生长调节剂调控龙眼冲梢的研究

为高效、安全地调控龙眼冲梢,在龙眼花芽形态分化开始期(露红点期)和花穗主轴长6～9 cm的花穗展叶期,施用生长调节剂,比较了不同方法调控龙眼冲梢的效果。结果发现龙眼花芽形态分化开始期树冠喷施200 mg/kg乙烯利+150 mg/kg多效唑混合液和土施多效唑每株4 g处理控冲梢效果都显著高于对照,冲梢率分别是10.5%和7.6%,在花穗小叶处于展叶期虹吸输300 mg/kg乙烯利防控龙眼冲梢有效且安全。     

Effect of applied and endogenous indol-3-yl-acetic acid on maize root growth

The level of endogenous Indol-3-yl-acetic acid (IAA) measured by gas chromatography-mass spectrometry in the elongating zone of intact primary roots of Zea mays showed a good linear correlation with the growth rate of these roots. When they were treated with IAA, their relative elongation decreased; this indicates a supraoptimal content of endogenous IAA. However, the growth of some of the relatively rapidly extending roots was enhanced by such treatment. Interactions between endogenous and applied IAA in the control of root growth are discussed.Abbreviations GC-MS gas chromatography-mass spectrometry - IAA Indol-3-yl-acetic acid     

Synergistic interaction of gibberellic acid and triazinone derivatives in the promotion of rice shoot growth

Forty-five 1,3,5-triazine-2,6-dione derivatives were synthesized and their plant growth-promoting activities examined by the rice (Oryza sativa) seedling test in the presence or absence of gibberellic acid (GA). For high activity in promoting the growth of rice seedlings and acting as active GA-synergists, a para-substituted or a 2,4-disubstituted phenyl group, a hydrogen atom and an alkoxy group were required in the 1-, 3- and 4-positions of the 1,3,5-triazine-2,6-dione molecule. 4-Ethoxy-1-(p-tolyl)-s-triazine-2,6(1H, 3H)-dione [TA], one of the most potent triazinones, synergized the effect of GA on the shoot elongation of different varieties of rice including normal type, dwarf mutants and chlorophyll-mutants. TA synergistically increased the growth-promoting activity of GA by both a simultaneous treatment at the same sites and separate treatments at separate sites of rice seedlings.     

Factors increasing ethylene production enhance the sensitivity of root growth to auxins

Light inhibits root elongation, increases ethylene production and enhances the inhibitory action of auxins on root elongation of pea ( Pisum sativum L. cv. Weibulls Marma) seedlings. To investigate the role of ethylene in the interaction between light and auxin, the level of ethylene production in darkness was increased to the level produced in light by supplying 1-aminocyclopropane-1-carboxylic acid (ACC) or benzylaminopurine (BAP). Ethylene production was measured in excised root tips after treatment of intact seedlings for 24 h, while root growth was measured after 48 h. Auxin, at a concentration causing a partial inhibition of root elongation, did not increase ethylene production significantly. A 4-fold increase in ethylene production, caused either by light, 0.1 μ M ACC or 0.1 μ M BAP, inhibited root elongation by 40–50%. The auxins 2,4-dichlorophenoxyacetic acid and indolebutyric acid applied at 0.1 μ M inhibited root elongation by 15–25% in darkness but by 50–60% in light. Supply of ACC or BAP in darkness enhanced the inhibitory effects of auxins to about the same extent as in light. The inhibition caused by the auxins as well as by the BAP was associated with swelling of the root tips. ACC and BAP treatment synergistically increased the swelling caused by auxins. We conclude that auxin and ethylene, when applied or produced in partially inhibitory concentrations, act synergistically to inhibit root elongation and increase root diameter. The effect of light on the response of the roots to auxins is mediated by a light-induced increase in ethylene production.     

Synergistic action of auxin and cytokinin mediates aluminum‐induced root growth inhibition in Arabidopsis

Auxin acts synergistically with cytokinin to control the shoot stem‐cell niche, while both hormones act antagonistically to maintain the root meristem. In aluminum (Al) stress‐induced root growth inhibition, auxin plays an important role. However, the role of cytokinin in this process is not well understood. In this study, we show that cytokinin enhances root growth inhibition under stress by mediating Al‐induced auxin signaling. Al stress triggers a local cytokinin response in the root‐apex transition zone (TZ) that depends on IPTs, which encode adenosine phosphate isopentenyltransferases and regulate cytokinin biosynthesis. IPTs are up‐regulated specifically in the root‐apex TZ in response to Al stress and promote local cytokinin biosynthesis and inhibition of root growth. The process of root growth inhibition is also controlled by ethylene signaling which acts upstream of auxin. In summary, different from the situation in the root meristem, auxin acts with cytokinin in a synergistic way to mediate aluminum‐induced root growth inhibition in Arabidopsis.     

Changes in root-shoot ratio and ion uptake of maize (Zea mays L.) from soil as influenced by a plant growth regulator

A pot experiment with maize cv. Limac was conducted to investigate the influence of BAS 110.. W, a plant growth regulator (PGR), on root and shoot development and nutrient uptake. The PGR was applied via the soil with 0, 5, 10, 20, and 40 mg a.i. per pot. Shoot dry matter production was reduced to a higher degree than root length, resulting in a higher root-shoot ratio (RSR) of the treated plants. Shoots of treated plants contained higher concentrations of N, P, Ca, Mg, and unchanged K concentrations. The alterations in concentration could be explained by the changes in RSR induced by the plant growth retardant. The effect was strongest with P (+40%) which was limited by soil supply. N, Ca, and Mgconcentrations were positively influenced (+20%), there was no increase for Kvs RSR.     

独脚金内酯调控植物侧枝发育的分子机制及其与生长素交互作用的研究进展

对独脚金内酯（strigolactones,SLs）调控植物侧枝发育的分子机制及其与生长素相互作用的相关研究结果进行了总结和归纳,在此基础上提出今后的重点研究方向。相关的研究结果显示：在拟南芥[Arabidops~thaliana（Linn．）Heynh．]、豌豆（Pisum sativum Linn．）和水稻（Oryza sativa Linn．）等植物多枝突变体中SLs作为可转导信号参与侧枝发育的分子调控,从这些植物中已克隆获得参与SLs生物合成及信号应答途径的一些基因。作为一种植物激素,SLs在侧枝发育调控网络中与生长素相互作用;腋芽发育与其中生长素的输出密切相关,SLs通过调控芽中生长素的输出间接抑制腋芽发育和侧枝生长,而生长素则在SLs生物合成中起调节作用。     

Developmental changes in the gibberellin-induced growth response in stem segments of light-grown pea genotypes

The effects of GA on stem elongation were studied using segments from one tall and three dwarf light-grown pea genotypes varying in endogenous hormone content. Stem segments were cut at two distinct ages: when the fourth internode was at about 6–13% of full expansion (early-expansion) or at 18–25% of full expansion (mid-expansion). Light microscopy and flow cytometry were used to demonstrate that GA does not induce cell division in excised pea stem segments. The growth studied here was strictly elongation. Measurement of final segment length after 48 hours and high resolution measurement of growth kinetics over 20 hours using an angular position transducer were done on segments treated with hormone solutions. Our data indicate that the action of GA on stem elongation can be classified into two distinct modes. The first, apparent in early-expansion stem segments, shows distinct growth kinetics and is independent of the endogenous IAA concentration of the segments. Quantitation of IAA by GC/MS in early-expansion segments of wild type pea incubated with gibberellin shows that an increase in IAA concentration is part of the GA response in such segments. The second mode of GA action is evinced in mid-expansion segments. Whereas there is no short term (<20 h) response to GA alone (as determined by growth kinetics), there is a long term (48 h) response whose magnitude decreases across the genotypes with decreasing endogenous hormone content. Growth responses indicate that in mid-expansion segments exogenous GA acts by enhancing IAA action but appears to be unable to augment endogenous IAA content. Contradictory reports of the response of excised stem segments to GA can be reconciled when tissue genotype and developmental stage are considered.     

植物生长调节物质IP－1号对木薯产量及其生物性状的影响

１９９０和１９９１年在木薯（ＭａｎｉｈｏｔｅｓｃｕｌｅｎｔａＣｒａｎｔｚ）生长期以植物生长调节物质ＩＰ－１号０,２０,３０和４０ｐｐｍ进行叶面喷洒,结果表明：３０ｐｐｍ处理可使木薯块根产量平均增加５４．４４％,块根淀粉含量平均提高２０．８１％。单株最大薯重提高３１．５５％,块根数增加２１．１７％,块根长度增长１７．６２％,地上部鲜重增加３４．３６％,植株高度增加４．３６％,植株收获期保留青叶数增加１９．４２％,主茎直径增加６．２６％,块根直径增加２．５８％,叶片的叶绿素和蛋白质含量分别提高５．５７％和２５．９６％,叶片光合作用强度提高１５．８６％,而对主茎高度、主茎节数没有明显影响。     

Comparison of the effects of nitrate and ammonium forms of nitrogen on auxin content in roots and the growth of plants under different temperature conditions

Average root length, root/shoot ratio and auxin content in roots were higher in plants supplied with nitrate rather than ammonium and grown at 18, 21, 24°C. The effects on root length were most pronounced at the highest temperatures (21 and 24°C); and the warmer the temperature, the earlier appearance of the differences in growth rate between NO₃- and NH₄-fed plants. A sharp acceleration of root growth was characteristic of NO₃-fed plants grown at 21 and 24°C and was associated with a temporary increase in auxin concentration measured by immunoassay.     

No effect of the plant growth regulator, chlormequat, on boar fertility

Chlormequat is a commonly used plant growth regulator in agriculture. Defined levels of chlormequat residue are allowed in food and an acceptable daily intake is defined for humans. However, there are results in the literature suggesting that a daily intake below the acceptable level for human is detrimental for mammalian reproduction. In the present experiment we investigated the effect of chlormequat at levels up to that acceptable for humans on reproduction in male pigs. Chlormequat (also known as chlorocholine chloride (CCC)) was mixed into the diet and given to the experimental animals at three levels (three treatment groups), i.e. 0 mg CCC/kg BW per day (Control), 0.025 mg CCC/kg BW per day and 0.05 mg CCC/kg BW per day. Eight mother sows per treatment group were used in the experiment. From the day of insemination, the mother sows received the experimental diets. The piglets were weaned at 4 weeks of age and two boar littermates continued on the same treatment as the dam until maturity and delivery of semen for in vitro fertilization (IVF) and in vivo fertilization. Semen volume, sperm concentration and fraction of live sperms were not (P 0.46) detrimentally affected by chlormequat intake. The fraction of oocytes developing to more than the one-cell stage at day 5 after IVF was not (P = 0.88) detrimentally affected by chlormequat intake. Chlormequat intake did not detrimentally affect the fraction of gilts being pregnant after one insemination (P = 0.65) or the number of embryos in the pregnant gilts (P = 0.36). Serum chlormequat concentration was 0.9 μg/kg in the 0.025 mg CCC/kg BW per day group and 1.8 μg/kg in the 0.05 mg CCC/kg BW per day group, but was below the detection limit in control animals. In conclusion, the plant growth regulator chlormequat could not be proven to be detrimental to the selected reproduction traits in male pigs. This is in contrast to existing results from the male mouse.     

Relationship between root elongation rate and diameter and duration of growth of lateral roots of maize

The objective of this work was to describe the relationship between elongation rate and diameter of maize roots and to estimate the length and growth duration of lateral roots of maize. Diameters and elongation rates of roots were measuredin situ on plants grown 5 weeks in small rhizotrons under greenhouse conditions. At the end of the experimental period the roots were harvested and diameters of axile and lateral roots were measured. The frequency distribution of diameters of harvested roots was bimodal with a minimum at 0.6 mm; 97% of axile roots were larger than this value and 98% of the lateral roots were smaller. Root elongation per day increased as diameter increased but the slope of the relationship with lateral roots was about 2.5 times that with axile roots when separate linear regressions were fitted to the two populations. The length of lateral roots found on axillary roots between the base and about 30 cm from the apex was approximately 2.2 cm. All of the data was consistent with the hypothesis that the lateral roots grew for about 2.5 days and then ceased growing. The axillary roots continued to grow throughout the experimental period at a rate of about 3 cm day⁻¹. Contribution from the Department of Agronomy, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853. Agronomy paper No. 1661. This research is part of the program of the Center for Root-Soil Research.     

Rooting, growth and ethylene evolution of pea cuttings in response to chloroindole auxins

In pea cuttings ( Pisum sativum L. cv. Alaska) we measured shoot and root growth and ethylene production in response to 4-chloroindole-3-acetic acid (4-CI-IAA) or 4,6-dichloroindole-3-acetic acid (4,6-Cl₂-IAA). Leafy cuttings treated basally with either of the chlorinated auxins in high concentrations showed permanent epinasty, loss of apical growth and dominance resulting in the outgrowth of laterals from the lower-most axillary bud. The naturally occurring 4-CI-IAA was a better root promoter than the synthetic 4,6-Cl₂-IAA which inhibited rooting. Both chloroindole auxins induced very high ethylene evolution, which lasted much longer than the ethylene evolution after IAA treatment.     

Effect of sub-optimal root zone temperatures at varied nutrient supply and shoot meristem temperature on growth and nutrient concentrations in maize seedlings (Zea mays L.)

Maize seedlings were grown for 10 to 20 days in either nutrient solution or in soils with or without fertilizer supply. Air temperature was kept uniform for all treatments, while root zone temperature (RZT) was varied between 12 and 24°C. In some treatments the basal part of the shoot (with apical shoot meristem and zone of leaf elongation) was lifted up to separate the indirect effects of root zone temperature on shoot growth from the direct effects of temperature on the shoot meristem.Shoot and root growth were decreased by low RZT to a similar extent irrespective of the growth medium (i.e. nutrient solution, fertilized or unfertilized soil). In all culture media Ca concentration was similar or even higher in plants grown at 12 as compared to 24°. At lower RZT concentrations of N, P and K in the shoot dry matter decreased in unfertilized soil, whereas in nutrient solution and fertilized soil only the K concentration decreased.When direct temperature effects on the shoot meristem were reduced by lifting the basal part of the shoot above the temperature-controlled root zone, shoot growth at low RZT was significantly increased in nutrient solution and fertilized soil, but not in unfertilized soil. In fertilized soil and nutrient solution at low RZT the uptake of K increased to a similar extent as plant growth, and thus shoot K concentration was not reduced by increasing shoot growth rates. In contrast, uptake of N and P was not increased, resulting in significantly decreased shoot concentrations.It is concluded that shoot growth at suboptimal RZT was limited both by a direct temperature effect on shoot activity and by a reduced nutrient supply through the roots. Nutrient concentrations in the shoot tissue at low RZT were not only influenced by availability in the substrate and dilution by growth, but also by the internal demand for growth.     

Plant-derived smoke solutions stimulate the growth of Lycopersicon esculentum roots in vitro

Aqueous extracts of smoke, derived from Themeda triandra, a fire-climax grass, and Passerina vulgaris, a fynbos plant, stimulated the growth of primary root sections of tomato roots in suspension culture. The optimal dilution for both extracts was 1:2000. Several of the fractions obtained from TLC separation of the Themeda and the Passerina extracts significantly promoted primary root growth. The auxins naphthaleneacetic acid (NAA), indolebutyric acid (IBA) and indoleacetic acid (IAA) were found to stimulate the growth of the primary root axis, with IAA and NAA significantly promoting lateral root number. Similarly, the naturally occurring cytokinins, zeatin and its derivatives (zeatin-O-glucoside; dihydrozeatin and zeatin riboside) stimulated primary root length. Zeatin and dihydrozeatin promoted secondary root growth, but only at very low concentrations.     

Interaction with ethylene: changing views on the role of abscisic acid in root and shoot growth responses to water stress

Shoot and root growth are differentially sensitive to water stress. Interest in the involvement of hormones in regulating these responses has focused on abscisic acid (ABA) because it accumulates in shoot and root tissues under water-limited conditions, and because it usually inhibits growth when applied to well-watered plants. However, the effects of ABA can differ in stressed and non-stressed plants, and it is therefore advantageous to manipulate endogenous ABA levels under water-stressed conditions. Studies utilizing ABA-deficient mutants and inhibitors of ABA synthesis to decrease endogenous ABA levels, and experimental strategies to circumvent variation in plant water status with ABA deficiency, are changing the view of the role of ABA from the traditional idea that the hormone is generally involved in growth inhibition. In particular, studies of several species indicate that an important role of endogenous ABA is to limit ethylene production, and that as a result of this interaction ABA may often function to maintain rather than inhibit shoot and root growth. Despite early speculation that interaction between these hormones may influence many of the effects of water deficit, this topic has received little attention until recently.     

Relationships between auxin- and acid-induced growth in Vigna radiata hypocotyl segments

The H⁺- and IAA-induced growth responses of isolated Vigna radiata (L.) Wilczek hypocotyl segments were investigated concurrently with IAA-induced H⁺ excretion. The effects of external pH on these reactions were also studied. Experiments were performed with intact, peeled and abraded segments. Only abraded segments reacted to H⁺ and to IAA. In short-term experiments, the cuticle prevented proton efflux and influx; however, it allowed gradual ion movements which become measurable after 1 h. Both phases of the IAA growth response reacted to external pH. The interactions between these two phases and their pH dependencies are discussed.