Journal of Experimental Botany, Vol. 51, No. 345, pp. 777-784,
April 2000
© 2000 Oxford University Press
Effects of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.)
Plant Environment Laboratory, Department of Agriculture, The University of Reading, Cutbush Lane, Shinfield, Reading RG2 9AD, UK
Received 20 October 1999; Accepted 21 December 1999
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Abstract |
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Groundnuts (Arachis hypogaea L.) are an important crop of the semi-arid tropics where they are often exposed to maximum temperatures of >40 °C for short periods during the growing season. The objectives of this study were to determine: (i) the effects of short periods of exposure to high temperature on flower production (FN), the proportion of flowers forming fruits (fruit-set) and the number of pegs and pods per plant (RNt); (ii) whether fruit-set is affected by high temperature during different periods of daylight in each diurnal cycle; and (iii) whether responses to temperature were qualitative or quantitative. Plants of cv. ICGV 86015 were grown in controlled environments at a day/night temperature of 28/22 °C from sowing until 9 d after flowering (DAF). Then, cohorts of plants were: (a) exposed to day temperature of 28, 34, 42 or 48 °C for 2, 4 or 6 d; or were (b) exposed to 34, 42 or 48 °C for 6 d either throughout a 12 h day (08.00 to 20.00 h, WD), or only during the first 6 h (AM) or second 6 h (PM) of the day. Values of RNt were significantly reduced by high temperature, by duration of exposure, and by timing of exposure. Variation in FN was quantitatively related to floral bud temperatures during the day over the range 28–43 °C. In contrast, only floral bud temperatures >36 °C during AM and WD significantly reduced fruit-set and hence RNt, whereas high PM temperature had no effect on fruit-set. These findings indicate that the response of RNt to day temperature is quantitative and can be modelled by combining the responses of FN and fruit-set to temperature.
Key words: Groundnut, flowering, fruit-set, heat stress, temperature.
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Introduction |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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High temperatures are a major constraint to crop adaptation and productivity, especially when these temperature extremes coincide with drought and with critical stages of plant development (McWilliam, 1980
). Groundnuts (Arachis hypogaea L.) are an important subsistence and cash crop of the semi-arid tropics where they are often exposed to maximum temperatures of >40 °C for short periods during the growing season (ICRISAT, 1994). Furthermore, with the present trends of global warming, temperatures are likely to become hotter, and an increase in mean air temperature of 2–3 °C is predicted to reduce groundnut yields in India by 23–36% (Hundal and Kaur, 1996). It is therefore important to investigate and quantify the effects of periods of high temperature on the reproductive yield of groundnut, both to improve our ability to simulate and predict responses to environment, and to help design screening methods for heat tolerance.
The optimum air temperature for growth and development of groundnut is between 25 °C and 30 °C (Williams and Boote, 1995). It has been shown, for example, that the numbers of pegs and pods were reduced by 33% by exposure to a day temperature of 35 °C compared with 30 °C (Ketring, 1984). The reproductive phase of groundnut is more sensitive to heat stress than the vegetative phase (Cox, 1979; Ketring, 1984). The greatest sensitivity to hot days (38 °C) occurs from 6 d before to 15 d after flowering (Vara Prasad et al., 1998, 1999a). In the latter experiment, the reduction in the number of fruits (i.e. pegs and pods) following exposure to a day temperature of 38 °C was primarily due to reduced fruit-set (the proportion of flowers producing pegs or pods), rather than to reduced flower production or to the proportion of pegs producing pods.
Studies on cowpea (Vigna unguiculata (L.) Walp; Hall, 1992) and common bean (Phaseolus vulgaris L.; Gross and Kigel, 1994) have shown that heat stress during floral bud development, specifically microsporogenesis, can reduce fruit-set due to damage to the pollen mother cells (Warrag and Hall, 1984), resulting in poor anther dehiscence, reduced pollen number and decline in pollen viability (Halterlein et al., 1980; De Beer, 1963). Fertilization may also be affected at anthesis by impaired style and ovule function (Gross and Kigel, 1994), failure of fertilization of pollen and ovule (Ormrod et al., 1967), and poor pollen tube growth (Talwar and Yanagihara, 1999). Post-fertilization fruit-set may be reduced by embryo abortion (Gross and Kigel, 1994).
Although periods of high temperatures (
35 °C) are known to reduce the number of fruits significantly, and therefore seed yields in groundnut, the sensitivity of flower production and fruit-set to temperature has not been quantified. The objectives of the present research were to determine: (i) the effects of short periods (2, 4 or 6 d) of exposure to high temperatures, i.e. 34 °C, 42 °C or 48 °C on flower production, fruit-set and the number of pegs and pods per plant; (ii) whether fruit-set in groundnut is relatively more or less sensitive to high temperatures during different periods of daylight in each diurnal cycle; and (iii) whether the responses of flower production, fruit-set and the numbers of pegs and pods per plant to temperature were quantitative or qualitative.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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Two experiments (Experiments 1 and 2) were conducted between June and August in 1997, and one experiment (Experiment 3) was conducted in 1999 in the controlled environment facilities of the Plant Environment Laboratory, Department of Agriculture, The University of Reading (51°27' N latitude and 00°56' W longitude). Experiments were undertaken in a polyethylene covered tunnel (poly-tunnel) maintained at a near optimum day/night temperature of 28/22 °C and in four modified Saxcil growth cabinets maintained at different day temperatures (Table 1
).
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The photo- and thermoperiod in both the poly-tunnel and each cabinet were coincident and equal at 12 h d-1. The photoperiod was controlled by a manually operated black-out facility in the poly-tunnel, and by automatic time switches in the cabinets. Air temperatures were measured in the poly-tunnel and the cabinets using screened and aspirated copper–constantan thermocouples positioned at the top of the plant canopy (30 cm above the soil surface). Readings were taken at 10 s intervals and means were stored for successive 10 min periods using a data logger (Delta-T Devices Ltd, Cambridge, UK). Carbon dioxide concentration in the cabinets was maintained at ambient concentration, 360 µmol CO2 mol-1 of air. Relative humidity during the day was maintained close to 70±5% in the poly-tunnel using water sprinklers and ventilation, while in the cabinets VPD was maintained at 1.2 kPa in all temperature regimes. The poly-tunnel transmitted 75% of incoming photosynthetically active radiation and photosynthetic photon flux density (PPFD) averaged 590 µmol m-2 s-1 during the experiment. The corresponding value of PPFD in each growth cabinet was 650 µmol m-2 s-1 obtained from a combination of cool white fluorescent tubes and incandescent lamps.
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Cultivar and plant husbandry |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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Uniform seeds of the Spanish botanical type (A. hypogaea subsp. fastigiata) cv. ICGV 86015 were selected and treated with Apron Combi 453 FS (Ciba, Agriculture, Cambridge, UK) as a precautionary measure against seed-borne diseases. Seeds were pregerminated on moist filter paper in Petri dishes kept in the dark for 2 d at 25 °C until radicles emerged. The germinated seeds were then sown, one per 2.5 l pot at a depth of 2.5 cm. The sides of the pots were covered with aluminium foil to reduce radiative heating. The rooting medium comprised sand, gravel, vermiculite, and loamless peat compost mixed in proportions of 4 : 2 : 2 : 1 (by vol), respectively. A commercial controlled-released fertilizer (0.15 kg kg-1 N, 0.10 kg kg-1 P, 0.12 kg kg-1 K, 0.02 kg kg-1 MgO plus trace elements; Osmocote Plus, Scotts UK Ltd., UK) was incorporated into the mixture at the manufacturer's recommended rate of 5 g l-1. Seeds were not inoculated with rhizobia and plants were dependent on inorganic nitrogen. All pots were soaked with tap water and allowed to drain for 24 h before sowing; thereafter they were irrigated as necessary through an automatic drip irrigation system in the poly-tunnels or were hand-watered during the 6 d period in the cabinets. There were no disease problems and sporadic pest infestations were controlled by releases of the predators Phytoseiulus persimilis Herriot against red spider mite (Tetranychus urticae Koch) and Amblyseius cucumeris Oudemes against thrips (Thrips tabaci Lindeman).
All experiments were sown initially with six replicates of each temperature treatment and with 12 replicates for the controls. Only uniform plants which flowered 28 d after sowing (DAS) were then selected for the experiments in order to ensure no effects of ‘escape’ and the rest were discarded, which gave four replicates of each temperature treatment and eight replicates of the controls. A subset of four plants from the control treatment were harvested at 18 d after flowering (DAF), to estimate the numbers of pegs and pods produced from those flowers which had opened before the imposition of the target treatments.
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Temperature treatments |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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During the period from sowing until 9 DAF, all plants were grown at a day/night air temperature of 28/22 °C in a poly-tunnel. Thereafter, cohorts of plants were transferred to different growth cabinets and exposed to various temperatures for a maximum of 6 d before being returned to the poly-tunnel maintained at air temperatures of 28/22 °C, where they remained until final harvest at 24 DAF (i.e. 52 DAS). Plants maintained at air temperatures of 28/22 °C in the cabinet for the entire 6 d treatment period served as controls for both experiments. Night-time air temperature in all the treatments was maintained at 22 °C.
Experiment 1. Duration of exposure to high temperature:
At 9 DAF, replicate plants were transferred to four different growth cabinets in which they were exposed to hot days of 34, 42 or 48 °C for 2, 4 or 6 d. In the 2 and 4 d duration treatments, plants were subsequently transferred to a cabinet maintained at an air temperature of 28 °C for the remainder of the 6 d period before being returned to the poly-tunnel.
Experiment 2. Timing of exposure to high temperature:
At 9 DAF, replicate plants were exposed to air temperatures of 34, 42 or 48 °C during either the first 6 h (08.00 to 14.00 h, AM) or for the second 6 h (14.00 to 20.00 h, PM) of the 12 h light period, or for the whole day (08.00 to 20.00 h, WD) for 6 d (i.e. 9–15 DAF). In the AM treatments plants were exposed to air temperatures of 34, 42 or 48 °C in different cabinets during the first 6 h of the light period and then transferred to an optimum air temperature (28 °C) cabinet for the second 6 h of the light period. In contrast, plants in the PM treatments plants were exposed to optimum air temperature (28 °C) during the first 6 h of the light period and then transferred to air temperatures of 34, 42 or 48 °C in different cabinets for the second 6 h of the light period.
Experiment 3. Comparison of ambient air temperature and floral bud temperature:
The plant husbandry and temperature treatments in this experiment were identical to those in Experiments 1 and 2. Floral bud and air temperatures were measured continuously over a 6 d period at mean air temperatures of 28, 34, 42, and 48 °C (Table 1
). Air temperature was measured with an aspirated shaded copper-constantan thermocouple placed at 30 cm above soil level. Floral bud temperature was measured in each of 4 buds per temperature treatment using 0.2 mm diameter copper-constantan thermocouples inserted into the buds when they were 5 mm long. Temperatures were measured at 10 s intervals and means were stored for successive 10 min periods using a datalogger (Delta-T Devices, Cambridge, UK).
Observations
Observations on the growth and development of plants were confined to Experiments 1 and 2. Duration (d) from sowing to the appearance of the first open flower and to the first peg 3 mm long were recorded on all plants. Thereafter, the numbers of flowers opening each day were counted until final harvest. Plants were harvested on two occasions; first at 9 d after the start of the temperature treatments (18 DAF) and then at final harvest at the start of fruit growth at 24 DAF. At both harvests the numbers of pegs and pods per plant were counted.
Data analysis
The fate of individual flowers (i.e. whether they produced a peg or a pod) was not monitored and so the total number of pegs and pods at the final harvest, hereafter referred to as the final reproductive number (RNf ), were produced from the flowers which had opened at 28 °C (i.e. in the poly-tunnel) plus those which had opened in the 6 d temperature treatments in the cabinets. In order to determine the fate of those flowers which opened during the 6 d temperature treatment it was assumed, based on previous experience, that for cv. ICGV 86015 the time from flower opening to peg appearance was 9 d. Observations on the duration from the appearance of floral buds 3 mm long to anthesis, and from anthesis to the formation of the peg at 28, 34, 42, and 48 °C showed no effect of temperature, mean durations being 3 d and 9±1 d, respectively. Therefore, all flowers that opened and were fertilized between the onset of flowering and 9 DAF should have produced a peg or a pod by the time the first harvest was taken at 18 DAF. The number of pegs and pods at this time was termed as the initial reproductive number (RNi). Similarly, any flower that opened between the end of the temperature treatments (15 DAF) and the final harvest 9 d later (24 DAF), should not have formed a peg. Therefore, the numbers of pegs and pods arising from those flowers that opened during the 6 d temperature treatment (the treatment reproductive number, RNt) were estimated as the difference between RNf and RNi. There was no significant difference among plants (P>0.50) in the number of flowers per plant produced before the start of the heat stress treatments at 9 DAF in Experiments 1 and 2. The number of pegs produced from flowers opening before 9 DAF (RNi), was 11±1.8 (SD).
Fruit-set during the temperature treatments was calculated as the ratio of RNt to the cumulative flower number opened during the 6 d temperature treatment (FN). The values of fruit-set were subject to angular transformation before analysis to ensure homogeneity of variance. Data on FN, fruit-set and RNt were analysed as a split-plot design with four replicates using Genstat 5 (Genstat 5 Committee, 1987).
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Results |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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Comparison of ambient air temperature and floral bud temperature
There were systematic and consistent differences between air and floral bud temperature at warmer mean temperatures in the growth cabinets (Table 1
; Fig. 1). At 28 °C there were no differences between air and floral bud temperature in the cabinets or in the poly-tunnel, but floral bud temperatures were about 1, 2 and 5 °C cooler than ambient air temperatures when exposed to day temperatures of 34, 42 and 48 °C, respectively. These differences were similar throughout the whole of the 6 d stress period and are illustrated by data for day 4 of the stress period in Fig. 1. Similar findings have been made reported in pea (Pisum sativum L.), where the floral bud temperature of plants grown in growth cabinets was 6 °C cooler than air temperature (although in the glasshouses and in the field air and floral bud temperatures were similar; Guilioni et al., 1997). Given these consistently different values the air temperatures in Experiments 1 and 2 were adjusted by -1.0, -1.9 and -4.9 °C in the 34, 42 and 48 °C temperature treatments, respectively, and the effects of heat stress have been expressed as floral bud temperature.
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Duration of exposure to high temperature
The values of FN, fruit-set and RNt were all significantly affected by day temperature, duration of exposure to temperature (P<0.001 for each) and their interaction (P<0.05 to P<0.01). Values of RNt were reduced by floral temperatures 40 °C and by 4 d or 6 d exposure to high temperature, with the relative decrease in RNt being greater when plants were exposed to a higher temperature for a longer period (Table 2).
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Day-time air temperature and duration of exposure to high temperature had similar effects on fruit-set (Table 3
), although it was only in the most extreme high temperature regimes, where a 6 d exposure to 40 °C and 4 d and 6 d exposures to 43 °C, significantly (P<0.001) reduced fruit-set to below the 28 °C value of 51.2%. Flower number was also affected in a similar negative manner by the temperature treatments and there was a strong and positive linear relation (r2=0.94, n=10; P<0.001) between RNt and FN (Fig. 2).
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Timing of exposure to high temperature
High temperature imposed for only the first 6 h (AM) or the second 6 h (PM) of the 12 h light period in each diurnal cycle had no significant (P>0.10) effect on FN (Fig. 3A). However, exposure to floral bud temperatures of 33, 40 and 43 °C for the WD significantly reduced FN when compared to plants maintained at a temperature of 28 °C. There was a strong and negative linear relation between FN and mean floral bud temperature during the day (r2=0.96, n=4; P<0.001) and FN decreased by 1.4 plant-1 °C-1.
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), or during the second 6 h (14.00–20.00 h; PM, 
) of the 12 h day. Vertical bars denote the SED for treatments.In contrast to FN, fruit-set was significantly affected by the timing of exposure to high temperature (Fig. 3B
). When plants were exposed to high temperatures during PM, temperature had no significant effect on fruit-set. However, when plants were exposed to high temperature during AM or for the WD, fruit-set was reduced from 51% at 28 °C to 0% when floral bud temperature was 43 °C. The effects of high temperature during AM or WD were similar (Fig. 3B) and fruit-set was decreased by about 3.2% plant-1 °C-1 between floral bud temperatures of 28 °C and 43 °C. Values of RNt were affected by the timing of exposure to high temperature (P<0.001) in a similar manner to that of fruit-set (Fig. 3C).
Relations between FN, fruit-set, RNt, and temperature
To examine the relation between FN and floral bud temperature during the whole day, and fruit-set and floral bud temperature during AM, data from both experiments have been combined in Fig. 4.
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, •), or exposed only during the first 6 h (08.00–14.00 h; AM, 
, 
, There was a strong and negative linear relation (r2=0.80, n=16; P<0.001) between FN and mean day (08.00 to 20.00 h) floral bud temperature (TWD) across all temperature treatments, whereby:
 | (1) |
). The greater values of FN for the AM and PM treatments in Fig. 3A for a given maximum floral bud temperature during the day were therefore clearly due to their cooler mean floral bud temperature during the day, since they were exposed to 6 h of air temperatures 34, 42 or 48 °C combined with 6 h of 28 °C.
Although FN was quantitatively related to mean floral bud temperature during the day, variation in fruit-set was most closely associated with variation in mean floral bud temperature during AM (Fig. 4B). When bud temperatures during the AM (TAM) were 
36 °C, temperature had no effect on fruit-set, which averaged 50.2±0.77%. However, when TAM exceeded the critical value of 36 °C, fruit-set was reduced to 0% at 43 °C (i.e. a reduction of 6.9% °C-1). The proportion of flowers producing pegs and pods (fruit-set) is therefore given by:
 | (2) |
 |
 |
). The sensitivity of RNt to floral bud temperature over the range of 28–43 °C was -1.4 plant-1 °C-1 and RNt reached zero at 42 °C. However, as RNt is the product of differential temperature effects on FN (Fig. 3A) and fruit-set (Fig. 3B), the response of RNt to temperature is better described by integrating Equations 1 and 2. Therefore, when TAM 36 °C, then RNt is determined by FN, whereby:
 | (3) |
 | (4) |
, where RNt is modelled by Equations 3 and 4, are shown by open and closed symbols, respectively.
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Discussion |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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Previous studies (Ong, 1984
) have shown for groundnut cv. Robut 33–1 that a mean diurnal air temperature regime of 36/25 °C imposed from sowing to maturity reduced the number of pods by 50% relative to those produced by plants grown at 27/17 °C. An air temperature regime of 35/22 °C (day/night) from flowering to maturity reduced fruit numbers by about 33% compared with values at 30/22 °C (Ketring, 1984). Similarly, it has been reported (Talwar et al., 1999) that pod number was reduced by 31% at 35/30 °C compared with 25/25 °C. In the present study a 6 d exposure to floral bud temperatures 33 °C also reduced RNt to a similar or greater extent, suggesting that it is this response to high temperature, even in plants given an opportunity to acclimate, which is the major determinant of pod number.
The effects of temperature on flower production, in contrast to fruit-set, were related to a simple quantitative response to mean day temperature, rather than AM or PM temperature, and no critical or threshold temperature was detected between 28 °C and 43 °C. Apparently, flower production is driven by the overall response to mean temperature, and with a similar optimum temperature of between 25 °C and 30 °C, to other developmental events such as leaf appearance or duration to flowering and podding (Leong and Ong, 1983). However, whether this reduction in flower production at high temperature is due to slower rates of floral bud initiation and floral bud development or, more likely, due to floral bud abortion (Talwar et al., 1999), is not known. Data presented earlier (Wood, 1968) also show a similar negative relation between FN and mean diurnal air temperature, and FN decreased by 2.6 plant-1 °C-1 over the range 23–34 °C. The night-time air temperatures used in earlier work (Wood, 1968) were 25 °C and 30 °C, compared with 22 °C in the present study, which may have contributed to the greater reduction in FN °C-1 (Vara Prasad et al., 1999b). Similar observations on FN were also made by Fortanier (Fortanier, 1957), who found that a hot day temperature of 35 °C relative to 29 °C reduced FN by about 50%. Clearly, groundnut plants can produce some flowers, though not necessarily fertile flowers, at extremely high temperatures.
This experiment has revealed that fruit-set is strongly influenced by timing of high temperature, and that it is the floral bud temperature during AM, rather than PM, that determines the response. Groundnut flowers typically open early in the morning, self-pollination occurs just before opening, and fertilization is completed within 5–6 h (Lim and Gumpil, 1984). Apparently, post-fertilization events, such as embryo formation which occurs>6 h after pollination, are not as sensitive to high temperature as pollination and fertilization and are not seriously affected by PM temperature (Fig. 3).
The critical or threshold daytime floral bud temperature for fruit-set was 36 °C, above which fruit-set was quantitatively reduced. Therefore, fruit-set exhibits a very different quantitative response to temperature compared to flower production. The appearance of leaves or the development of flowers from floral buds both require expansion growth and these events would appear to reflect the plants’ overall response to temperature, probably mediated through photosynthesis, respiration and growth (Williams and Boote, 1995). fruit-set, on the other hand, is the result of a series of specific anatomical and hormonal developmental events and it would appear that these developmental events do have a higher threshold temperature. There is some evidence in groundnut that high proline concentrations in the anthers and pollen, for example, contribute to tolerance to high temperature (Talwar and Yanagihara, 1999). Although the effect of temperature, particularly night temperature, on fruit-set has been studied in detail in a number of species, notably cowpea (Hall, 1992), common bean (Gross and Kigel, 1994) and tomato (Peet et al., 1998), in none of these studies has the response been quantified and a critical temperature identified.
In these experiments plants were exposed to high temperature for up to 6 d and therefore the effect of temperature on fruit-set could have resulted from effects during floral bud development (macro- and microsporogenesis), anthesis and fertilization, and embryo formation (Gross and Kigel, 1994). Although the precise stage of development most sensitive to high temperature has not yet been defined, other studies have shown that high temperature during micro- and macrosporogenesis and during fertilization in groundnut affects fruit-set. For example, Vara Prasad et al. (Vara Prasad et al., 1999a, b), using a reciprocal transfer experiment from optimum to high temperature and vice versa, demonstrated that fruit-set was reduced by high temperature during the 6 d before anthesis, i.e. during floral bud development. Similarly, reports of reduced pollen viability (De Beer, 1963; Vara Prasad et al., 1999b) and pollen number (Vara Prasad et al., 1999b) at day temperatures>33 °C are indicative of effects of high temperature during micro-and macrosporogenesis. Talwar and Yanagihara (Talwar and Yanagihara, 1999) have also shown that day/night air temperatures of 35/25 °C increased the length of the hypanthium and reduced the rate of pollen tube growth in heat-susceptible (but not heat-tolerant) genotypes of groundnut when compared to 25/20 °C, both factors which would reduce the chances of successful fertilization.
Under field conditions it is unlikely that a mean temperature of 36 °C for 6 h during the morning would be experienced very often, at least under well-watered conditions. However, short episodes of high (>35 °C) temperature during the day do occur frequently in the semi-arid tropics (ICRISAT, 1994). Further research is needed to determine the effect of high temperature for periods shorter than 6 h, and whether the timing of high temperature within the 6 h period also influences fruit-set through differential effects on the processes involved as described above. However, irrespective of the caveat about the frequency of occurrence of the critical temperature for fruit-set, flower production and, therefore, fruit number will be reduced when mean day temperature is>28 °C, and such values are commonly encountered in the semi-arid tropics (Sivakumar et al., 1993).
In summary, this research has shown that only 6 d exposure to day temperature 33 °C at 9 DAF significantly reduced flower production, fruit-set and fruit number. Variation in flower number was quantitatively related to mean floral bud temperature during the day over the range 28–43 °C. In contrast, variation in fruit-set was related to floral bud temperature during the first 6 h of the light period above a critical value of 36 °C. The response of fruit number to temperature can be modelled by combining the quantitative responses of flower number and fruit-set to temperature.
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Acknowledgments |
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We thank the Felix Foundation and the Department of Agriculture of The University of Reading for financial support, and Messers KE Chivers, SD Gill and Mrs C Hadley for technical assistance. We also thank Dr Qi Aiming for his comments on the manuscript and the ICRISAT Asia Centre, Hyderabad, India for supplying seed.
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Notes |
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1 To whom correspondence should be addressed. Fax: +44 118 988 5491. E-mail: p.q.craufurd{at}reading.ac.uk
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References |
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TopAbstractIntroductionMaterials and methodsCultivar and plant husbandryTemperature treatmentsResultsDiscussionReferences |
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S. V. K. Jagadish, P. Q. Craufurd, and T. R. Wheeler Phenotyping Parents of Mapping Populations of Rice for Heat Tolerance during Anthesis Crop Sci., May 1, 2008; 48(3): 1140 - 1146. [Abstract] [Full Text] [PDF]
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R. A. Betts Integrated approaches to climate-crop modelling: needs and challenges Phil Trans R Soc B, November 29, 2005; 360(1463): 2049 - 2065. [Abstract] [Full Text] [PDF]
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S. Sato, M. M. Peet, and J. F. Thomas Determining critical pre- and post-anthesis periods and physiological processes in Lycopersicon esculentum Mill. exposed to moderately elevated temperatures J. Exp. Bot., May 1, 2002; 53(371): 1187 - 1195. [Abstract] [Full Text] [PDF]
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P. Q. Craufurd, P. V. V. Prasad, and R. J. Summerfield Dry Matter Production and Rate of Change of Harvest Index at High Temperature in Peanut Crop Sci., January 1, 2002; 42(1): 146 - 151. [Abstract] [Full Text] [PDF]
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