表油菜素内酯对绿豆上胚轴内源IAA及其氧化酶的影响

用0.5ppm表油菜素内酯处理绿豆幼苗,显著促进上胚轴伸长生长,若切除真叶则可抑制表油菜素内酯诱导的效应。三碘苯甲酸(TIBA)也可抑制表油菜素内酯促进的伸长生长。外源IAA能部分恢复TIBA的抑制效应。经处理的上胚轴内源IAA含量明显高于对照。暗示表油菜素内酯可能通过对内源IAA的调节来促进绿豆上胚轴的伸长生长。 表油菜素内酯处理的绿豆上胚轴组织中,与生长素降解密切相关的IAA氧化酶以及过氧化物酶活性均明显低于对照。     

表油菜素内酯对黄瓜下胚轴伸长、内源GA~3,ABA及淀粉含量的影响

1 ppm表油菜素内酯(epiBR)能显著地促进光下生长的黄瓜下胚轴伸长。其促进伸长的效应需约5h滞后期,明显超过IAA而与GA_3的滞后期接近。GA_3对epiBR促进黄瓜下胚轴的伸长具有增效作用。epiBR能提高内源GA_3,ABA的水平,处理24h后,GA_3/ABA值约为对照的两倍。经epiBR处理后的黄瓜下胚轴内淀粉含量较低,并维持在同一水平,这与GA_3的作用颇为一致。     

表油菜素内酯对油菜幼苗生长及其可溶性糖和蛋白质含量的影响(简报)

表油菜素内酯（epiBR）处理油菜幼苗，可明显促进下胚轴伸长生长，增加子叶面积，同时降低蛋白质含量及子叶中可溶性糖含量。SDS－PAGE检测分白结果表明，epiBR处理后，下胚轴和子叶中的蛋白组分均发生明显的改变。     

表油菜素内酯对绿豆上胚轴核酸代谢的影响

0.5～5 ppm放线菌素D和0.01～0.1ppm亚胺环己酮均能抑制epiBR促进的绿豆上胚轴的生长。DNA、RNA含量测定表明epi—BR处理促进了它们的含量增加。绿豆上胚轴经 epiBR处理48h后,可增强其RNA聚合酶活性(以~H—UTP掺入RNA的DPM计算);DNA和RNA水解酶的活性随着epiBR处理时间的延长而逐渐降低;TIBA则抑制epiBR的上述作用。     

表油菜素内酯对离体黄化小麦叶片展开的影响

油菜甾醇内酯类化合物对叶片展开(leaf-unrolling)的生物活性,以表油菜素内酯效应为最强。epiBR的作用与其浓度及苗龄有关,0.0001ppm时已表现促进作用,至1ppm达最高;epi-BR对4d龄叶片促进最明显,随苗龄增加逐渐下降,表明幼嫩叶片比老叶片对epiBR更为敏感。epiBR能克服环己酰亚胺和放线菌素D对叶片展开的抑制;epiBR与脱落酸之间亦存在拮抗,而与6BA则表现加成作用。     

表油菜素内酯对绿豆幼叶衰老的促进作用

表油菜素内酯（ｅｐｉＢＲ）０．０５ｍｇ／Ｌ能促进绿豆幼叶的衰老,其叶绿素和蛋白质含量均低于对照。绿豆幼叶经ｅｐｉＢＲ处理后,可使过氧化物酶活性明显增加,但同工酶谱无变化;超氧化物歧化酶（ＳＯＤ）和过氧化氢酶（ＣＡＴ）活性随ｅｐｉＢＲ处理时间的延长而降低。ｅｐｉＢＲ能促进丙二醛（ＭＤＡ）含量增加,而其含量与ＳＯＤ和ＣＡＴ活性呈显著负相关。     

油菜素甾酮的~（125）I标记及其生物活性

油菜素甾酮（ｂｒａｓｓｉｎｏｓｔｅｒｏｎｅ）是合成油菜素内酯（ｂｒａｓｓｉｎｏｌｉｄｅ）的前体,它具有７０％以上的油菜素内酯生物活性。油菜素甾酮的Ｂ环－６－酮基经与盐酸羧甲基羟胺反应后得到油菜素甾肟,当浓度为１０μｍｏｌ／Ｌ时用水稻叶片倾斜法测得其生物活性比对照增加６０％以上;当浓度为２μｍｏｌ／Ｌ时能促使黄瓜下胚轴伸长,比对照增加２０％。用油菜素甾肟与油菜素内酯或油菜素甾酮一起处理黄化水稻幼苗,测得水稻叶片与叶路之间的倾斜角度介于它们单独处理之间。用氯胺－Ｔ法制备１２５Ｉ－组胺,再与油菜素甾肟结合。先用黄瓜幼苗下胚轴伸长法初步筛选活性组份,再用水稻叶片倾斜法鉴定活性,表明Ｒｆ０．９３处的组份能使水稻幼苗叶片的倾斜活性增加２５％,其放射性比强为７３．８ＧＢｑ／ｍｍｏｌ。     

油菜素甾酮的^125I标记及其生物活性

油菜素甾酮是合成油菜素内酯的前体,它具有７０％以上的油菜素内酯生物活性。油菜素甾酮的Ｂ环－６－酮基经与盐酸羧甲基羟胺反应后得到油菜素甾肟,当浓度为１０μｍｏｌ／Ｌ时用水稻叶片倾斜法其生物活性比对照增加６０％以上;当浓度为２μｍｏｌ／Ｌ时能促使黄瓜下胚轴伸长,比对照增加２０％。用油菜素甾肟与油菜素内酯或油菜素甾酮一起处理黄化水稻幼苗,测得水稻叶片与叶鞘之间的倾斜角度介于它们单独处理之间。用氯胺－Ｔ法     

表油菜素内酯对绿豆下胚轴切段的保幼延衰作用

表油菜素内酯(1ppm)对绿豆下胚轴切段有明显的保幼延衰和维持旺盛伸长生长的作用。0.1～1ppm的表油菜素内醋几乎完全阻抑了绿豆下胚轴切段花青素的累积。 表油菜素内醋处理的下胚轴能维持远较对照为高的呼吸作用和蛋白质合成水平。电镜观察表明,表油菜素内酯处理5日后的离体下胚轴切段细胞仍然保持完整的细胞器结构,而对照细胞内部完整细胞器结构则已崩溃破坏殆尽。     

表油菜素内酯对月季切花保鲜作用的研究

本文初步探讨了表油菜素内酯（epiBR）对瓶插月季切花的保鲜作用。与对照（蒸馏水）和基本液（2％蔗糖＋500mgL-1柠檬酸＋250mgL-8-羟基喹啉＋25mgAgNO3）相比,经epiBR处理（基本液＋0．1mgL-1epiBR）的月季切花花枝坚挺,蓝变延迟,瓶插寿命延长1-1.5倍。测定有关生理指标表明,epiBR处理对月季切花瓶插花枝前期鲜重的增加及后期的保持有明显作用。并显著延缓花瓣和叶片质膜相对透性的增加,还能使瓶插前期花瓣还原糖含量增加。epiBR处理对花瓣蛋白质和叶片叶绿素含量变化无明显影响,而对花瓣花青素水平下降有轻微的促进作用。     

Effect of epibrassinolide on hypocotyl growth of the tomato mutant diageotropica

The effect of epibrassinolide (epiBR) on the growth and gravitropism of hypocotyls was investigated in diageotropica (dgt), a mutant of tomato (Lycopersicon esculentum Mill.). The elongation of (dgt) hypocotyls, which had been reported to be auxin-insensitive, was promoted by increasing concentrations of indole-3-acetic acid (IAA) in the presence of epiBR. α-(p-Chlorophenoxy)isobutyric acid, an inhibitor of auxin action, blocked the enhancement of growth by IAA and epiBR. Time course analysis of IAA-induced dgt hypocotyl elongation in the presence of epiBR revealed typical auxin response kinetics. These results suggest that epiBR restores the auxin responsiveness of dgt hypocotyls with respect to elongation. However, epiBR did not rescue the dgt phenotype with respect to shoot gravitropism. It was therefore concluded that brassinosteroid insensitivity or deficiency is not the primary defect of the dgt mutation. Received: 23 January 1998 / Accepted: 20 June 1998     

Levels of Indol-3yl-acetic acid (IAA), IAA-oxidase and Peroxidase in Developing Cucumber Seedlings

The level of indol-3yl-acetic acid (IAA) in the cotyledons of cucumber seedlings increases in the period 4 to 11 days after germination. In hypocotyls and roots the IAA level decreases. IAA-oxidase activity of homogenates of cotyledons, hypocotyls and roots decreases with age. The soluble fraction of all three organs contains an IAA-oxidase, which may be allosteric. It is suggested that this IAA oxidase limits the upper level of IAA in the cell. The cell wall fraction of the three organs contains IAA-oxidases with conventional kinetics. The function of this IAA oxidase is probably to degrade exogenous IAA.     

Effect of light on peroxidase and lignin synthesis in mungbean hypocotyls

Two days of light irradiance reduced the growth of mungbean hypocotyls as well as the levels of endogenous indole-3-acetic acid (IAA). In hypocotyls, both peroxidase and laccase activities were enhanced by light. The lignin content in mungbean hypocotyls was enhanced twofold by light. The inhibition of mungbean hypocotyl growth caused by light might be due to the decline of endogenous IAA, which could be degraded by a cationic peroxidase. The higher levels of lignin were correlated with the increased anionic peroxidase activity in light-treated tissues.     

Induction of peroxidases in cucumber hypocotyls by wounding and fungal infection

The induction of peroxidases (EC 1.11.1.7) during elicitation of lignification by α-1,4-linked oligogalacturonides in cucumber hypocotyl segments ( Cucumis sativus L. cv, Wisconsin SMR 58) was investigated. The wounding associated with the preparation of hypocotyl segments induced a 19-fold increase in peroxidase activity during the following 72 h. The increase was partially due to an increase in activity of a constitutive peroxidase with a pI of 8.9 and partially due to the expression of new peroxidase isozymes with pIs of 3.8, 5.4, 6.2, 9.1 and 9.4. The oligogalacturonides did not induce any peroxidase activity in addition to the wound-induced activity. These results suggest that either the constitutive peroxidase isozyme (pI 8.9) of intact hypocotyls or some of the wound-induced peroxidases are involved in the oligogalacturonide-induced lignification.
Induction of the peroxidases by wounding was inhibited by cycloheximide. This indicates that they accumulate as a result of de novo protein synthesis. Actinomycin D caused only a modest inhibition of the wound-induction peroxidases, indicating that the process is regulated at the level of translation.
Peroxidase activity increased more rapidly in resistant than in susceptible cucumber hypocotyls after inoculation with the pathogen Cladosporium cucumerinum Ellis & Arthur. The pattern of isozymes which was induced by fungal infection of resistant hypocotyls was similar to the pattern of isozymes induced by wounding. This suggests that similar induction mechanisms may be involved in the two processes.     

Calcium and calcium-dependent protein kinases are involved in nitric oxide- and auxin-induced adventitious root formation in cucumber

A few years ago it was demonstrated that nitric oxide (NO) and cGMP are involved in the auxin response during adventitious root (AR) formation in cucumber (Cucumis sativus). More recently, a mitogen-activated protein kinase cascade was shown to be induced by IAA in a NO-dependent, but cGMP-independent, pathway. In the present study, the involvement of Ca2+ and the regulation of Ca2+-dependent protein kinase (CDPK) activity during IAA- and NO-induced AR formation was evaluated in cucumber explants. The effectiveness of several broad-spectrum Ca2+ channel inhibitors and Ca2+ chelators in affecting AR formation induced by IAA or NO was also examined. Results indicate that the explants response to IAA and NO depends on the availability of both intracellular and extracellular Ca2+ pools. Protein extracts from cucumber hypocotyls were assayed for CDPK activity by using histone IIIS or syntide 2 as substrates for in-gel or in vitro assays, respectively. The activity of a 50 kDa CDPK was detected after 1 d of either NO or IAA treatments and it extended up to the third day of treatment. This CDPK activity was affected in both extracts from NO- and IAA-treated explants in the presence of the specific NO-scavenger cPTIO, suggesting that NO is required for its maximal and sustained activity. The in-gel and the in vitro CDPK activity, as well as the NO- or IAA-induced AR formation, were inhibited by calmodulin antagonists. Furthermore, the induction of CDPK activity by NO and IAA was shown to be reliant on the activity of the enzyme guanylate cyclase.     

The effect of 4-chlororesorcinol on the endogenous levels of IAA,ABA and oxidative enzymes in cuttings

Treatment of bean cuttings with 4-chlororesorcinol (4-CR), known to increase the number of roots and extend their distribution, prevented the accumulation of free indol-3-yl-acetic acid (IAA) in the hypocotyls within 24 h after cutting preparation. In mung bean there was no change in the distribution (upper half vs. 1 ower half of the hypocotyl) of IAA within the hypocotyl as a result of the treatment. In bean cuttings the treatment with 4-CR prevented the accumulation of IAA in the bottom of the cutting. Oxidation of IAA as a measure of IAA oxidase activity in bean was enhanced appreciably by 4-chlororesorcinol. The level of abscisic acid in mung bean, on the other hand, remained 3–4 fold higher than in the control, yet still about 50% lower than the zero time level. In untreated mung bean cuttings the activity of peroxidase increased after cutting preparation. In contrast, the activity of peroxidase in 4-Cr-treated cuttings was consistently lower. In order to relate to the effect of exogenously applied auxin the level of peroxidase was measured also in indol-3-yl-butyric acid-treated cuttings. The overall peroxidase activity in IBA-treated cuttings was not affected. However, when assaying for the different isozymes the drop in peroxidase activity was most evident in the inducible basic isoperoxidases both in 4-CR and IBA treatments. It appears that the exposure to 4-CR exerts an effect that is similar to that of exogenously applied auxin, affecting the activity of basic peroxidases and enhancing the oxidation of endogenous IAA, thus allowing the organization of the primordia.Abbreviations ABA - abscisic acid - 4-CR - 4-chlororesorcinol - IAA - indol-3-yl-acetic acid - IBA - indol-3-yl-butyric acid     

Tryptophan Decarboxylase Activity in Developing Cucumber Seedlings

The rate of decarboxylation of DL-tryptophan-carboxyl-¹⁴C in homogenates of cotyledons, hypocotyls and roots of sterile and non-sterile cucumber seedlings of 4, 8 and 11 days was measured. Tryptophan decarboxylating activity is highest in hypocotyls, lowest in cotyledons. In all organs the activity decreases with age. This enzyme activity does not parallel the IAA level in the organs during ageing.     

Changes in Paramagnetic Manganese (Mn2+) and Related Enzyme Activities in Isolated Cucumber Cotyledons During Growth: II. EFFECT OF 6-FURFURYLAMINOPURINE

Changes in the activities of IAA oxidase, peroxidase, ascorbicacid utilization (AAU), and in the level of paramagnetic manganese(Mn²⁺) have been studied during kinetin-induced growth of theisolated cucumber cotyledons in light or in dark. In kinetin-treatedcotyledons exposed to light, inhibition in the level of paramagneticmanganese corresponds with an enhancement in IAA oxidase activity.The level of paramagnetic manganese shows an inverse correlationwith IAA oxidase activity. In darkness the level of Mn²⁺ doesnot show the same correlation with IAA oxidase activity as inthe light. Kinetin stimulates peroxidase activity both in thelight and in darkness. Enhancement of IAA oxidase activity andno corresponding change in the level of paramagnetic manganeseindicates that the oxidation of IAA in dark-grown, kinetin-treatedcotyledons is brought about by peroxidase. It appears that thephenolic cofactors required for the oxidation of manganese andIAA may be limiting in kinetin-treated cotyledons in darkness.Thus in the light, IAA oxidation seems to be brought about byperoxidase as well as manganese, whereas in darkness it is mediatedby peroxidase alone. Increase in IAA oxidase activity duringkinetin-induced growth of the isolated cotyledons is incompatiblewith the idea that increased IAA oxidase activity would limitthe availability of auxin for growth. Kinetin does not mimicthe action of light on IAA oxidase activity; on the contrary,it removes the inhibitory effect of light on IAA oxidase activityprobably through the synthesis of IAA oxidase activators.     

DIFFERENT SPECIES,SUCROSE, AND LIGHT IN PLANT SECTION ELONGATION TESTS

Sections from both dark- and light-grown seedlings of 11 species were used to test responses to IAA (indoleacetic acid), sucrose, and an inhibitor prepared from cabbage seedlings. Variability among species was great; however, results indicate that many species, light-grown as well as dark-grown, could prove useful in bioassays and probably should be investigated. Although elongation of segments from high-intensity-light-grown cabbage and cucumber hypocotyls and oat coleoptiles had essentially stopped by the time of cutting, their growth and response to IAA as sections were considerable. Neither oat coleoptile nor pea internode sections can be considered representative because of differences in responses to sucrose, of dark-grown sections to light, and to an inhibitor prepared from cabbage. Sucrose generally did not stimulate and even inhibited response of most hypocotyls to IAA. Sucrose was absorbed by sections, increasing final dry weight while not affecting elongation. Sucrose reduced the rate of respiratory decay in cabbage and sunflower, but IAA did not affect respiration. Changes in length and fresh weight of cucumber hypocotyl sections were comparable.