胆固醇和脱落酸对棉苗抗寒力的影响

一、前言低温降低膜的流动性,并损伤细胞表面膜(质膜)上酶的活性(如ATP酶),是造成低温伤害的关键。由于生物膜的流动性与其结构功能密切相关。因而植物抗寒力与其在低温下能否保持膜的流动性和稳定性有关。胆固醇能稳定膜结构,并提高植物细胞对低温的抵抗力。     

干旱和淹水对棉苗某些生理特性的影响

以转Bt基因抗虫棉33B为材料,通过控制苗期土壤水分含量,研究了干旱和淹水对棉苗若干生理特性的影响。结果表明,干旱和淹水皆抑制棉苗株高增长、叶片扩展和干物质积累,明显降低叶片的净光合速率(Pn),促进叶片细胞膜脂过氧化,MDA含量增加,K^ 吸收受抑,功能叶和顶尖代谢活动最旺盛部位的K^ 含量降低。但干旱对地上部生长的影响大于淹水,而淹水对根系生长的影响又大于干旱;淹水处理的棉苗在儿11:00～14：00仍能维持相对较高的净光合速率(Pn),而此时干旱棉苗的Pn却显著降低。     

棉麦两熟共生期遮荫对棉苗生长发育的影响

黄淮棉区棉麦两熟2号主要种植方式（3：2式和3：1式）共生期不同程度遮荫,影响棉苗叶片C、N代谢和可溶性蛋白质含量,过氧化物酶（POD）活性、丙二醛（MDA）累积,与一熟棉相比较,遮荫棉苗的生理代谢能力降低,但3：2式共生期遮荫对棉苗生理代谢及其生长发育的影响与一熟棉差异较小,3：1式共生期遮荫对棉苗的生理代谢影响较大,不利于棉苗生长发育。     

寄主植物对昆虫抗寒力的影响

寄主植物是影响昆虫抗寒力的重要因素之一.本文综述了寄主植物对昆虫越冬虫态的发育进度及抗寒物质的积累、抗冻蛋白、冰核物质的形成、虫体含水量等方面的影响.分析了目前研究寄主植物对昆虫抗寒力影响中存在的问题及今后的研究方向.     

棉苗的病害

一.棉苗病害的种类及其特征棉病的种类很多,在我国已发生的有30余种,其中常见的约20余种。仅在苗期经常发生且较普遍和严重的有下列7种: (1) 立枯病由半知菌纲Rhizoctonia solani真菌侵害所致。幼根和茎基部先发生凹陷褐色斑块,以后扩大、腐烂,色亦加深;拔出时,患处有菌丝黏附着小土块,风吹摇动;严重受害者,子叶萎垂,幼茎倒伏而死。 (2)猝倒病由藻状菌纲Pythium aphanidermatum真菌为害所致。幼苗根部得病后先呈黄色水肿状,迅即变软、腐烂,色亦转深,但患部不如立枯病的凹黑,促成倒苗极快。     

棉铃虫取食转Bt棉后蛹的抗寒力测定

在棉铃虫HelicoverpaarmigeraH櫣bner人工饲料中分别添加转Bt基因棉叶粉和常规棉叶粉饲喂幼虫,经滞育诱导后,发现2个处理间棉铃虫蛹的滞育率相似,2个处理间滞育蛹的自由水和结合水含量没有差异;但取食含Bt棉叶粉人工饲料的棉铃虫滞育蛹的过冷却点和结冰点显著高于对照组,蛹重及与抗寒性有关的脂肪和糖原含量均显著低于对照组。     

钙对盐胁迫下棉苗离子吸收分配的影响

研究了钙对NaCl胁迫下棉花幼苗体内离子分布的影响及其与根系质膜H^ -ATP酶、液泡膜H^ -dATP酶和H^ -PP酶活性的关系。不同器官离子含量和根系横切面X-射线微区分析结果表明,NaCl胁迫下外源钙明显减少棉花幼苗对Na^ 的吸收及其向茎杆、叶片的运输,增加对K^ 和Ca^2 的吸收及其向茎相杆、叶片的运输,增强棉苗体内的盐分区域化分配,提高根冠比和干物质积累,根系电解质渗漏率下降,钙明显提高盐胁迫下幼根细胞质膜H^ -ATP酶、液泡膜H^ -ATP酶和H^ -PP酶的活性,与钙调节棉花对离子的吸收、分配相一致,说明这些酶可以为根细胞中的Na^ 在液泡中积累以及K^ 、Ca^2 的选择性吸收和运输提供动力。     

钙对盐胁迫下棉苗离子吸收分配的影响

研究了钙对NaCl胁迫下棉花幼苗体内离子分布的影响及其与根系质膜H+-ATP酶、液泡膜H+-ATP酶和H+-PP酶活性的关系。不同器官离子含量和根系横切面X-射线微区分析结果表明,NaCl胁迫下外源钙明显减少棉花幼苗对Na+的吸收及其向茎杆、叶片的运输,增加对K+和Ca2+的吸收及其向茎杆、叶片的运输,增强棉苗体内的盐分区域化分配,提高根冠比和干物质积累,根系电解质渗漏率下降。钙明显提高盐胁迫下幼根细胞质膜H+-ATP酶、液泡膜H+-ATP酶和H+-PP酶的活性,与钙调节棉花对离子的吸收、分配相一致,说明这些酶可以为根细胞中的Na+在液泡中积累以及K+、Ca2+的选择性吸收和运输提供动力。     

脱落酸对植物抗逆性影响的研究进展

脱落酸（ABA）是一种重要的植物激素,受到生物胁迫和非生物胁迫的调控,在植物对胁迫环境抗逆性中发挥重要作用。综述了近些年来国内外有关ABA生理功能抗逆性研究的一些最新进展,重点介绍ABA在植物干旱、高盐、低温、病虫害等逆境胁迫反应中起重要作用,在植物保护和农林业生产中的应用有重要意义。     

脱落酸对黄连体细胞胚胎发育的影响

用ＨＰＬＣ法测得黄连体细胞胚的内源ＡＢＡ含量,在胚性细胞团、球形胚、鱼雷形胚和子叶胚中分别为０．４５２、０．４６１、０．８３１和２．５０μｇ／ｇ ｆｒ．ｗｔ。培养基中加入４μｍｏｌ／Ｌ ＡＢ时,可最大幅度地提高正常子叶胚的和次生胚的产量,环己亚胺对体细胞胚（子叶胚）蛋白质合成的抑制率在含ＡＢＡ的培养基上显著高于不含ＡＢＡ的培养。由此推测,ＡＢＡ调节黄连体细胞胚发育的方式之一是诱导蛋白质合成。     

Involvement of Abscisic Acid in Ethylene-Induced Cotyledon Abscission in Cotton Seedlings

Cotton (Gossypium hirsutum L. cv LG102) seedlings raised from seeds exposed to 100 [mu]M norflurazon (NFZ) during imbibition contained reduced levels of free abscisic acid (ABA) and were visibly achlorophyllous. Exposure of untreated cotton seedlings to ethylene concentrations >1 [mu]L/L for 24 h resulted in cotyledon abscission. In contrast, exposure of NFZ-treated seedlings to concentrations of ethylene [less than or equal to]50 [mu]L/L elicited no cotyledon abscission. Application of ABA, an ABA analog, or jasmonic acid to NFZ-treated seedlings restored ethylene-induced abscission. Isolated cotyledonary node explants prepared from NFZ-treated seedlings exhibited an altered dose-response pattern of ethylene-induced petiole abscission. Endogenous levels of free IAA were unaltered in NFZ-treated seedlings. Ethylene treatment (50 [mu]L/L, 24 h) had no effect on free indoleacetic acid (IAA) levels in either control or NFZ-treated seedlings. Levels of conjugated (ester plus amide) IAA were substantially increased in NFZ-treated seedlings regardless of ethylene treatment. These results indicate that endogenous ABA plays an essential, but physiologically undefined, role in ethylene-induced cotyledon abscission in cotton.     

Movement and Endogenous Levels of Abscisic Acid during Water-Stress-induced Abscission in Cotton Seedlings

In an effort to investigate possible involvement of abscisic acid (ABA) in foliar abscission processes, its movement and endogenous levels were examined in cotyledons taken from cotton seedlings (Gossypium hirsutum L.) subjected to varying degrees of water deficit, a condition which initiates leaf abscission. Using a pulse-labeling technique to avoid complications of uptake and exit from the tissue, ABA-1-¹⁴C movement was observed in both basipetal and acropetal directions in cotyledonary petioles taken from well watered, stressed, and rewatered plants. The label distribution patterns obtained after 1 and 3 hours of transport under all situations of water supply were diffusive in nature and did not change when tested under anaerobic conditions. The transport capacity of the petioles ranged from 3.6 to 14.4% ABA-1-¹⁴C transported per hour at estimated velocities of 0 to 2 millimeters per hour. Comparison of basipetal and acropetal movement indicated a lack of polarity under all conditions tested. These low transport capacities and slow velocities of movement, when compared to the active transport systems associated with auxin movement, as well as the lack of anaerobic effects and polarity, suggest that ABA movement in cotton cotyledonary petiole sections is facilitated by passive diffusion. Increases in free and bound ABA in the lamina with increased water stress did not correlate with patterns of cotyledonary abscission. Thus, no evidence was found to suggest that ABA is directly involved in stress-induced abscission processes.     

外源脱落酸对小麦幼苗抗镉胁迫能力的影响

以小麦(Triticum aestivum L.)为试材,采用水培法研究了100mg/L镉(Cd2+)胁迫条件下施用外源脱落酸(ABA)对小麦幼苗生长及某些生理生化指标的影响。结果表明:(1)100mg/L Cd2+胁迫下,小麦叶片膜脂过氧化产物丙二醛(MDA)含量显著提高,植株生长受到抑制;(2)外源ABA能够明显提高Cd2+胁迫小麦幼苗的根系活力,增加其叶片SOD、CAT和POD活性,促进其脯氨酸积累,降低MDA的含量,并以5.0μmol/L ABA的效果最明显;(3)1.0～5.0μmol/L外源ABA不同程度地缓解Cd2+胁迫对小麦幼苗生长的抑制作用,且5.0μmol/L时效果最明显,其株高、根长、总干重分别比单一Cd2+胁迫处理显著提高6.73%、149%和10.52%,而10.0μmol/LABA反而加重了Cd2+对小麦幼苗生长的伤害。因此,适宜浓度的外源ABA能够通过增加体内保护酶活性和脯氨酸含量来缓解Cd2+胁迫对小麦幼苗生长的抑制作用,增强小麦幼苗的抗Cd2+胁迫能力,并以5.0μmol/L ABA处理效果最好。     

Plant Cold Acclimation: The Role of Abscisic Acid

The freezing tolerance or cold acclimation of plants is enhanced over a period of time by temperatures below 10°C and by a short photoperiod in certain species of trees and grasses. During this process, freezing tolerance increases 2–8°C in spring annuals, 10–30°C in winter annuals, and 20–200°C in tree species. Gene upregulation and downregulation have been demonstrated to be involved in response to environmental cues such as low temperature. Evidence suggests ABA can substitute for the low temperature stimulus, provided there is also an adequate supply of sugars. Evidence also suggests there may be ABA-dependent and ABA-independent pathways involved in the acclimation process. This review summarizes the role of ABA in cold acclimation from both a historical and recent perspective. It is concluded that it is highly unlikely that ABA regulates all the genes associated with cold acclimation; however, it definitely regulates many of the genes associated with an increase in freezing tolerance.     

Amelioration of Chilling Injuries in Cucumber Seedlings by Abscisic Acid

Exposure of cucumber seedlings (Cucumis sativus L.) to chilling temperature resulted in injuries such as increased leakage of cellular materials, loss of water and wilting. In addition, the development of the seedlings after the exposure to chilling was impaired. Abscisic acid applied to the seedlings prior to chilling significantly ameliorated these injuries.     

Potential Role of Abscisic Acid in Cotton Fiber and Ovule Development

Fibers and ovules of a cotton cultivar (Gossypium hirsutum L. Trambak-108) were analyzed for growth and free abscisic acid (ABA) content by indirect enzyme immunoassay. An inverse correlation between fiber elongation and ABA content was observed. In the seed, accumulation of ABA was observed during secondary thickening and the maturation phase. The potential role of ABA in fiber and seed development is discussed. Received June 25, 1997; accepted October 15, 1997     

Effect of Abscisic Acid and Other Plant Hormones on Growth of Apical and Lateral Buds of Seedlings

The effect of abscisic acid (AbA) on the growth of lateral and apical buds was studied in seedlings of Pisum sativum and some other species. The hormone was applied in three different ways: 1) directly to the lateral bud on the second node of decapitated pea seedlings as 5 μI droplets in an ethanolic solution; 2) to the cut surface of decapitated seedlings: 3) to the apical bud of intact plants. AbA directly applied in amounts of 5 to 0.1 μg to the lateral bud of the second node of decapitated seedlings had a strong inhibitory effect on the bud. Application to the cut surface of seedlings decapitated about 5 mm above the second node resulted in slight inhibition of the lateral bud on the second node and in growth promotion of the bud on the first node. When AbA at 10 to 0.1 μg was applied to the apical bud of intact seedlings, the growth of this bud was inhibited but the lateral buds grew out. It is concluded that the release of the lateral buds from apícal dominance is the result of the inhibitory effect of AbA on growth of the apical bud and of low transport of AbA. This conclusion is supported by application of GA₃ and IAA, individually and each combined with AbA.     

Longitudinal Gradients of Indole-3-Acetic Acid and Abscisic Acid in the Hypocotyl of Etiolated Bean Seedlings

The longitudinal distribution of abscisic acid (ABA) and indole-3-aceticacid (IAA) along the hypocotyl of 5-d-old etiolated Phaseolusvulgaris L. cv. Limburg seedlings was measured. IAA was analysedby the L-methyl-indole--pryone assay (2-MIP) and ABA by electroncapture gas chromatography (ECD-GC). Length and width of theinner parenchyma cells, growth rate and protein content werealso measured. Cell expansion occurred predominantly in a region20 mm below the centre of the hook where elongation rate wasmaximal and where protein concentration decreased rapidly withdistance from the hook. The ratio between ABA and IAA was constant along the lengthof the hypocotyl. On a fresh weight basis the concentrationof both growth substances was maximal in the upper (youngest)part, decreased in slightly older sections where cell expansionwas proceeding and was smallest in the basal regions where cellexpansion was complete. However, when expressed on a proteinbasis the concentration gradient of the hormones was the reverseof that described on a fresh weight basis. Key words: IAA, ABA, hypocotyl, etiolated, bean     

Regulation of Water Deficit-Induced Abscisic Acid Accumulation by Apoplastic Ascorbic Acid in Maize Seedlings

Water deficit-induced abscisic acid （ABA） accumulation is one of the most important stress signaling pathways in plant cells. Redox regulation of cellular signaling has currently attracted particular attention, but much less is known about its roles and mechanisms in plant signaling. Herein, we report that water deficit-induced ABA accumulation could be regulated by ascorbic acid （AA）-controlled redox status in leave apoplast. The AA content in non-stressed leaves was approximately 3 umol/g FW, corresponding to a mean concentration of 3 mmol/L in a whole cell. Because AA is mainly localized in the cytosol and chloroplasts, the volume of which is much smaller than that of the whole cell, AA content in cytosolic and chloroplast compartments should be much higher than 3 mmol/L. Water deficit-induced ABA accumulation in both leaf and root tissues of maize seedlings was significantly inhibited by AA and reduced glutathione （GSH） at concentrations of 500 umol/L and was completely blocked by 50 mmol/L AA and GSH. These results suggest that the AA-induced inhibition of ABA accumulation should not occur at sites where AA exists in high concentrations. Although water deficit led to a small increase in the dehydroascorbic acid （DHA） content, no significant changes in AA content were observed in either leaf or root tissues. When compared with the whole leaf cell, the AA content in the apoplastic compartment was much lower （i.e. approximately 70 nmol/g FW, corresponding to 0.7 mmol/L）. Water deficit induced a significant decrease （approximately 2.5-fold） in the AA content and an increase （approximately 3.4-fold） in the DHA content in the apoplastic compartment, thus leading to a considerably decreased redox status there, which may have contributed to the relief of AA-induced inhibition of ABA accumulation, alternatively, promoting water deficit-induced ABA accumulation. Reactive oxygen species （ROS） could not mimic water deficit in inducing ABA accumulation, suggesting that the inhibition of ABA accumulation by AA or GSH was not related to their ROS-scavenging ability. The results of the present study suggest that the redox status in the apoplastic compartment, as determined by AA and DHA, may play a vital role in the regulation of the signaling process for water deficit-induced ABA accumulation.