatively easy to explain from a selective point of view it seems, is the existence of night-bloomers that are pollinated by a small group of nocturnal animals only. The time that pollinators are active may obviously exert selective pressure. An initial simulation model dealt with the efficiencies of pollen removal and pollen deposition, estimated from field data on Lonicera japonica. The flower opens in the evening and stays open for several nights and days. According to the model, anthesis at dusk rather than in the morning was favoured in this species, as long as pollen deposition efficiency of nocturnal pollinators was higher than that of day pollinators, even when day pollinators transferred more pollen (Miyake and Yahara, 1999).
Several flowers remain open day and night, although they are pollinated only during the day or night. This may, at least in some species, relate to a circadian pattern of scent production. In Petunia, for example, the flower scents only during the night, which may explain, at least partially, why it is usually only pollinated by moths. Not all open flowers smell. Perhaps, at least in some species, circadian floral opening and closure may be an adaptation that avoids the cost of scent production?
Flowers occur in a vast range of ecological situations. It is unsurprising, therefore, to find different ambient factors which regulate opening and closure, but these have not been categorized to their ecological niches, nor have they been explained in terms of selective advantages. May, for example, the tendency of early-spring flowering species such as tulip and crocus to close after a drop in temperature relate to protection of the reproductive parts from being covered in snow, or from being damaged by hail or rain, at a time when pollinator activity is low?
Among the flowers that show repeated opening and closure, some open irregularly, only if the temperature is high and/or the sun is shining (such as dandelion), whereas others open and close at regular intervals. In general, the advantage of regular flower closure is not very clear. So far, some hypotheses have been put forward but these have not been tested. Closure, for example, may aid in pollination as it traps pollinating insects (e.g. in fig species and Nymphaea spp.). Kerner von Marilaun (1891) thought that flower closure during the night may avoid pollen wetting. His idea may be extended to flowers of species such as dandelion, which open only if the weather is fine. Pfeffer (1904, p.481) suggested that intermittent flower closure may help to exclude insects, may protect against cold or avoid damage by high light intensity.
In addition, regular closure may limit water loss and limit the entry of potentially harmful micro-organisms. Limitation of flower opening to periods of pollinator activity may reduce the risk of entry of airborne pathogens and avoid the risk of pathogens being delivered by non-pollinating insects. Bacteria and fungi usually do not grow on dry petal tissues, but the presence of water (for example dew) on the flowers, or high ambient humidity, expedites fungal and bacterial growth. Flowers that avoid wetting by rain or dew, or avoid opening at times of very high humidity, seem therefore better adapted. This may explain why several flowers open when the morning dew has already disappeared, and why some nocturnal flowers close before the dew occurs.
|
Conclusions |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
In most species, flower opening is due to (local) elongation growth or to local ion accumulation that is not accompanied by growth. The elongation growth of petals, leading to opening, does not seem different from that in other plant parts, as it requires a source of energy and cell wall loosening and expansion.
Cell elongation during flower opening stands out, firstly, by its high rate, and, secondly, by its rather specific regulation. The timing of opening is regulated by factors such as temperature, the quality and quantity of light, and the duration of both light and darkness. Flower closure, if it occurs, may be related to senescence or an active process. In the latter case, it is often regulated in a way similar to that of opening.
In a few species the requirements for repeated opening and closure, and the role of an endogenous rhythm, have been elucidated. The phase of the endogenous rhythms can be altered by a single switch from light to darkness (or vice versa). Thus far, only a few reports hint at the nature of the sensor of the light stimuli. Results in only one species (Ipomoea nil) suggest a role of phytochrome, and perhaps a blue light receptor is involved in the inhibition, during the day, of opening in a nocturnal species (Oenothera lamarkiana).
The co-ordination of processes culminating in synchronized flower opening is, in many species, highly intricate. This complex control by endogenous and exogenous factors sets flower opening and closure apart from most other growth processes. Although some of the interplay between the various environmental and internal factors is now known, mainly by observing opening and closure as a phenotype, little is known of the cellular and molecular mechanisms behind it. At least in Arabidopsis this may rapidly change. Its flowers open and close for a few days according to a circadian rhythm. There are now many Arabidopsis mutants that have been related to the circadian clock and its light input. It is suggested that these be used for the further study of circadian flower opening and closure.
|
Acknowledgement |
|---|
We thank Dr Tony Stead (Royal Holloway, University of London) for critically reading the manuscript.
|
References |
|---|
|
TopAbstractIntroductionVarieties of flower opening...Mechanism of opening and...Regulation of opening and...Repeated opening and closure,...Control mechanisms: the...Strategies of flower opening...ConclusionsReferences |
|---|
Andrews FM. 1929. The effect of temperature on flowers. Plant Physiology 4, 281–284.
Arnold CG. 1959. Blütenöffnung bei Oenothera in Abhängingkeit vom Licht-Dunkelrhythmus. Planta 53, 198–211.[CrossRef][Web of Science]
Ashman TL, Schoen DJ. 1994 How long should flowers live? Nature 371, 788–791. [See also criticism by Shykoff et al. 1996 in Nature 379, 779; and by van Doorn WG, 1996 in Nature 379, 779–780.]
Ball NG. 1933. A physiological investigation of the ephemeral flowers of Turnera ulmifolia. New Phytologist 32, 13–36.[CrossRef]
Becker T. 1953. Wuchsstoff- und Säureschwankungen bei Kalanchoë blossfeldiana in verschiedenen Licht-Dunkelwechseln. Planta 43, 1–12.[Medline]
Bieleski R. 1993. Fructan hydrolysis drives petal expansion in the ephemeral daylily flower. Plant Physiology 103, 213–219.[Abstract]
Bieleski R, Elgar J, Heyes J, Woolf A. 2000a. Flower opening in Asiatic lily is a rapid process controlled by dark–light cycling. Annals of Botany 86, 1169–1174.
Bieleski R, Elgar J, Heyes J. 2000b. Mechanical aspects of rapid flower opening in Asiatic lily. Annals of Botany 86, 1175–1183.
Böhner P. 1934. Zur Thermonastie der Tulpenblüte. Berichte der Deutschen Botanischen Gesellschaft 52, 336–347.
Brummel DA, Harpster MH, Dunsmuir P. 1999. Differential expression of expansin gene family members during growth and ripening of tomato fruit. Plant Molecular Biology 39, 161–169.[CrossRef][Web of Science][Medline]
Bünning E. 1929. Über die thermonastischen und thigmonastischen Blütenbewegungen. Planta 8, 698–716.[CrossRef]
Bünning E. 1973. The physiological clock, 3rd edn. New York: Springer.
Bünsow R. 1953a. Endogene Tagesrhythmik und Photoperiodismus bei Kalanchoë blossfeldiana. Planta 42, 220–252.[Medline]
Bünsow R. 1953b. Über den Einfluss der Lichtmenge auf die endogene Tagesrhythmik bei Kalanchoë blossfeldiana. Biologisches Zentralblatt 72, 465–477.
Burgerstein A. 1901. A. v. Kerner’s Beobachtungen über die Zeit des Öffnens und Schliessens von Blüten. Österreichische Botanische Zeitschrift 51, 185–193.[CrossRef]
Cashmore AR, Jarillo JA, Wu YJ, Liu D. 1999. Cryptochromes: blue light receptors for plants and animals. Science 284, 760–765.
Chandler JW, Apel K, Melzer S. 2001. A novel putative beta-amylase gene and Atbeta-Amy from Arabidopsis are circadian regulated. Plant Science 161, 1019–1024.[CrossRef][Web of Science]
Claus G. 1926. Die Blütenbewegungen der Gentianaceen. Flora 120, 198–226.
Collier DE. 1997. Changes in respiration, protein and carbohydrates of tulip tepals and Alstroemeria petals during development. Journal of Plant Physiology 150, 446–451.[CrossRef][Web of Science]
Cosgrove DJ. 1999. Enzymes and other agents that enhance cell wall extensibility. Annual Reviews of Plant Physiology and Plant Molecular Biology 50, 391–417.[CrossRef][Web of Science][Medline]
Cushman LC, Pemberton HB, Kelly JW. 1994. Cultivar, flower stage, silver thiosulfate and BA interactions affect performance of potted miniature roses. HortScience 29, 805–808.[Web of Science]
Davy de Virville A, Obaton F. 1922a. Observations et expériences sur les fleurs éphémères. Comptes Rendus des Séances de l’Académie des Sciences (suppl. series A–D) 175, 637–640.
Davy de Virville A, Obaton F. 1922b. Sur l’ouverture et la fermeture des fleurs météoriques persistantes. Comptes Rendus des Séances de l’Académie des Sciences (suppl. series A–D) 175, 841–843.
Davy de Virville A, Obaton F. 1923. Étude biologique de l’épanouissement des fleurs. I. Revu Générale de Botanique 35, 161–185.
Davy de Virville A, Obaton F. 1924. Étude biologique de l’épanouissement des fleurs. II. Revu Générale de Botanique 36, 49–69.
de Vetten NC, Huber DJ. 1990. Cell wall changes during the expansion and senescence of carnation (Dianthus caryophyllus) petals. Physiologia Plantarum 78, 447–454.[CrossRef]
Eason JR, de Vre LA, Somerfield SD, Heyes JA. 1997. Physiological changes associated with Sandersonia aurantiaca flower senescence in response to sugar. Postharvest Biology and Technology 12, 43–50.[CrossRef][Web of Science]
Evans RY, Reid MS. 1986. Control of petal expansion during diurnal opening of roses. Acta Horticulturae 181, 55–63.
Evans RY, Reid MS. 1988. Changes in carbohydrates and osmotic potential during rhythmic expansion of rose petals. Journal of the American Society for Horticultural Science 113, 884–888.
Finlayson SA, Lee IJ, Mullet JE, Morgan PW. 1999. The mechanism of rhythmic ethylene production in sorghum. The role of phytochrome B and simulated shading. Plant Physiology 119, 1083–1089.
Foster KR, Morgan PW. 1995. Genetic regulation of development in Sorghum bicolor. IX. The ma3 allele disrupts diurnal control of gibberellin biosynthesis. Plant Physiology 108, 337–343.[Abstract]
Griesel WO. 1954. Retardation of maturation in Magnolia flowers by maleic hydrazide. Science 119, 843–45.
Halket AC. 1931. The flowers of Silene saxifraga L.; an inquiry into the cause of their day closure and the mechanism concerned in effecting their periodic movements. Annals of Botany 45, 15–37.
Hammond JBW. 1982. Changes in amylase activity during rose bud opening. Scientia Horticulturae 16, 283–289.[CrossRef]
Hayama R, Coupland G. 2003. Shedding light on the circadian clock and the photoperiodic control of flowering. Current Opinion in Plant Biology 6, 13–19.[CrossRef][Web of Science][Medline]
Hensel EP. 1905. On the movements of petals. Nebraska University Studies 5, 191–228.
Ho LC, Nichols R. 1977. Translocation of 14C-sucrose in relation to changes in carbohydrate content in rose corollas cut at different stages of development. Annals of Botany 41, 227–242.
Horie K. 1961. The behavior of the petals in the fading of the flowers of Tradescantia reflexa. Protoplasma 53, 377–386.[CrossRef][Web of Science]
Ichimura K, Suto K. 1998. Environmental factors controlling flower opening and closing in a Portulaca hybrid. Annals of Botany 82, 67–70.
Ishiguro S, Kawai OA, Ueda J, Nishida I, Okada K. 2001. The defective in anther dehiscence 1 gene encodes a novel phospholipase A1 catalyzing the initial step of jasmonic acid biosynthesis, which synchronizes pollen maturation, anther dehiscence, and flower opening in Arabidopsis. The Plant Cell 13, 2191–2209.
Jouve L, Gaspar T, Kevers C, Greppin H, Degli Agosti R. 1999. Involvement of indole-3-acetic acid in the circadian growth of the first internode of Arabidopsis. Planta 209, 136–142.[CrossRef][Web of Science][Medline]
Kaihara S, Takimoto A. 1980. Studies on the light controlling the time of flower-opening in Pharbitis nil. Plant and Cell Physiology 21, 21–26.[Medline]
Kaihara S, Takimoto A. 1981a. Effects of light and temperature on flower-opening in Pharbitis nil. Plant and Cell Physiology 22, 215–221.
Kaihara S, Takimoto A. 1981b. Physical basis of flower opening in Pharbitis nil. Plant and Cell Physiology 22, 307–310.
Kaihara S, Takimoto A. 1983. Effect of plant growth regulators on flower opening of Pharbitis nil. Plant and Cell Physiology 24, 309–316.
Karvé A, Engelmann W, Schoser G. 1961. Initiation of rhythmical petal movements in Kalanchoë blossfeldiana by transfer from continuous darkness to continuous light or vice versa. Planta 56, 700–711.[CrossRef][Web of Science]
Kerner von Marilaun A. 1891. Pflanzenleben, Band 2. Leipzig: Verlag des Bibliographisches Institut.
Koning RE. 1984. The role of plant hormones in the growth of the corolla of Gaillardia grandiflora (Asteraceae) ray flowers. American Journal of Botany 71, 1–8.[CrossRef][Web of Science]
Koning RE. 1986. The role of ethylene in corolla unfolding in Ipomoea nil (Convolvulaceae). American Journal of Botany 73, 152–155.[CrossRef][Web of Science]
Kraus C. 1879. Beiträge zur Kenntniss der Bewegungen wachsender Laub- und Blüthenblätter. Flora 62, 11–16, 27–44, 55–80, 90–94.
Kuiper D, van Reenen HS, Ribot SA. 1991. Effect of gibberellic acid on sugar transport into petals of ‘Madelon’ rose flowers during bud opening. Acta Horticulturae 298, 93–98.
Kwon SI, An CS. 2001. Molecular cloning, characterization and expression analysis of a catalase cDNA from hot pepper (Capsicum annuum L.). Plant Science 160, 961–969.[CrossRef][Web of Science][Medline]
Lindman CAM. 1897. Remarques sur la floraison du genre Silene L. Acta Horti Bergiani 3, 3–28.
Lumsden PJ. 1991. Circadian rhythms and phytochrome. Annual Reviews of Plant Physiology and Plant Molecular Biology 42, 351–371.[CrossRef][Web of Science]
Marissen N. 1991. Osmotic potential and carbohydrate contents in the corolla of the rose cv. Madelon. Acta Horticulturae 298, 145–152.
McClung CR. 2000. Circadian rhythms in plants: a millennial view. Physiologia Plantarum 109, 359–371.[CrossRef]
McKee J, Richards AJ. 1998. Effect of flower structure and flower colour on intrafloral warming, pollen germination and pollen tube growth in winter-flowering Crocus L. (Iridaceae). Botanical Journal of the Linnean Society 128, 369–384.[Web of Science]
Michaels S, Amasino R. 1999. Flowering Locus C encodes a novel MADS domain protein that acts as a repressor of flowering. The Plant Cell 11, 949–956.
Miyake T, Yahara T. 1999. Theoretical evaluation of pollen transfer by nocturnal and diurnal pollinators: when should a flower open? Oikos 86, 233–240.[CrossRef][Web of Science]
O’Donoghue EM, Somerfield SD, Heyes JA. 2002a. Organization of cell walls in Sandersonia aurantiaca floral tissue. Journal of Experimental Botany 53, 513–523.
O’Donoghue EM, Somerfield SD, Heyes JA. 2002b. Vase solutions containing sucrose result in changes to sandersonia (Sandersonia aurantiaca) flowers. Postharvest Biology and Technology 26, 285–294.[CrossRef][Web of Science]
Overland L. 1960. Endogenous rhythm in opening and odor of flowers of Cestrum nocturnum. American Journal of Botany 47, 378–382.[CrossRef][Web of Science]
Oltmanns F. 1895. Über das Öffnen und Schliessen der Blüten. Botanische Zeitung 53, 31–52.
Panavas T, Reid PD, Rubinstein B. 1998. Programmed cell death of daylily petals: activities of wall-based enzymes and effects of heat shock. Plant Physiology and Biochemistry 36, 379–388.[CrossRef][Web of Science]
Pfeffer W. 1873. Untersuchungen über Öffnen und Schliessen der Blüten. In: Physiologische Untersuchungen. Leipzig: Wilhelm Engelmann, 161–216.
Pfeffer W. 1904. Pflanzenphysiologie. Ein Handbuch der Lehre vom Stoffwechsel und Kraftwechsel in der Pflanze. Leipzig: Wilhelm Engelmann.
Phillips HL, Kende H. 1980. Structural changes in flowers of Ipomoea tricolor during flower opening and closing. Protoplasma 102, 199–216.[CrossRef][Web of Science]
Piechulla B. 1989. Changes of the diurnal and circadian (endogenous) mRNA oscillations of the chlorophyll a/b binding protein in tomato leaves during altered day/night (light/dark) regimes. Plant Molecular Biology 12, 317–327.[CrossRef][Web of Science]
Piechulla B, Merforth N, Rudolph B. 1998. Identification of tomato Lhc promotor regions necessary for circadian expression. Plant Molecular Biology 38, 655–662.[CrossRef][Web of Science][Medline]
Raab MM, Koning RE. 1987. Interacting roles of gibberellin and ethylene in corolla expansion of Ipomoea nil (Convolvulaceae). American Journal of Botany 74, 921–927.[CrossRef][Web of Science]
Reid MS, Evans RY. 1986. Control of cut flower opening. Acta Horticulturae 181, 45–54.
Reid MS, Evans RY, Dodge LL, Mor Y. 1989. Ethylene and silver thiosulphate influence opening of cut rose flowers. Journal of the American Society for Horticultural Science 114, 436–440.
Riesselmann S, Piechulla B. 1990. Effect of dark phases and temperature on the chlorophyll a/b binding protein mRNA level oscillations in tomato seedlings. Plant Molecular Biology 14, 605–616.[CrossRef][Web of Science][Medline]
Rikin A, Chalutz E, Anderson JD. 1984. Rhythmicity in ethylene production in cotton seedlings. Plant Physiology 75, 493–495.
Rufty TW, Kerr PS, Huber SC. 1983. Characterization of diurnal changes in activities of enzymes involved in sucrose biosynthesis. Plant Physiology 73, 428–433.
Saito M, Yamaki T. 1967. Retardation of flower opening in Oenothera lamarckiana caused by blue and green light. Nature 214, 1027.
Salomé PA, Michael TP, Kearns EV, Fett-Neto AG, Sharrock RA, McClung CR. 2002. The out of phase 1 mutant defines a role for PHYB in circadian phase control in Arabidopsis. Plant Physiology 129, 1674–1685.
Schaffer R, Landgraf J, Accerbi M, Simon V, Larson M, Wisman E. 2001. Microarray analysis of diurnal and circadian-regulated genes in Arabidopsis. The Plant Cell 13, 113–123.
Schaffer R, Ramsay N, Samach A, Corden S, Puterill J, Carre IA, Coupland G. 1998. The late elongated hypocotyl mutation of Arabidopsis disrupts circadian rhythms and the photoperiodic control of flowering. Cell 93, 1219–1229.[CrossRef][Web of Science][Medline]
Schmucker T. 1928. Die Bedingungen des nächtlichen Blühens von Cereus grandiflorus. Planta 5, 549–559.[CrossRef]
Schrempf M. 1977. Studies on the circadian rhythm of petal movement in Kalanchoë blossfeldiana. Journal of Interdisciplinary Cycle Research 8, 396–400.[Web of Science]
Schrempf M. 1980. The action of abscisic acid on the circadian petal movement of Kalanchoë blossfeldiana. Zeitschrift für Pflanzenphysiologie 100, 397–407.[Web of Science]
Serek M, Jones RB, Reid MS. 1994. Role of ethylene in opening and senescence of Gladiolus sp. flowers. Journal of the American Society for Horticultural Science 119, 1014–1019.
Sigmond H. 1929a. Vergleichende Untersuchungen über die Anatomie und Morphologie von Blütenknospenverschlüssen. Beihefte des Botanisches Zentralblatt 46, 1–67.
Sigmond H. 1929b. Über das Aufblühen von Hedera helix L. und die Beeinflussung dieses Vorganges durch das Licht. Beihefte des Botanisches Zentralblatt 46, 68–92.
Sigmond H. 1930a. Die Entfaltung de Blütenknospe zweier Oenothera-Arten. Teil I. Beihefte des Botanisches Zentralblatt 46, 476–488.
Sigmond H. 1930b. Die Entfaltung de Blütenknospe zweier Oenothera-Arten. Teil II. Beihefte des Botanisches Zentralblatt 47, 69–138.
Solhaug KA, Aares E. 1994. Remobilization of fructans in Phippsia algida during rapid inflorescence development. Physiologia Plantarum 91, 219–225.[CrossRef]
Staiger D, Allenbach L, Salathia N, Fiechter V, Davis SJ, Millar AJ, Chory J, Fankhauser C. 2003. The Arabidopsis SRR1 gene mediates phyB signaling and is required for normal circadian clock function. Genes and Development 17, 256–268.
Steinitz B, Cohen A. 1982. Gibberellic acid promotes flower bud opening on detached flower stalks of statice (Limonium sinuatum L.). HortScience 17, 903–904.[Web of Science]
Stoppel R. 1910. Über den Einfluss des Lichtes auf das Öffnen und Schliessen einiger Blüten. Zeitschrift für Botanik 2, 367–453.
Stoppel R, Kniep H. 1910. Weitere Untersuchungen über das Öffnen und Schliessen der Blüten. Zeitschrift für Botanik 3, 369–399.
Sturm A. 1999. Invertases: primary stuctures, functions and roles in plant development and sucrose partitioning. Plant Physiology 121, 1–7.
Swarup K, Alonso BC, Lynn JR, Michaels SD, Amasino RM, Koornneef M, Millar AJ. 1999. Natural allelic variation identifies new genes in the Arabidopsis circadian system. The Plant Journal 20, 67–77.[CrossRef][Web of Science][Medline]
Takimoto A. 1986. Oenothera. In: Halevy AH, ed. Handbook of flowering, Vol. 5. Boca Raton, FL: CRC Press, 231–236.
Tanaka O, Murakami H, Wada H, Tanaka Y, Naka Y. 1989. Flower opening and closing of Oxalis martiana. Botanical Magazine Tokyo 102, 245–254.[CrossRef][Web of Science]
Tanaka O, Tanaka Y, Wada H. 1988. Photonastic and thermonastic opening of capitulum in dandelion, Taraxacum officinale and Taraxacum japonicum. Botanical Magazine Tokyo 101, 103–110.[CrossRef][Web of Science]
Tanaka O, Wada H, Yokoyama T, Murakami H. 1987. Environmental factors controlling capitulum opening and closing of dandelion, Taraxacum albidum. Plant and Cell Physiology 28, 727–730.
Thain SC, Hall A, Millar AJ. 2000. Functional independence of circadian clocks that regulate plant gene expression. Current Biology 10, 951–956.[CrossRef][Web of Science][Medline]
Tjosvold SA, Wu MJ, Reid MS. 1995. Reduction of post-production quality loss in potted miniature roses. Acta Horticulturae 405, 408–414.
Trolinder NL, McMichael BL, Upchurch DR. 1993. Water relations of cotton flower petals and fruit. Plant, Cell and Environment 16, 755–760.[CrossRef]
Trusty SE, Miller WB. 1991. Postproduction carbohydrate levels in pot chrysanthemums. Journal of the American Society for Horticultural Science 116, 1013–1018.
Tucker DE, Ort DR, Garab G. 1998. The circadian rhythm in the expression of nitrate reductase in tomato is driven by changes in protein level and not by protein phosphorylation. In: Proceedings of the XIth International Congress on Photosynthesis, Budapest, Vol. V. Dordrecht (The Netherlands): Kluwer, 3749–3754.
Ueda T, Seo S, Ohashi Y, Hashimoto J. 2000. Circadian and senescence enhanced expression of a tobacco cysteine protease gene. Plant Molecular Biology 44, 649–657.[CrossRef][Web of Science][Medline]
van der Meulen-Muisers JJM. 2000. Genetic and physiological aspects of postharvest flower longevity in Asiatic hybrid lilies (Lilium L.). PhD thesis, Wageningen University, The Netherlands, 75–87.
van der Meulen-Muisers JJM, van Oeveren JC, Meijkamp BB, Derks FHM. 1995. Effect of floral bud reduction on individual flower longevity in Asiatic hybrid lilies. Acta Horticulturae 405, 46–57.
van Doorn WG. 1997a. Water relations of cut flowers. Horticultural Reviews 18, 1–85.[Medline]
van Doorn WG. 1997b. Effects of pollination on floral attraction and longevity. Journal of Experimental Botany 48, 1615–1622.
van Meeteren U, van Gelder H, van de Peppel AC. 1995. Aspects of carbohydrate balance during floret opening in freesia. Acta Horticulturae 405, 117–122.
van Meeteren U, van de Peppel AC, van Gelder H. 2001. DOCIS: a model to simulate carbohydrate balance and development of inflorescence during vase life. Acta Horticulturae 543, 359–365.
Vergauwen R, van den Ende W, van Laere A. 2000. The role of fructan in flowering of Campanula rapunculoides. Journal of Experimental Botany 51, 1261–1266.
Wang ZY, Tobin EM. 1998. Constitutive expression of the circadian clock asscociated 1 (CCA 1) gene disrupts circadian rhythms and suppresses its own expression. Cell 93, 1207–1217.[CrossRef][Web of Science][Medline]
Wang H, Deng XW. 2003. Dissecting the phytochrome A-dependent signaling network in higher plants. Trends in Plant Science 8, 172–178.[CrossRef][Web of Science][Medline]
Wiedersheim W. 1904. Studien über photonastische und thermonastische Bewegungen. Jahrbücher für wissenschaftliche Botanik 40, 230–241.
Wiemken-Gehrig V, Wiemken A, Matile P. 1974 Mobilization von Zellwandstoffen in der welkenden Blüte von Ipomoea tricolor Cav. Planta 115, 297–307.
Winkenbach F. 1971. Zum Stoffwechsel der aufblühenden und welkenden Korolle der Prunkwinde Ipomoea purpurea. I. Beziehungen zwischen Gestaltwandel, Stofftransport, Atmung und Invertase-aktivität. Berichte der Schweizerischen Botanischen Gesellschaft 80, 374–390.
Winkenbach F, Matile P. 1970. Evidence for de novo synthesis of an invertase inhibitor in senescing petals of Ipomoea. Zeitschrift für Pflanzenphysiologie 63, 292–295.[Web of Science]
Wood WML. 1953. Thermonasty in tulip and crocus flowers. Journal of Experimental Botany 4, 65–77.[Medline]
Woodson WR, Wang H. 1987. Invertases of carnation petals. Partial purification, characterization and changes in activity during petal growth. Physiologia Plantarum 71, 224–228.[CrossRef]
Yamane K, Kawabata S, Sakiyama R. 1991. Changes in water relations, carbohydrate contents and acid invertase activity associated with perianth elongation during anthesis of cut gladiolus flowers. Journal of the Japanese Society for Horticultural Science 60, 421–428.[Web of Science]
Yamamoto K, Komatsu Y, Yokoo Y, Furukawa T. 1994. Delaying flower opening of cut roses by cis-propenylphosphonic acid. Journal of the Japanese Society for Horticultural Science 63, 159–166.[Web of Science]
Yanovsky M, Kay S. 2001. Signaling networks in the plant circadian system. Current Opinion in Plant Biology 4, 429–435.[CrossRef][Web of Science][Medline]
Yanovsky MJ, Mazzella MA, Whitelam GC, Casal JJ. 2001. Resetting of the circadian clock by phytochromes and cryptochromes in Arabidopsis. Journal of Biological Rhythms 16, 523–530.
Zimmer R. 1962. Phasenverschiebung und andere Störlichtwirkungen auf die endogenen tagesperiodischen Blütenblattbewegungen von Kalanchoë blossfeldiana. Planta 58, 283–300.[CrossRef][Web of Science]
zur Lippe T. 1957. Wasseraufnahme und Blütenbewegung an Kalanchoë-infloreszenzen in verschiedenen Licht-Dunkelwechseln. Zeitschrift für Botanik 45, 43–55.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  T. S. Feild, D. S. Chatelet, and T. J. Brodribb Giant Flowers of Southern Magnolia Are Hydrated by the Xylem Plant Physiology, July 1, 2009; 150(3): 1587 - 1597. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Cawoy, J.-M. Kinet, and A.-L. Jacquemart Morphology of Nectaries and Biology of Nectar Production in the Distylous Species Fagopyrum esculentum Ann. Bot., November 1, 2008; 102(5): 675 - 684. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Ma, J. Xue, Y. Li, X. Liu, F. Dai, W. Jia, Y. Luo, and J. Gao Rh-PIP2;1, a Rose Aquaporin Gene, Is Involved in Ethylene-Regulated Petal Expansion Plant Physiology, October 1, 2008; 148(2): 894 - 907. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. K. Azad, T. Ishikawa, T. Ishikawa, Y. Sawa, and H. Shibata Intracellular energy depletion triggers programmed cell death during petal senescence in tulip J. Exp. Bot., May 31, 2008; (2008) ern066v1. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. I. PETER and S. D. JOHNSON Anther Cap Retention Prevents Self-pollination by Elaterid Beetles in the South African Orchid Eulophia foliosa Ann. Bot., March 1, 2006; 97(3): 345 - 355. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||