Osmoregulation in Rice Coleoptile Elongation as Promoted by Cooperation between IAA and Ethylene

IAA-induced elongation of rice (Oryza sativa L. cv. Sasanishiki)coleoptiles is regulated by cooperation between IAA and ethyleneproduced in response to IAA. However, the presence of some solutes,such as K^$, Na^$, Rb^$, glucose and sucrose, in the incubationmedia was found to be indispensable for this cooperation. Withoutthose solutes, the IAA-induced elongation was not sustainedover a long time period. IAA caused increases in both the osmoticpotentials of the coleoptile cells and the extensibility oftheir cell wall. In epidermal cells of IAA-treated coleoptiles,the osmotic potential increased from –0.87 to –0.62MPa during a 4-h incubation with 1 mM KCl. Moreover, IAA promotedthe uptake of K^$ or Na^$ from the media into the coleoptiles.However, these effects of IAA were partially prevented by aminoethoxyvinylglycine(AVG), and all the AVG effects were completely nullified byethylene applied simultaneously and exogenously. Both IAA andethylene did not affect the wall yield stress. These resultssuggested that the long-term elongation induced by IAA in ricecoleoptile segments results from inhibiting increases in osmoticpotentials of their cells. The maintenance by IAA of low osmoticpotentials may be partly due to the promotive action of ethyleneproduced in response to IAA on the solute uptake from the media. (Received July 6, 1983; Accepted February 15, 1984)     

Overexpression of OsJAC1, a Lectin Gene, Suppresses the Coleoptile and Stem Elongation in Rice

Lectin plays an Important role In defense signaling In plants, but its function In plant growth and development is not well known. Previously, we cloneds rice （Oryza sativa L.） gene OsJAC1 encoding s msnnose-blndlng Jscslln-relsted lectln, and found that OsJAC1 was Jssmonlc acid （JA） Inducible. Here we cloned the promoter of OsJAC1, and GUS activity was detected In young roots, coleoptlles, sheaths, leaves, nodes of stems, stems, rschlses, pistils, stsmens and lemmss of OsJAC1：：GUS trsnsgenlc rice, suggesting that OsJAC1 Is s constitutive expression gene In rice. Moreover, OsJAC1-overexpressed （Ubi：：OsJAC1） rice showed dwarfism with shorter coleptlles resulting from the failure of cell elongation of coleoptlles. In addition, compared with coleoptlles of wild-type plants, those of OsJAC1 overexpresslon rice were more sensitive to JA treatment. These data revealed that, besides Its roles in defense response, lectin plays an Important role in rice growth and development.     

Mining Favorable Alleles for Rice Coleoptile Elongation Length Sensitivity to Exogenous Gibberellin Under Submergence Condition

Journal of Plant Growth Regulation - High sensitivity of rice coleoptile elongation length to exogenous gibberellin is a beneficial trait to utilize superior rice cultivars that could not be used...     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. II. Cultivar Differences

The relationship between coleoptile elongation and survivalvs. alcoholic fermentation of rice under anoxia is examinedusing eight cultivars differing in submergence tolerance. Anoxiawas imposed on either 1 or 4 d aerated seeds either by N₂ flushingsubmerged tissues or by incubating tissues in stagnant deoxygenatedagar at 0·1% w/v; the latter simulated the stagnant conditionsof waterlogged soil. Two cultivars that were most tolerant tosubmergence also had the greatest tolerance to anoxia, whilea submergence intolerant cultivar was also intolerant to anoxia. Coleoptile growth under anoxia was related to rates of ethanolsynthesis (R_E), however differences between growth during anoxiaand survival after anoxia indicated that post-anoxic injurymay also be important in rice seeds exposed to anoxia. The correlationbetween coleoptile growth and R_E measured on a tissue basisusing intact seeds was r² = 0·67 among six varietiesover 0-3 d anoxia. This correlation improved to about r² = 0·85using R_E of (embryos plus coleoptiles) over 0-3 d, or coleoptilesat 3 d after anoxia. Coleoptile growth of individual seeds wasusually poorly correlated to R_E in these cultivars at 2-3 dafter anoxia. When coleoptiles of similar lengths were obtainedfrom different cultivars using 4 d aerated seeds, there weredifferences in R_E and coleoptile growth which were related tocoleoptile growth during 3 or 5 d anoxia, either on a tissue(r² = 0·85) or a fresh weight basis (r² = 0·70-0·97respectively). Results are discussed in relation to factorswhich may limit ethanol synthesis in rice exposed to anoxiaand the importance of growth to the survival of seeds and matureplants during submergence in the natural environment.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Inhibition of Cell Elongation in Avena Coleoptile by Hydroxyproline

A study has been made of the hydroxyproline-induced inhibition of elongation of Avena coleoptile tissues. The isomers of 4-hydroxyproline differ in their effectiveness; only the L isomers are growth inhibitors with the cis form (allohydroxyproline) being more effective than the trans form (hydroxyproline).Hydroxyproline differs from other amino acid antagonists and protein synthesis inhibitors in respect to 2 characteristics of the growth inhibition. First, a certain increment of auxin-induced elongation must take place following addition of hydroxyproline before the growth is inhibited. In contrast, pretreatment with other amino acid antagonists or protein synthesis inhibitors completely eliminates the ability of Avena coleoptile sections to respond to auxin. Secondly, sucrose markedly increases the magnitude of the hydroxyproline inhibition; i.e., sucrose acts to inhibit rather than promote growth when in the presence of hydroxyproline.It appears that hydroxyproline is a specific inhibitor for the synthesis of some factor which is utilized in elongation. Following addition of hydroxyproline, auxin-induced elongation continues until the pool of this factor is exhausted; then elongation is inhibited.     

Direct and Synergistic Influence of Tweens on Avena Coleoptile Section Elongation

The Avena cylinder test was used with Tweens at 3 different concentrations with and without the addition of varying concentrations of IAA. Tween 20 was a toxic substance for oat coleoptile sections at such concentration as 0.1 %. Tween 40 gave erratic results and Tween 80 has practically no direct effect on cell elongation. An inhibitory effect continues to increase with increasing HLB values. The second object of this experiment was to ascertain whether cell elongation promoted by IAA would be enhanced by osmotic substances such as Tweens, as consequence of a specific modification in the permeability when the membranes are lipid in nature. The hypothesis was supported by the experimental work when 0.05 % Tweens were assayed although the inverse was also true, with concentrations of Tweens as low as 0.01 %. Accordingly, evidence must be verified by further investigation.     

玉米胚芽鞘细胞伸长生长与富含羟脯氨酸蛋白质的关系

玉米胚芽鞘细胞伸长生长进程中,富含羟脯氨酸蛋白质的合成速率同细胞的伸长生长呈负相关,迅速伸长期较低,而伸长近终止阶段出现活性高峰。生长素促进的伸长生长与富含羟脯氨酸蛋白质的合成、累积相关。IAA使胚芽鞘高体切段细胞的伸长生长增加4倍多,细胞中较低的羟脯氨酸蛋白质的合成速率似有利于生长素的促进效应。生长素对伸长细胞中羟脯氨酸蛋白质的转运和在壁中累积有抑制作用。     

Requirement of RNA for the Auxin-induced Elongation of Oat Coleoptile

Using etiolated oat coleoptile segments the following results were obtained. Actinomycin D pretreatment for one hour produced about 50 per cent inhibition of RNA synthesis (labeled uracil incorporation), but the elongation caused by IAA was not inhibited in the following 5 hours at least. Actinomycin D pretreatment for three hours produced about 75 per cent inhibition of RNA synthesis and almost complete inhibition of subsequent IAA-induced elongation, which is accompanied by the inhibition of IAA-induced increase in cell wall extensibility. The inhibiting effect of actinomycin D seemed to be reduced when IAA was given within a certain period.     

Rapid Inhibition of Auxin-induced Elongation of Avena Coleoptile Segments by Cordycepin

The effects of cordycepin (3'-deoxyadenosine), an RNA synthesis inhibitor, on auxin-induced elongation in Avena coleoptile segments were studied with a position-sensing transducer. Cordycepin rapidly inhibited auxin-stimulated growth in the coleoptile segments whether added before, at the same time as, or after, the 2 mum auxin treatment. Midcourse additions of 100, 50, and 25 mug/ml cordycepin inhibited auxin-promoted elongation in an average of 18, 22, and 35 minutes, respectively. Additions of cordycepin before or at the same time as the auxin treatment partially inhibited the magnitude of the subsequent auxin-promoted growth but did not appreciably alter the latent period of the auxin response. It was concluded that if cordycepin is inhibiting the synthesis of RNA required for growth, the decay time for this RNA may be considerably shorter than that suggested in the literature from actinomycin D experiments. Preliminary kinetic evidence indicated that cordycepin does not inhibit auxin-induced elongation by acting as a respiratory inhibitor. Studies in mung bean shoot mitochondria demonstrated that cordycepin has no effect on respiration, respiratory control, or ADP/oxygen ratios.     

Antagonism Between Malate and Ethylene in the Regulation of Avena sativa Coleoptile Elongation

Etiolated Avena sativa L. coleoptile sections were used to determinethe influence of C₂H₄ on in vivo and in vitro rates of CO₂ fixation,and to measure the influence of various permutations of C₂H₄,CO₂, and malate on growth. Whereas 1 mM malate or 320 µI^-1 CO₂ stimulated growth by approximately 100 per cent, inhibitionof growth by 10-8 µ I_-1 C₂H₄ was substantial only in thepresence of malate or CO₂ The increase in growth rate in responseto these two agents was eliminated by the simultaneous applicationof C₂H₄. The in vivo rate of dark [¹⁴C]bicarbonate fixationand in vitro enzymic assays of fixation were not measurablyinhibited by C₂H₄. These results are discussed in the lightof evidence which indicates that CO₂-stimulated growth is mediatedby dark fixation. The data do not support the view that C₂H₄inhibition of growth results from an inhibition of fixation,but suggests that C₂H₄ may inhibit some step in the processby which malate stimulates growth.     

The Effect of Gibberellin on Tryptophan Conversion and Elongation of the Avena Coleoptile

Gibberellic acid (GA₃) enhanced directly the release of ¹⁴CO₂ from tryptophan-1-^l4C by cell free preparations of Avena coleoptile tips. The rate of tryptophan metabolism in the presence of GA₃ was increased by approximately 100 per cent. The addition of auxin synthesis inhibitors to incubation flasks nullified the enhancement effect of GA₃ on elongation of the coleoptile tips. These studies implicate tryptamine as an intermediate in the formation of auxin from tryptophan. The possibility of GA₃-IAA interaction in the elongation processes was also investigated. Combination treatments of these growth-promoting substances did not induce a synergistic growth response by the coleoptile tissue.     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. I. Importance of Treatment Conditions and Different Tissues

The relationship between coleoptile elongation and alcoholicfermentation of rice under anoxia is examined using seeds either:(a) N₂ flushed during submergence, (b) incubated in stagnantdeoxygenated agar at 0·1% w/v to simulate the stagnantconditions of waterlogged soil, or (c) incubated in waterloggedsoil. Coleoptile elongation growth was greater for N₂ flushing> stagnant agar > soil; seed survival was also greatestin this order over 1-5 d. Ethanol concentrations in coleoptiles and intact seeds (cv.IR42) were approximately 300 and 100 mol m^-3 respectively whenseeds were grown 3 d in stagnant agar, however 92% of the ethanolin seeds diffused into the external medium when solutions weremixed for 5-10 s. Coleoptile growth under anoxia was relatedto rates of ethanol synthesis (R_E) in different treatments;there was greater coleoptile growth and R_E for seeds in N₂ flushedsolutions than in stagnant deoxygenated agar. Coleoptile growthof individual seeds was also related to the R_E of each seedat 2-3 d after anoxia (r² = 0·46). Analysis of different tissues was important in evaluating growthand metabolism of coleoptiles. Although the coleoptile onlyaccounted for 0·7% of seed dry weight at 3 d after anoxia,it contained 21% of the ethanol produced by rice seeds. Therewere also three-fold higher rates of R_E on a fresh weight basisin expanding tissues in the base of the coleoptile relativeto the elongated tissues at the apex. Results are discussedin terms of the importance of environmental conditions usedto impose anoxia, quantification of R_E in specific tissues andthe possibility that under stagnant conditions high ethanolconcentrations in tissues may limit R_E and coleoptile growth.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Hydroxyproline Formation and Its Relation to Auxin-induced Cell Elongation in the Avena Coleoptile

A study has been made of the effects on hydroxyproline formation of 4 factors that influence the rate of cell elongation in the Avena coleoptile; auxin, sugars, an external osmoticum, and actinomycin D. Hydroxyproline formation is increased by a combination of auxin and sucrose, but is affected to a much lesser extent by either factor alone. Its formation is inhibited by an external osmoticum but is scarcely affected by actinomycin D. The lack of correlation between the amount of hydroxyproline synthesis and the growth rate suggests that hydroxyproline formation is not involved in the actual process of wall loosening. It is suggested, instead, that if the wall is to retain its capacity for rapid extension, those hemicelluloses which are incorporated into it by intussusception rather than by apposition must be attached to a hydroxyproline-protein.     

A Synergistic Stimulation of Avena sativa Coleoptile Elongation by Indoleacetic Acid and Carbon Dioxide

The ability of 0.03% CO₂ to stimulate growth has been investigated using etiolated Avena coleoptile sections maintained in buffered solution. This concentration of CO₂-stimulated growth after a lag period of 12 to 15 minutes, and a synergistic relationship between indoleacetic acid and CO₂ in stimulating growth has been demonstrated. The response to CO₂ is inhibited by cycloheximide and is lost approximately 10 minutes after exposure to CO₂-free air. Malate can replace CO₂ in stimulating growth. In the light of these data and recent literature on a growth response of coleoptile sections to CO₂-saturated solutions, the existence of two mechanisms of CO₂-simulated growth is proposed. In addition, it is suggested that growth promotion by 0.03% CO₂ is mediated by a process involving dark CO₂ fixation.     

水稻茎伸长生长与植物激素

赤霉素（GA）,生长素（IAA）,脱落酸（ABA）和乙烯影响水稻茎（或节间）的伸长,其中赤霉素与水稻茎伸长生长的关系最密切。GA1是植物体内刺激茎伸长的至关重要的赤霉素,GA3已作为最常用的外源激素诱导水稻的节间伸长。水稻茎秆的伸受激素浓度和敏感性的双重控制,激素浓度或敏感性任一方的改变都有可能导致株高的变异。赤霉素如此显著地促进茎的伸长可能与增加细胞分裂和促使细胞壁松弛有关。而生长素主要促进细胞伸长。植物激素促进水稻茎长的分子机理的研究已有较大的进展,预期这方面的研究和应用在未来几年内将有新的突破。