Journal of Experimental Botany, Vol. 53, No. 371, pp. 1089-1098,
May 2002
© 2002 Oxford University Press
Original Papers |
A comparison of the effects of IAA and 4-Cl-IAA on growth, proton secretion and membrane potential in maize coleoptile segments
University of Silesia, Faculty of Biology, Department of Plant Physiology, ul. Jagiellonska 28, PL-40032 Katowice, Poland
Received 31 March 2001; Accepted 21 December 2001
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Abstract |
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The physiological activity of exogenous 4-Cl-IAA, as compared to IAA, was examined in maize coleoptile segments. It was found that in this model system 4-Cl-IAA is much more active in the stimulation of elongation than IAA. Simultaneous measurements of growth and external pH indicated that administration of either IAA or 4-Cl-IAA resulted in medium acidification. The kinetics of the pH changes, however, were faster after the addition of 4-Cl-IAA. In contrast to IAA, the coleoptile segments treated with chlorinated auxin were not able to increase medium pH after its initial drop. The re-addition of IAA after 5 h further enhanced growth over the next 2 h by 31%. By contrast, the re-addition of 4-Cl-IAA at the same time protocol as IAA did not cause an additional effect. The administration of 10 µM IAA induced in maize coleoptile cells a transient depolarization followed by a slow hyperpolarization of their membrane potential. In contrast to IAA, 4-Cl-IAA at 1 µM caused an immediate hyperpolarization of the membrane potential which, on average, was 2-fold greater than for IAA. The results reported here provide further evidence that 4-Cl-IAA is much more active, as compared to IAA, in stimulating the growth of maize coleoptile segments. Although it has not been directly demonstrated here, a plausible interpretation for the high 4-Cl-IAA activity is that, at least in part, it might be caused via a reduced metabolism of 4-Cl-IAA. Furthermore, for the first time, the data show that membrane potential responds to 4-Cl-IAA in a qualitatively different fashion than to IAA. These findings may, in turn, suggest a specific signal transduction pathway to 4-Cl-IAA in maize coleoptile cells.
Key words: Auxin, coleoptile segments, growth, membrane potential, proton secretion.
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Introduction |
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It is now generally agreed that indole-3-acetic acid (IAA) is the major and most abundant auxin in plants. IAA plays a key role in the regulation of plant growth and development (Moore, 1989; Davies, 1995). Over the last few years significant progress has been made in understanding the IAA-induced signal transduction pathway (Venis and Napier, 1991; Napier and Venis, 1995; Venis et al., 1996; Macdonald, 1997; Lüthen et al., 1999). Although other auxins, such as 4-chloroindole-3-acetic acid (4-Cl-IAA), indole-3-butyric acid (IBA) and phenylacetic acid (PAA) have also been identified in plants (reviewed by Normanly et al., 1995; Normanly, 1997), little is known about their physiological function.
4-Cl-IAA occurs naturally in a number of plants, mainly members of the Fabaceae (Engvild, 1975, 1980; Engvild et al., 1978, 1980; Hofinger and Böttger, 1979; Katayama et al., 1987), but it has also been found in pine seeds (Ernstsen and Sandberg, 1986).
Since the discovery of 4-chloroindoleacetic acid in immature seeds of Pisum sativum in 1967 (Gandar and Nitsch, 1967; Marumo et al., 1968), much evidence for its high biological activity has been reported. In early experiments Böttger et al. found that 4-Cl-IAA was much more active, as compared to IAA, both for straight growth of the Avena coleoptile segments and for proton extrusion in stem protoplast suspensions of Helianthus annuus L. and Pisum sativum L. (Böttger et al., 1978). Somewhat later, other authors in various bioassays found a similar high hormonal activity of 4-Cl-IAA (Pless et al., 1984; Ahmad et al., 1987; Hatano et al., 1987). It is noteworthy that some other mono- and dihalogenated auxins (e.g. 5-,6-Cl-IAA, 5,6-Cl2-IAA) demonstrate very strong auxin activity (Böttger et al., 1978; Barr et al., 1991; Reinecke et al., 1995), whereas 5,7-Cl2-IAA is one of the strongest anti-auxins known (Böttger et al., 1978; Hatano et al., 1987; Lüthen and Böttger, 1988).
In the last ten years there was a renewed emphasis on studying the effects caused by 4-Cl-IAA, largely as a result of intriguing and conflicting observations. For example, it has been suggested that chloroindole auxins of pea, a plant in which they occur naturally, may be hypothetical death hormones or senescence factors (Engvild, 1989, 1996). On the other hand, it was shown that in maize, which does not contain chlorinated auxins naturally (Hofinger and Böttger, 1979), 4-Cl-IAA is much more active compared with IAA (Fischer et al., 1992; Karcz and Burdach, 1995; Karcz et al., 1999). In turn, others showed that the 4-Cl-IAA-induced growth of the maize coleoptile segments was 10 times higher than that of 1-NAA (1-naphthylacetic acid) whereas the binding affinities of 4-Cl-IAA to auxin binding site I (ABP 1) and site II were 100 times lower compared with 1-NAA (Hertel, 1994, 1995; Stotz and Hertel, 1994). This 1000-fold discrepancy between biological activity and binding activity of both auxins was used by these authors as an argument that auxin binding site I and site II are not the true auxin receptors (but see also Venis, 1995). Soon after, however, in experiments performed with maize coleoptile segments, a clear correlation was found between the growth-promoting effect of 4-Cl-IAA and its binding affinity to ABP 1 (Rescher et al., 1996). In the past few years, a function of 4-Cl-IAA in pea pericarp growth and gibberellin metabolism has been proposed (Ozga et al., 1993; Ozga and Brenner, 1992; Huizen et al., 1995). This idea has been further used in the assumption that 4-Cl-IAA's strong auxin activity in pea occurs via a receptor and signal transduction pathway unique to 4-Cl-IAA (Reinecke et al., 1999).
In spite of the large number of recent papers published on 4-Cl-IAA activity (for review see Reinecke, 1999; Reinecke et al., 1999) little is known about the mechanism of its high biological activity in grass coleoptiles.
The main objective of the present study was the comparison of IAA and 4-Cl-IAA-induced growth, proton secretion and membrane potential in maize coleoptile segments. As far as is known, 4-Cl-IAA has never been examined for its ability to regulate electrogenic activity of the cell. To address this problem an effect of 4-Cl-IAA on membrane potential and proton secretion in maize coleoptile cells was studied.
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Materials and methods |
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Plant material
Seeds of maize (Zea mays L.) cv. K33xF2 were soaked in tap water, sown on wet wood wool in plastic boxes and placed in a growth chamber. The experiments were carried out with 10 mm long segments obtained from 4-d-old maize coleoptiles grown in the dark at 27±1 °C. The coleoptile segments with the first leaves removed were excised 3 mm below the tip and collected in water.
Chemicals
Aqueous stock solution (1 mM) was prepared from indole-3-acetic acid (Serva, Heidelberg, Germany). 4-Chloroindole-3-acetic acid (Sigma, St Louis, USA) was dissolved in isopropanol. The final concentration of isopropanol in the incubation medium did not exceed 0.1%, which was shown to be without any effect on the growth rates (Claussen et al., 1997).
Growth measurements
The growth experiments were carried out in two, independent, elongation-measuring systems. In the first, high resolution measurements of growth rate were performed with an angular position transducer (TWK Electronic, Düsseldorf, Germany), which resulted in a precise record of the growth kinetics. In this system six unabraded coleoptile segments, 10 mm in length, were strung on a stainless steel needle and inserted vertically in an intensively aerated solution (30 ml) of the following composition: 1 mM KCl, 0.1 mM NaCl, 0.1 mM CaCl2; initial pH 5.8–6.0. The length of coleoptile segments was sampled every 3 min by a CX 721 converter (Elmetron, Poland). The data stored on the diskette were analysed with ‘Statistica’ program (version 5.1 ‘87’ licence-SP711660411NET5). The growth rate was expressed in µm s-1 cm-1. A similar procedure for measuring the rate of elongation growth of maize coleoptile segments was previously described (Lüthen and Böttger, 1992, 1993).
In the second system the apparatus for simultaneous measurements of elongation growth and pH of the incubation medium was used, as previously described (Karcz et al., 1990). Briefly, the optical system used for growth measurements (shadow graph method) permitted recording of the longitudinal extension of a stack of 21 segments. The volume of the incubation medium (solution with the same composition as that used in the first system) in the elongation and pH-measuring apparatus was 6.3 ml (0.3 ml segment-1). In this apparatus the incubation medium also flowed through the lumen of the coleoptile cylinders (Karcz et al., 1995). This feature permits the treatment solutions to be in direct contact with the interior of the segments, which significantly enhanced both the elongation growth of the coleoptile segments and proton secretion (Karcz et al., 1995). This experimental set-up enabled coleoptile abrasion to be avoided (Dreyer et al., 1981) that inhibits (c. 30%) elongation growth (Kutschera and Schopfer, 1985a; Lüthen et al., 1990; Karcz et al., 1995). A similar procedure for measuring elongation (but without the access of growth substances to the lumen of coleoptile segments) was used earlier (Kutschera and Schopfer, 1985a). All manipulations and growth experiments were conducted under dim green light. The temperature of all solutions in the elongation-measuring systems was termostatically controlled at the level of 25±0.5 °C.
Measurements of pH
As mentioned above, pH changes of the incubation medium were measured simultaneously with growth using the same tissue sample. Measurements of pH were performed with the pH-meter (type N-517, Mera-Elwro, Poland) and pH electrode OSH 10-10 (Metron, Poland). Growth and pH were read every 15 min under the same conditions.
Electrophysiology
All electrophysiological experiments were performed on intact, 10 mm long, coleoptile segments. The standard electrophysiological technique was used for membrane potential measurements, as previously described (Stolarek and Karcz, 1987; Karcz and Stolarek, 1988). The membrane potential (Em) was measured by recording the voltage between a 3 M KCl-filled glass micropipette inserted into the parenchymal cells and a reference electrode in the bathing medium containing the same composition as used in growth experiments (e.g. 1 mM KCl, 0.1 mM NaCl, 0.1 mM CaCl2; initial pH 5.8–6.0). Before electrophysiological experiments the coleoptile segments were preincubated within 2 h in an intensively aerated bathing medium. After preincubation the segments were transferred into a perfusion Plexiglass chamber, which was mounted on a microscope stage. The microelectrodes were inserted into the cells under the microscope by means of micromanipulator (Hugo Sachs Elektronik, Germany). Medium flow was driven by a peristaltic pump (type PP 1B-05A, Zalimp, Poland), which also allowed a change to the bathing medium in the chamber (usually 4-fold within less than 2 min). Micropipettes were pulled on a vertical pipette puller (model L/M-3P-A, List-Medical, Germany) from borosilicate glass capillaries (type 1B150F-3, World Precision Instruments, USA). Tip diameters were less than 1 µm.
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Results |
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Effect of 4-Cl-IAA and IAA on growth rate
Figure 1
shows the growth-promoting activity of 1 µM 4-Cl-IAA and 10 µM IAA in unabraded maize coleoptile segments. The segments were first preincubated (over 2 h) in auxin-free medium until a low, constant growth rate (between 0.01–0.03 µm s-1 cm-1) was achieved, whereupon 4-Cl-IAA or IAA was added. As can be seen in Fig. 1 both auxins induced rapid growth, but the chlorinated auxin had a higher growth-promoting efficiency compared with IAA. For example, the maximal growth rate in 4-Cl-IAA was 0.310±0.034 µm s-1 cm-1 (mean±SD, n=8) while the rate of only 0.185±0.028 µm s-1 cm-1(mean±SD, n=11) was observed in IAA. The maximal growth rate for both auxins was reached at a similar time and was usually stable for 4-Cl-IAA after 5 h of incubation. By contrast, IAA-induced growth decreased gradually after this time to a growth rate similar to that in the control medium (data not shown). The growth rate in the control (endogenous growth) did not exceed 0.07 µm s-1 cm-1. The total 4-Cl-IAA and IAA-induced elongation growth of maize coleoptile segments after 10 h (calculated as the sum of extension from 3 min interval measurements) was 4.5- and 3.5-fold greater than in the control (1405±383.2 µm cm-1; mean±SD, n=8), respectively (inset on the right side, Fig. 1).
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Effect of 4-Cl-IAA and IAA on elongation growth and simultaneously measured pH changes of the incubation medium
The experiments described in this section were performed using the growth and pH-measuring apparatus in which unabraded coleoptile segments (21 segments per 6.3 ml), with access of incubation medium to their lumen, were incubated in unbuffered, intensively aerated medium. Using this apparatus, measurements were carried out in which both auxins were added to the medium after 2 h of preincubation or at the steady-state level of pH (at acid equilibrium according to the definition proposed for this value pH by Peters and Felle, 1991a). When IAA or 4-Cl-IAA was applied according to the first variant of experiments (after 2 h of preincubation), chlorinated auxin, which would be expected taking into account the growth rate data (Fig. 1
), was much more active in stimulation of elongation than IAA (Fig. 2). In the presence of 4-Cl-IAA and IAA the elongation growth of maize coleoptile segments was 2.6- and 2.0-fold higher than in the control (1444.7±128.6 µm cm-1, mean±SD, n=11), respectively. Figure 3 shows a comparison of the effects of both auxins (added after 2 h preincubation) and the control treatment on medium pH. For comparison, the effect of 1 µM fusiccocin (FC) on medium pH has also been shown. This substance is much more effective in the stimulation of H+ extrusion than IAA (for review see Marré, 1979). The data in Fig. 3 indicate that coleoptile segments, incubated in auxin-free medium (control) characteristically change the pH of their medium; usually within the first 2 h an increase of pH to the level near neutral is observed, followed by a slow decrease of pH to a steady-state level at 5.2. When IAA or 4-Cl-IAA was added (after 2 h of preincubation) to auxin-free medium, an additional decrease, as compared to the control medium, was observed. The rate of acidification, however, was higher in 4-Cl-IAA. A minimum value at pH 5 was reached in response to both treatments. For IAA, approximately 5–6 h after its addition to the incubation medium, recovery of pH (a net uptake of protons) to the control treatments was observed. No pH recovery, however, was detected after treatment with 4-Cl-IAA.
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In the second set of experiments (performed at the steady-state level of pH) IAA or 4-Cl-IAA was applied no earlier than 9 h after the start of the experiments (for selection this time see the control in Fig. 3
). Administration of IAA and 4-Cl-IAA after this time enhanced, over the next 6 h, the elongation growth of coleoptile segments 2.4- and 4.2-fold, as compared to the control, respectively (Fig. 4A). Both auxins applied at acid equilibrium evoked additional acidification of the medium, significantly faster and greater after the addition of 4-Cl-IAA than IAA (Fig. 4B, C). Similar to the first set of experiments, coleoptile segments treated with 4-Cl-IAA were not able to increase medium pH after its initial drop (Fig. 4C).
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The effect of 4-Cl-IAA and IAA on the membrane potential (Em)
After insertion of the microelectrode into the cell and stabilization of Em (<10 min) the bathing medium (auxin-free medium) was changed for a new one, at the same salt composition, containing additionally IAA or 4-Cl-IAA at a final concentration 10 µM and 1 µM, respectively. The Em of the parenchymal cells, before being changed in response to the auxins, was -114.8±5.9 mV (mean±SD, n=20). The addition of IAA to the incubation medium (Fig. 5) caused a transient depolarization of Em by 7.6±3.7 mV (mean±SD, n=9) followed by a delayed hyperpolarization, during which the membrane potential became 12±6.3 mV (mean±SD, n=9) more negative than the original potential. The hyperpolarization induced by IAA reached steady-state after 30–35 min. By contrast, 1 µM 4-Cl-IAA caused a rapid hyperpolarization of 24±10.6 mV (mean±SD, n=11), after a lag phase of 1 min or less, without an initial depolarization of the Em. The rate of hyperpolarization induced by chlorinated auxin was much higher, as compared to IAA.
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Re-addition of auxins to the IAA and 4-Cl-IAA-treated sample
Because of the possibility that breakdown of IAA is responsible for its low efficiency in the stimulation of elongation, as compared to 4-Cl-IAA, the variant in which the auxins were re-added after 5 h to the IAA or 4-Cl-IAA-sample was tested (IAA or 4-Cl-IAA-sample means that either IAA or 4-Cl-IAA was added only once after 2 h of preincubation) and the growth was measured over the next 2 h. This possibility would be especially true for experiments performed with the growth and pH-measuring apparatus, in which the volume of incubation medium per segment was very low (0.3 ml segment-1). Figure 6 shows the elongation for the coleoptile segments measured within 2 h (between 5 and 7 h) in medium to which either IAA or 4-Cl-IAA was re-added. The data indicate that the re-addition of IAA to the IAA-sample additionally enhanced elongation growth by 31% over the next 2 h, which was still 31% less than that for the 4-Cl-IAA-sample. By contrast, 4-Cl-IAA re-added at the same time protocol as IAA did not cause an additional effect. Interestingly, the addition of 4-Cl-IAA after 5 h to the IAA-sample enhanced growth over next 2 h by 67%, whereas addition of IAA to the 4-Cl-IAA-sample only caused a slight effect (Fig. 6).
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Discussion |
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The data presented in this paper show that indole-3-acetic acid (IAA), as the principal regulator of plant elongation growth, causes (1) acceleration of elongation growth as compared to endogenous growth (Figs 1
, 2, 4A), (2) enhancement of proton extrusion as compared to auxin-free medium (Figs 3, 4B), and (3) transient depolarization followed by a slow hyperpolarization of membrane potential (Fig. 5).
The IAA-induced growth in maize coleoptile segments observed here is qualitatively in good agreement with the results obtained by other authors (Kutschera and Schopfer, 1985a, b; Lüthen et al., 1990; Claussen et al., 1996; Karcz et al., 1990, 1999). Because of different experimental conditions (e.g. number of coleoptiles per medium volume, composition of the incubation medium, concentration of the effectors, initial pH of the medium etc.) direct quantitative comparison of these data with the results presented by other authors is difficult. Also, in this elongation and pH-measuring system (second system), in which the volume of the medium per segment was very low (0.3 ml segment-1), both 4-Cl-IAA and IAA-induced elongation significantly differ as compared to growth measured in the growth rate-measuring system (first system) with 5 ml of medium per segment. The endogenous growth of maize coleoptile segments (control in Fig. 1), measured by means of the transducers, consisted of three typical phases; two phases of endogenous growth acceleration separated by a low steady growth rate (Cline et al., 1974; Evans and Schmitt, 1975; Bergfeld et al., 1987; Bleiss and Ehwald, 1993; Peters et al., 1998). The first phase, lasting in these experiments c. 70 min, was usually observed 15–20 min after excision. The second phase of accelerated growth appeared to start 110–130 min after excision and lasted for several hours; it is commonly described as the spontaneous growth response (SGR). In these experiments SGR remained steady for at least 5 h after it was initiated. The data on endogenous growth are in good agreement with the data obtained previously (Peters et al., 1998) in experiments performed with unabraded maize coleoptile segments growing in the solution at the same composition as used here. Chlorinated auxin (4-Cl-IAA) added to the incubation medium (either after 2 h of preincubation or at the acid equilibrium), at a final concentration of 1 µM, brought about a strong increase in growth, as compared to IAA (Figs 1, 2, 4A). This concentration, as has previously been shown (Karcz et al., 1996, 1999; Rescher et al., 1996) was optimal (taking into account the bell-shaped dose–response curve for 4-Cl-IAA) for the growth of maize coleoptile segments. Comparing data for both auxins (Figs 1, 2, 4A), it is evident that 4-Cl-IAA is much more effective in growth stimulation than IAA. The second important indication is that growth rate for 4-Cl-IAA is stable after c. 450 min (Fig. 1), whereas for IAA, after reaching a maximal value, it gradually decreased to the growth rate in the control (data not shown). As previously suggested (Karcz et al., 1999), and also quantitatively shown in the present experiments with the re-addition of auxins (Fig. 6), the breakdown of IAA is the main (but not the only) reason for its low efficiency in growth stimulation, as compared to 4-Cl-IAA. Re-addition of IAA after 5 h to the IAA-sample additionally enhanced, over the next 2 h, IAA-induced growth by 31%, which was still 31% and 36% less than the elongation growth in the 4-Cl-IAA-sample and the 4-Cl-IAA-induced growth in the IAA-sample, respectively. 4-Cl-IAA re-added at the same time protocol as IAA to 4-Cl-IAA-sample did not cause an additional effect.
The second feature of auxin action on grass coleoptile segments is the acidification of the incubation medium. This phenomenon is the base of the ‘acid-growth theory’ of auxin action, proposed earlier (Rayle and Cleland, 1970; Hager et al., 1971). In spite of abundant literature on auxin action the validity of the acid-growth theory has been a subject of controversy (Rayle and Cleland, 1992; Schopfer, 1993; Kutschera, 1994).
Unabraded maize coleoptile segments, but with the access of the incubation medium to their lumen, characteristically changed the external medium pH. This characteristic change of the external pH consisted of an initial increase of pH, that usually ended within 2 h at a pH near neutral, and a slow pH decrease to the stable level at 5.2. It has recently been suggested that medium pH measurements, lacking such characteristic values of pH changes, are indicative of poor experimental conditions (Peters et al., 1998). It is noteworthy that the characteristic pattern of medium pH changes was observed with abraded and unabraded segments (Peters and Felle, 1991a). Addition of IAA or 4-Cl-IAA to the control medium (after 2 h of preincubation) caused an additional drop of the external medium pH, significantly sooner for 4-Cl-IAA than for IAA. An acidic minimum at pH 5 was reached for both auxins, but somewhat faster for 4-Cl-IAA than IAA. For IAA, approximately 5–6 h after its addition to the incubation medium, the recovery of pH (a net uptake of protons) to the control treatments was observed. An equilibrium between the secretion of protons and their uptake (steady-state level of pH) observed for 4-Cl-IAA after 5 h match strikingly in time with the stable value of growth rate (Fig. 1). In the case of IAA, however, the recovery of the external medium pH correlates in time with the decrease of growth rate (Figs 1, 3). However, when both auxins were added to the control medium at the steady-state level of pH their effect on medium pH was much more expressive (Fig. 4B, C). 4-Cl-IAA was not only faster, but also acidified the external medium much more, as compared to IAA. In such conditions, the coleoptile segments treated with 4-Cl-IAA, were also not able to increase medium pH after its initial drop (Fig. 4C). The net proton uptake in the presence of IAA (recovery of medium pH) has previously been observed with maize coleoptile segments by others (Jacobs et al., 1984; Kutschera and Schopfer, 1985a, b; Peters and Felle, 1991a, b) and as shown earlier (Peters et al., 1997) this effect is due to rapid IAA metabolism. In the literature there is a lack of data showing the effect of 4-Cl-IAA on medium pH simultaneously measured with growth.
The third, characteristic, feature of auxin action on grass coleoptile cells is a transient depolarization followed by a slow hyperpolarization of their membrane potential (Cleland et al., 1977; Bates and Goldsmith, 1983; Felle et al., 1986, 1991; Senn and Goldsmith, 1988; Peters et al., 1992; Keller and Volkenburgh, 1996). There is no doubt that the slow plasma membrane hyperpolarization is a consequence of a stimulated proton extrusion through the H+-ATPase (Lohse and Hedrich, 1992; Rücke et al., 1993; Hedrich et al., 1995). For IAA-induced initial membrane depolarization, however, several mechanisms including activation of anion channels (Marten et al., 1991; Keller and Volkenburgh, 1996), activation of nH+/IAA--symporter (Felle et al., 1991) or unspecific weak acid effects (Bates and Goldsmith, 1983), are proposed. In these experiments application of IAA, at a final concentration of 10 µM induced the typical biphasic kinetics of the membrane potential changes (Fig. 5). The value of depolarization, the time within which depolarization was reached and the membrane potential measured after 35 min in IAA were not significantly different from the results obtained with maize or oat by other authors (indicated above). By contrast to IAA, 4-Cl-IAA added at a final concentration of 1 µM caused an immediate hyperpolarization of the membrane potential, which started after a lag of 1 min or less and which was on average 2-fold greater at 35 min than for IAA. As far as is known 4-Cl-IAA has never been studied electrophysiologically. 4-Cl-IAA-induced hyperpolarization and proton extrusion (Figs 5, 3) correlate strikingly in time, possibly both resulting from an activation of the plasma-membrane H+-ATPase. Similarity of the initial kinetics (at least within first 40 min) for both FC and 4-Cl-IAA-induced proton extrusion and a rapid hyperpolarization of the membrane potential in the presence of chlorinated auxin and FC (data not shown) support the suggestion that 4-Cl-IAA activates H+-ATPase.
In conclusion, the results presented in this paper demonstrate that 4-Cl-IAA is much more effective than IAA in stimulating the growth reaction of maize coleoptile segments. A plausible interpretation for the high 4-Cl-IAA's activity is that it, at least in part, might be caused via a reduced metabolism of 4-Cl-IAA. This suggestion is supported by three lines of evidence: (1) steady-state growth rate and medium pH after 450 min treatment with 4-Cl-IAA (not the case for IAA, Fig. 1); (2) recovery of the medium pH drop for IAA, but not for 4-Cl-IAA (Figs 3, 4B, C); (3) re-addition of both auxins to IAA or 4-Cl-IAA-sample (additional effect for IAA, but not for 4-Cl-IAA, Fig. 6). In turn, the qualitative differences between IAA and 4-Cl-IAA-induced changes in membrane potential may suggest a specific signal transduction pathway to 4-Cl-IAA in maize coleoptile segments.
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Acknowledgements |
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We wish to thank Dr Alexander Grabov (Imperial College at Wye, UK) for critical reading of this manuscript and correcting the English text.
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Footnotes |
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1 To whom correspondence should be addressed. E-mail: karcz{at}us.edu.pl
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References |
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Ahmad A, Anderson AS, Engvild KC. 1987. Rooting, growth and ethylene evolution of pea cuttings in response to chloroindole auxins. Physiologia Plantarum 69, 137–140.
Barr R, Böttger M, Crane FL. 1991. The effect of chloro-derivatives of indole acetic acid on plasma membrane electron transport and proton excretion. Proceedings of the Indiana Academy of Science 99, 129–136.
Bates GW, Goldsmith MHM. 1983. Rapid response of the plasma-membrane potential in oat coleoptiles to auxin and other weak acids. Planta 159, 231–237.
Bergfeld R, Speth V, Schopfer P. 1987. Reorientation of microfibrils and microtubules at the outer epidermal wall of maize coleoptiles during auxin-mediated growth. Botanica Acta 101, 31–41.
Bleiss W, Ehwald R. 1993. Transient changes in length and growth of wheat coleoptile segments following treatments with osmotica and auxin. Physiologia Plantarum 88, 541–548.
Böttger M, Engvild KC, Soll H. 1978. Growth of Avena coleoptiles and pH drop of protoplast suspensions induced by chlorinated indoleacetic acids. Planta 140, 89–92.
Claussen M, Lüthen H, Blatt M, Böttger M. 1997. Auxin-induced growth and its linkage to potassium channels. Planta 201, 227–234.
Claussen M, Lüthen H, Böttger M. 1996. Inside or outside? Localization of the receptor relevant to auxin-induced growth. Physiologia Plantarum 98, 861–867.
Cleland RE, Prins HBA, Harper JR, Higinbotham N. 1977. Rapid hormone-induced hyperpolarization of the oat coleoptile transmembrane potential. Plant Physiology 59, 395–397.
Cline MG, Edgerton M, Rehm MM. 1974. Accelerated endogenous growth in Avena coleoptile segments. Planta 120, 213–214.
Davies PJ. 1995. Plant hormones physiology, biochemistry and molecular biology, 2nd edn. Dordrecht: Kluwer Academic Publishers, 1–12.
Dreyer SA, Seymour V, Cleland RE. 1981. Low conductance of plant cuticles and its relevance for the acid-growth theory. Plant Physiology 68, 664–666.
Engvild KC. 1975. Natural chlorinated auxins labelled with radioactive chloride in immature seeds. Physiologia Plantarum 34, 286–287.
Engvild KC. 1980. Simple identification of the neutral chlorinated auxin in pea by thin layer chromatography. Physiologia Plantarum 48, 435–437.
Engvild KC. 1989. The death hormone hypothesis. Physiologia Plantarum 77, 282–285.
Engvild KC. 1996. Herbicidal activity of 4-chloroindoleacetic acid and other auxins on pea, barley and mustard. Physiologia Plantarum 96, 333–337.
Engvild KC, Egsgaard H, Larsen E. 1978. Gas chromatographic-mass spectrometric identification of 4-chloroindolyl-3-acetic acid methyl ester in immature green peas. Physiologia Plantarum 42, 365–368.
Engvild KC, Egsgaard H, Larsen E. 1980. Determination of 4-chloroindole-3-acetic acid methyl ester in Lathyrus, Vicia and Pisum by gas chromatography-mass spectrometry. Physiologia Plantarum 48, 499–503.
Ernstsen A, Sandberg G. 1986. Identification of 4-chloroindole-3-acetic acid and indole-3-aldehyde in seeds of Pinus sylvestris. Physiologia Plantarum 68, 511–518.
Evans ML, Schmitt MR. 1975. The nature of spontaneous changes in growth rate in isolated coleoptile segments. Plant Physiology 55, 757–762.
Felle H, Brummer B, Bertl A, Parish RW. 1986. Indole-3-acetic acid and fusicoccin cause cytosolic acidification of corn coleoptile cells. Proceedings of the National Academy of Sciences, USA 83, 8892–8895.
Felle HH, Peters WS, Palme K. 1991. The electrical response of maize to auxins. Biochimica at Biophysica Acta 1064, 199–204.[Medline]
Fischer C, Lüthen H, Böttger M, Hertel R. 1992. Initial transient growth inhibition in maize coleoptiles following auxin application. Journal of Plant Physiology 141, 88–92.
Gandar JC, Nitsch C. 1967. Isolement de l ‘ester methylique d ‘un acide chloro-3-indolylacetiqe a partir de graines immatures de pois Pisum sativum L. CR Academie de Science (Paris) Serie D 265, 1795–1798.
Hager A, Menzel H, Krauss A. 1971. Versuche und Hypothese zur Primärwirkung des Auxins beim Streckungswachstum. Planta 100, 1–15.
Hatano T, Katayama M, Marumo S. 1987. 5,6-dichloroindole-3-acetic acid as a potent auxin: its synthesis and biological activity. Experientia 43, 1237–1239.
Hedrich R, Bregante M, Dreyer I, Gambale F. 1995. The voltage-dependent potassium-uptake channel of corn coleoptiles has permeation properties different from other K+ channels. Planta 197, 193–199.
Hertel R. 1994. A critical review on proposed hormone action: the example of auxin. In: Smith CJ et al., eds. Biochemical mechanisms involved in plant growth regulation. Oxford: Clarendon Press, 1–15.
Hertel R. 1995. Auxin binding protein 1 is a red herring. Journal of Experymental Botany 46, 461–462.
Hofinger M, Böttger M. 1979. Identification by GC-MS of 4-chloroindolylacetic acid and its methyl ester in immature Vicia faba seeds. Phytochemistry 18, 653–654.
Huizen R, Ozga JA, Reinecke DM, Twitchin B, Mander LN. 1995. Seed and 4-chloroindole-3-acetic acid regulation of gibberellin metabolism in pea pericarp. Plant Physiology 109, 1213–1217.[Abstract]
Jacobs M, Lomax T, Hertel R. 1984. A comparison of the auxin specificity of medium acidification and elongation in maize coleoptiles. Plant Science Letters 34, 35–41.
Karcz W, Burdach Z. 1995. Effect of temperature on the IAA, 4-Cl-IAA and FC-induced growth and H+-extrusion in Zea mays L. coleoptile segments. In: 10th International Workshop on Plant Membrane Biology. Regensburg, August 6–11, Abstract S 16.
Karcz W, Lüthen H, Böttger M. 1996. Comparative investigation of IAA and 4-Cl-IAA-induced growth and proton secretion in maize coleoptile segments. Plant Physiology and Biochemistry, Special Issue, Abstract S01-14, page 7.
Karcz W, Lüthen H, Böttger M. 1999. Effect of IAA and 4-Cl-IAA on growth rate in maize coleoptile segments. Acta Physiologiae Plantarum 21, 133–139.
Karcz W, Stolarek J. 1988. Effect of UV-C radiation on extension growth, H+-extrusion and transmembrane electric potential in maize coleoptile segments. Physiologia Plantarum 74, 770–774.
Karcz W, Stolarek J, Lekacz H, Kurtyka R, Burdach Z. 1995. Comparative investigation of auxin and fusicoccin-induced growth and H+-extrusion in coleoptile of Zea mays L. Acta Physiologiae Plantarum 17, 3–8.
Karcz W, Stolarek J, Pietruszka M, Malkowski E. 1990. The dose–response curves for IAA-induced elongation growth and acidification of the incubation medium of Zea mays L. coleoptile segments. Physiologia Plantarum 80, 257–261.
Katayama M, Thiruvikraman SV, Marumo S. 1987. Identification of 4-chloroindole-3-acetic acid and its methyl ester in immature seeds of Vicia amurensis (the tribe Vicieae) and their absence from three species of Phaseoleae. Plant Cell Physiology 28, 383–386.
Keller CP, Van Volkenburgh E. 1996. The electrical response of Avena coleoptile cortex to auxins: evidence in vivo for activation of a Cl- conductance. Planta 198, 404–412.
Kutschera U. 1994. The current status of the acid-growth hypothesis. New Phytologist 126, 549–569.
Kutschera U, Schopfer P. 1985a. Evidence against the acid-growth theory of auxin action. Planta 163, 483–493.
Kutschera U, Schopfer P. 1985b. Evidence for the acid-growth theory of fusiccocin action. Planta 163, 494–499.
Lohse G, Hedrich R. 1992. Characterization of the plasma-membrane H+-ATPase from Vicia faba guard cells. Modulation by extracellular factors and seasonal changes. Planta 188, 206–214.
Lüthen H, Bigdon M, Böttger M. 1990. Re-examination of the acid-growth theory of auxin action. Plant Physiology 93, 931–939.
Lüthen H, Böttger M. 1988. Kinetics of proton secretion and growth in maize roots: action of various plant growth effectors. Plant Science 54, 37–43.
Lüthen H, Böttger M. 1992. A high tech low cost auxanometer for high resolution determination of elongation rates in six simultaneous experimental set-ups. Mittelung Institut Allgemeine Botanik Hamburg 24, 13–22.
Lüthen H, Böttger M. 1993. Induction of elongation in maize coleoptiles by hexachloroiridate and its interrelation with auxin and fusicoccin action. Physiologia Plantarum 89, 77–86.
Lüthen H, Claussen M, Böttger M. 1999. Growth: progress in auxin research. Cell Biology and Physiology, Progress in Botany 60, 315–340.
Macdonald H. 1997. Auxin perception and signal transduction. Physiologia Plantarum 100, 423–430.
Marrè E. 1979. Fusicoccin: a tool in plant physiology. Annual Review of Plant Physiology 30, 273–288.[Web of Science]
Marten I, Lohse G, Hedrich R. 1991. Plant growth hormones control voltage-dependent activity of anion channels in the plasma membrane of guard cells. Planta 353, 1–4.
Marumo S, Hattori H, Abe H, Munakata K. 1968. Isolation of 4-chloroindolyl-3-acetic acid from immature seeds of Pisum sativum. Nature 219, 959–960.[Medline]
Moore TS. 1989. Biochemistry and physiology of plant hormones, 2nd edn. New York: Springer-Verlag Inc., 28–85.
Napier RM, Venis MA. 1995. Auxin action and auxin-binding proteins. New Phytologist 129, 167–201.
Normanly J. 1997. Auxin metabolism. Physiologia Plantarum 100, 431–442.
Normanly J, Slovin JP, Cohen JD. 1995. Rethinking auxin biosynthesis and metabolism. Physiologia Plantarum 107, 323–329.
Ozga JA, Brenner ML. 1992. The effect of 4-Cl-IAA on growth and GA metabolism in deseeded pea pericarp (abstract No. 12). Plant Physiology 99, S-2.
Ozga JA, Reinecke DM, Brenner ML. 1993. Quantitation of 4-Cl-IAA and IAA in 6 DAA pea seeds and pericarp (abstract No. 28). Plant Physiology 102, S-7.
Peters WS, Felle H. 1991a. Control of apoplast pH in corn coleoptile segments. I. The endogenous regulation of cell wall pH. Journal of Plant Physiology 137, 655–661.
Peters WS, Felle H. 1991b. Control of apoplast pH in corn coleoptile segments. II. The effect of various auxins and auxin analogues. Journal of Plant Physiology 137, 691–696.
Peters WS, Lommel C, Felle H. 1997. IAA breakdown and its effect on auxin-induced cell wall acidification in maize coleoptile segments. Physiologia Plantarum 100, 415–422.
Peters WS, Lüthen H, Böttger M, Felle H. 1998. The temporal correlation of changes in apoplast pH and growth rate in maize coleoptile segments. Australian Journal of Plant Physiology 25, 31–35.
Peters WS, Richter U, Felle HH. 1992. Auxin-induced H+–pump stimulation does not depend on the presence of epidermal cells in corn coleoptiles. Planta 186, 313–316.
Pless T, Böttger M, Hedden P, Grabe J. 1984. Occurrence of 4-Cl-indoleacetic acid in broad beans and correlation of its levels with seed development. Plant Physiology 74, 320–323.
Rayle DL, Cleland RE. 1970. Enhancement of wall loosening and elongation by acid solutions. Plant Physiology 46, 250–253.
Rayle DL, Cleland RE. 1992. The acid-growth theory of auxin induced cell elongation is alive and well. Plant Physiology 99, 1271–1274.
Reinecke DM. 1999. 4-Chloroindole-3-acetic acid and plant growth. Plant Growth Regulation 27, 3–13.
Reinecke DM, Ozga JA, Ili
N, Magnus V, Koji-Prodi B. 1999. Molecular properties of 4-substituted indole-3-acetic acids affecting pea pericarp elongation. Plant Growth Regulation 27, 39–48.
Reinecke DM, Ozga JA, Magnus V. 1995. Effect of halogen substitution of indole-3-acetic acid on biological activity in pea fruit. Phytochemistry 40, 1361–1366.
Rescher U, Walther A, Schiebl C, Klämbt D. 1996. In vitro binding affinities of 4-chloro-, 2-methyl-, 4-methyl-, and 4-ethyl-indoleacetic acid to auxin-binding protein 1 (ABP1) correlate with their growth-stimulating activities. Journal Plant Growth Regulation 15, 1–3.
Rücke A, Palme K, Venis MA, Napier RM, Felle HH. 1993. Patch-clamp analysis establishes a role for an auxin binding protein in the auxin stimulation of plasma membrane current in Zea mays protoplasts. The Plant Journal 4, 41–46.[Web of Science]
Schopfer P. 1993. Determination of auxin-dependent pH changes in coleoptile cell walls by a null-point method. Plant Physiology 103, 351–357.[Abstract]
Senn AP, Goldsmith MHM. 1988. Regulation of electrogenic proton pumping by auxin and fusicoccin as related to the growth of Avena coleoptiles. Plant Physiology 88, 131–138.
Stolarek J, Karcz W. 1987. Effects of UV-C radiation on membrane potential and electric conductance in internodal cells of Nitellopsis obtusa. Physiologia Plantarum 70, 473–478.
Stotz HU, Hertel R. 1994. Re-evaluation of the role of auxin binding site II. Journal of Plant Growth Regulation 13, 79–85.
Venis MJ. 1995. Auxin binding protein 1 is a red herring? Oh no it isn't! Journal of Experimental Botany 46, 463–465.
Venis MA, Napier RM. 1991. Auxin receptors: recent developments. Plant Growth Regulation 10, 329–340.
Venis MA, Napier RM, Oliver S. 1996. Molecular analysis of auxin-specific signal transduction. Plant Growth Regulation 18, 1–6.
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