The Effect of Local Cooling of Cucumber and Wheat Seedlings on Various Kinds of Stress Resistance of Their Leaves and Roots

Shoots and roots of wheat (Triticum aestivum L., cold-resistant species) and cucumber (Cucumis sativus L., cold-sensitive species) were chilled at 2°C or 10°C, respectively, for 7 h. The changes in cold, heat, and salt resistance in treated leaf and root cells were recorded. Local cooling of the leaf resulted in an increase of its cold and salt tolerance, but its heat tolerance remained unchanged. At the same time, cold tolerance of the root slightly increased as a result of local cooling, but its heat and salt tolerance decreased. Cooling of the shoot did not affect the cold and heat tolerance of root cells but caused a decrease in their salt tolerance. Finally, in the leaf maintained at a normal temperature, there was an increase in all kinds of stress resistance as a result of root cooling. We discuss the possibility of an unspecific change in stress resistance caused by metabolic shifts. These shifts are induced by a signal, which is transmitted inside the plant into plant organs located at a considerable distance from the chilled ones.     

Changes in the Levels of IAA and ABA in Cucumber Leaves under Progressive Soil Drought

Changes in the IAA and ABA contents in cucumber (Cucumis sativus L.) leaves during adaptation to drought were studied. An increase in the water-retaining capacity and heat resistance of leaves indicating the onset of adaptation occurred when the leaf growth has been already suppressed. There was a transient increase in the ABA content during the initial stage of adaptation. An increased IAA content was maintained for a longer period, throughout about two-third of the adaptation period. A second increase in the ABA content was observed before the onset of leaf permanent wilting, when IAA content already decreased. Our data suggest that not only ABA, but also IAA are involved in the development of defense responses during the adaptation to drought.     

Effects of Calcium and Lanthanum on ABA Biosynthesis in Cucumber Leaves

Cucumber (Cucumis sativus L.) leaves were treated with CaCl₂ and LaCl₃ at concentrations of 0.002, 0.02, 0.04, 0.2, 0.4, and 2.0 mM to study the effects of calcium and lanthanum on plants, especially on the pathway of abscisic acid biosynthesis. The activity of lipoxygenase (Lox) was measured, and the contents of violaxanthin (Vio, a precursor to ABA) and ABA were estimated. In addition, the soluble proteins in treated leaves were analyzed. The results suggest that La³⁺ influences Lox activity and the contents of Vio and ABA. Their changes are correlated to one another, thus indicating that ABA can be derived from a carotenoid in the presence of lanthanum. After leaf treatments with ions, the content of soluble proteins changed and a 41 kD polypeptide appeared confirming responsive gene expression. The effects of both ions on ABA and protein biosyntheses suggest that the appearance of this protein is not related to the endogenous ABA levels.     

The Development of Leaf Heat-Tolerance during the Local Heating of Seedling Organs

Experiments using cucumber (Cucumis sativusL.), wheat (Triticum aestivumL.), and barley (Hordeum vulgareL.) seedlings showed that actinomycin D partially inhibited an increase in the heat-tolerance of leaves heated at 38°C for 7 h but did not affect this index when the roots were heated. Exogenous ABA increased heat-tolerance in both cases. These results, with regard to the data demonstrating an important contribution of protein synthesis to the specific increase in heat-tolerance during the heat acclimation of intact plants, make it possible to conclude that the development of leaf heat-tolerance resulting from the local heating of shoots depends on the induced synthesis of mRNAs and respective proteins. At the same time, there is little or no such dependence during root heating. ABA manifested itself as a factor of a general, nonspecific increase in heat-tolerance during the local heating of both shoots and roots.     

Effect of Enhanced UV-B Radiation on Polyamine Content and Membrane Permeability in Cucumber Leaves

Cucumber plants (Cucumis sativus L., cv. Jingchun 3) were grown in a greenhouse under PAR illumination of 400–600 mol/(m² s) at 30/15°C (day/night) temperature. Two enhanced biologically effective UV-B radiation levels per day were applied: 8.82 kJ/m² (T₁) and 12.6 kJ/m² (T₂). Cucumber seedlings were irradiated 7 h per day for 25 days under T₁ and T₂. A comparative study of growth, membrane permeability, and polyamine content in cucumber leaves under T₁ and T₂ treatments was conducted. UV-B radiation resulted in the dose-dependent decrease in leaf area, dry weight of foliage, and plant height. The T₁ and T₂ treatments caused an increase in the contents of putrescine, spermine, and spermidine. However, the total polyamine content declined slightly when electrolyte leakage increased dramatically on the 18th day of treatment, especially after T₂ treatment. It can be concluded that polyamine accumulation in the cucumber leaves is an adaptive mechanism to the stress caused by UV-B radiation.     

不同水分处理对日光温室黄瓜多胺与激素的影响

研究了不同土壤含水量对日光温室黄瓜生长与物质代谢的影响 ,结果如下 :冬春茬各生育期随着土壤水分的减少 ,不同处理的叶片数、叶面积、株高、节间长均降低。水分亏缺初期 ,叶片脯氨酸含量随着土壤含水量的降低而增加 ,随着时间延长此趋势消失。盛瓜期 Pro含量以 T1最多 ,达 17.95 μg/ g DW,分别是 T2与 T3的 2 .0倍与 2 .4倍 ;末瓜期各处理的 Pro含量均达最高值 ,T1、T2、T3分别为 2 5 .30、15 .6 0、12 .33μg/ g DW,秋冬茬叶片脯氨酸含量变化规律同冬春茬 .无论冬春茬还是秋冬茬 ,游离蛋白质的变化规律同脯氨酸。叶片亚精胺 (Spd)与腐胺 (Put)含量随着土壤水分的减少而增加。不同水分处理对黄瓜叶片精胺(Spm)含量的影响不大。根系中 Spd、Put、Spm的变化趋势同叶片。冬春茬不同水分处理的黄瓜叶片 ABA含量均随着土壤含水量的减少而增加     

Effects of La<Superscript>3+</Superscript> on the Active Oxygen-Scavenging Enzyme Activities in Cucumber Seedling Leaves

The effects of La³⁺ on the antioxidant enzyme activities and the relative indices of cellular damage in cucumber seedling leaves were studied. When cucumber seedlings were treated with low concentrations of LaCl₃ (0.002 and 0.02 mM), peroxidase (PO) activity increased, and catalase (CAT) activity was similar to that of control leaves at 0.002 mM La³⁺ and increased at 0.02 mM La³⁺, whereas superoxide dismutase (SOD) activity did not change significantly. The increase in the contents of chlorophyll (including chlorophylls a and b), carotenoids in parallel with the decrease in the level of malondialdehyde (MDA) suggested that low concentration of La³⁺ promoted plant growth. However, except the increase in SOD activity at 2 mM La³⁺, CAT and PO activities and the contents of pigments decreased at high concentrations of La³⁺ (0.2 and 2 mM), leading to the increase of MDA content and the inhibition of plant growth. It is suggested that lanthanum ion is involved in the regulation of active oxygen-scavenging enzyme activities during plant growth.__________From Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 338–342.Original English Text Copyright © 2005 by Shi, Chen, Huang.This article was submitted by the authors in English.     

部分根系供磷对黄瓜根系和幼苗生长及根系酸性磷酸酶活性影响

通过分根处理研究了部分根系供磷对黄瓜幼苗生长、植株体内的含磷量及根系酸性磷酸酶活性的影响。结果表明 ,2 0 %根系缺磷 (1条根缺磷 ,4条根供磷 )可以促进根系及植株地上部的生长 ,其根系及地上部的生物量分别是正常生长植株的 1.39倍和 1.2 1倍。2 0 %根系缺磷 ,还可以促进其它供磷根系对磷的吸收。分根处理后 ,2 0 %根系缺磷不影响植物对磷营养的需要 ,但却表现出了R/S比增大的典型缺磷反应 ,说明植物感应缺磷根系起着比地上部更为重要的作用。分根处理后不供磷根系的酸性磷酸酶活性显著高于供磷根系的酸性磷酸酶活性 ,并且根系的酸性磷酸酶活性只与根系的含磷量显著相关 ,与地上部的磷营养状况关系不明显。这说明 ,缺磷条件下 ,黄瓜植株根系分泌酸性磷酸酶活性的增高 ,是黄瓜根系对低磷胁迫的适应性机理 ,而不是地上部改善体内磷营养的调控机理。     

黄瓜的冷害及耐冷性

随着蔬菜反季节栽培面积的不断扩大,如何提高黄瓜(Cucumis sativus L.)耐冷性已成为选育新品种的研究重点.系统地综述近几年黄瓜耐冷性的鉴定、获得途径、冷害机理以及遗传和分子遗传学等方面的研究,以促进对黄瓜冷害机制的研究,加速耐冷品种的培育.耐冷性鉴定时要从耐冷指数、低温发芽能力、MDA(丙二醛)含量和电解质渗漏率等几个方面综合鉴定.耐冷性的获得途径主要有冷驯化、激素处理、热激处理和培育耐低温品种,最重要的途径是耐冷品种选育.黄瓜冷害机理包括细胞膜的流动性降低及透性增加,光合作用被抑制,根系吸收减弱,可溶性糖含量减少,淀粉粒积累增加,微管的稳定性受到破坏等.黄瓜低温发芽能力由非加性基因决定,而幼苗时期主要由加性基因控制.黄瓜耐冷的分子遗传学研究进展缓慢,目前已克隆出在低温锻炼中特异表达的功能未知的基因CCRl8.今后还应研究黄瓜低温胁迫时的信号转导系统,以进一步揭示黄瓜的冷害机理;利用野生资源的抗逆性状,拓宽栽培黄瓜的遗传基础,选育适于保护地栽培的耐低温品种.     

Purification of an Aminopeptidase Preferentially Releasing N-terminal Alanine from Cucumber Leaves and Its Identification as a Plant Aminopeptidase N

In this study, a highly active foliar aminopeptidase preferentially releasing N-terminal alanine from artificial substrates was purified and characterized from cucumber (Cucumis sativus L. suyo). The enzyme had a molecular mass of 200 kDa consisting of two subunits of 95 kDa. It was a metalloprotease the pH optimum of which was 8 to 9. It cleaved Ala-, Gly-, Met-, Ser-, Leu-, Lys-, and Arg artificial substrates. An internal amino acid sequence was similar to those of aminopeptidase N (clan MA, family M1) of microorganisms, and was very similar to that of a putative aminopeptidase N of Arabidopsis thaliana. From these results, the highly active aminopeptidase in cucumber leaves was identified to be a plant aminopepitdase N.     

黄瓜毛状根的诱导及细胞分裂素6-BA对其生长和形态的影响

含农杆碱型Ri质粒pRiA4b的发根农杆菌(Agrobacteriumrhizogenes)ATCC15834感染黄瓜子叶外植体5d后产生毛状根,毛状根可直接从叶片外植体叶脉处产生。感染10d后,约90%的子叶外植体产生毛状根。毛状根能在无外源生长调节剂的MS固体和液体培养基上自主生长。PCR扩增结果证实,发根农杆菌Ri质粒的rolB和rolC基因已在黄瓜毛状根基因组中整合并得到表达。挑选一无菌黄瓜毛状根系置于含不同浓度6-BA的MS培养基中悬浮培养来探讨细胞分裂素6-BA对黄瓜毛状根生长及其形态变化的影响。结果表明,细胞分裂素6-BA能促进黄瓜毛状根的生长及改变其生长形态。随着培养基中6-BA浓度的升高,黄瓜毛状根变得越来越短而粗,更少分枝。与对照相比,培养基中添加0·1~3·0mg/L6-BA能推迟毛状根最大生长峰的出现,降低其可溶性蛋白含量、SOD和POD酶活性;而黄瓜毛状根的乙烯释放高峰比其最大生长峰和SOD和POD酶活性高峰提前5天,但6-BA处理能降低毛状根的内源乙烯释放量。该结果表明细胞分裂素6-BA可能通过对乙烯生成和释放的调节来影响黄瓜毛状根的生长和形态并延缓毛状根的衰老。     

The Effects of Root Treatment with Various Stress Agents on Plant Cold- and Heat-Tolerance

The root systems of cucumber (Cucumis sativus L.), wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) plants were subjected to a short-term (6–7-h-long) treatment with low and high temperatures, sodium chloride, and lead nitrate, and the effect of these treatments on the changes in the cold- and heat-tolerance of leaf cells was determined. It was established that chilling of cucumber and wheat seedling roots at 10 and 2°C, respectively, or their heating at 38°C and 40°C, respectively, induced an increase in both cold- and heat-tolerance of leaf cells. An increase in the cold- and heat-tolerance was also observed in roots treated with sodium chloride at concentrations of 0.15 M (cucumber) and 0.2 M (wheat), as well as with lead nitrate at a concentration of 0.1 mM (barley, wheat). The tolerance increase induced by these stress agents was accompanied by a considerable increase in the ABA concentration in leaves. The effect of physical and chemical stress agents is suggested to induce the same nonspecific changes in the aboveground organs. These changes bring about, directly or indirectly, an increase in the cold- and heat-tolerance and are related to an increase in the ABA content.     

GA诱导NaCl胁迫下黄瓜种子萌发和幼苗耐盐性效应

研究外源GA对NaCl胁迫下黄瓜种子萌发和幼苗生长的影响.结果显示:(1)0和75mmol·L-1NaCl处理可促进种子萌发,浓度为100mmol·L-1及以上时,随着浓度的增加,种子萌发受抑程度越严重;(2)150mmol·L-1NaCl胁迫下,添加外源GA可显著提高黄瓜种子发芽率、发芽势、发芽指数、活力指数和a-淀粉酶活性;促进种子萌发,以100和150mg·L-1GA处理效果较好;(3)外源GA显著提高幼苗生物量,提高SOD和POD活性,降低MDA含量,以100mg·L-1GA处理效果较好.研究表明一定范围的外源GA可缓解盐害对黄瓜种子萌发和幼苗生长的抑制作用,诱导其耐盐性的提高.     

钙对烟草叶片热激忍耐和活性氧代谢的影响

热胁迫导致烟草叶片细胞膜系统显著受损,表现为SOD活性降低和MDA含量明显升高,叶片叶绿素含量下降,活性氧增加。10mmol/LcaCl2溶液处理烟草幼苗后,能有效降低热胁迫下叶片细胞膜透性,维持较高的SOD和CAT等抗氧化酶活性,减缓O2^-形成和膜脂过氧化反应。研究结果表明,CaCl2处理提高了烟草叶片膜稳定性和膜保护酶活性,有利于保护细胞膜结构,降低高温对烟草幼苗的伤害。钙离子螯合剂EGTA能在一定程度上降低烟草叶片的抗热性。     

增强UV-B辐射与CO2浓度倍增复合作用对冬季大棚黄瓜生长发育的影响

研究了不同剂量的紫外-B辐射与浓度倍增的CO2复合处理对大棚黄瓜(Cucumis sativus)生长发育过程中植株形态、叶绿素、可溶性蛋白质含量以及SOD、POD、CAT酶活性的影响。结果表明：作形态方面,UV-B辐射明显降低了植株的株高、叶柄长度、叶面积,而茎粗增加。复合处理B2C明显提高了黄瓜叶绿素的含量,整个处理对黄瓜蛋白质的含量没有大的影响;酶活性以B2C处理时,其SOD、POD、CAT酶活性最高。说明一定低剂量的UV-B与CO2相复合时,可以促进黄瓜的生长发育,其促进程度大于CO2单因子的效应。     

干旱与氧化胁迫对小麦根氧化还原状态和叶片ABA积累的影响

通过分析一氧化氮(nitric oxide,NO)、活性氧(reactive oxygen species,ROS)和干旱胁迫对小麦根氧化还原状态和叶片脱落酸(abscisic acid,ABA)积累的影响,探讨了干旱胁迫下NO和H2O2调节ABA合成的可能机制。结果表明:干旱胁迫处理初期小麦根还原型谷胱甘肽含量降低、抗氧化酶活性发生振荡变化,细胞氧化还原状态向氧化型转变。NO和H2O2能模拟干旱胁迫的作用使细胞状态向氧化型转变,还可以使小麦叶片ABA积累量上升。干旱胁迫下NO和H2O2对ABA合成的调节作用可能是通过调节细胞氧化还原状态进行。     

硝酸银对雌性黄瓜植株三种氧化酶同工酶的影响

雌性黄瓜植株经硝酸银处理后其茎尖和真叶过氧化物酶活性极显著地增加,茎尖２４小时、真叶３６小时酶活性达到最大值,分别增加１７８．２％和２８４．６％,随后酶活性逐渐下降,但酶活性仍然较对照植株高。多酚氧化酶和超氧化物歧化酶的同工酶活性也增加。同时硝酸银能诱发黄瓜植株过氧化物酶、多酚氧化酶和超氧化物歧化酶产生新的同工酶。用等电聚焦更能有效地观察新产生的同工酶。     

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。     

光合菌对黄瓜光合及抗氧化同工酶的影响

以2种基因型的黄瓜（Cucumis sativus）为材料,研究光合菌（PSB）的喷施对植物生物量、净光合速率（Pn）、叶片PSII的最大光化学效率（Fv／Fm）及抗氧化同工酶代谢的影响。结果表明,喷施PSB均能诱导2种基因型黄瓜的生物量显著增加,并伴随Pn的显著提高。但是,2种基因型黄瓜的Fv/Fm并不受PSB喷施的影响：PSB能使总过氧化物歧化酶（soo）和抗坏血酸过氧化酶（APX）活性提高,并使它们的多数同工酶的活性上调,这些同工酶活性的增加在叶绿体中表现更为明显（如Cu／Zn-SOD、Fe-SOD和sAPX）。研究结果表明,PSB能通过增强黄瓜抗氧化酶体系的活性改善植株的抗氧化能力,从而在植株的生长和光合作用方面起到促进作用。     

Ca2+对根际低氧胁迫下黄瓜幼苗生长和叶片荧光特性的影响

采用营养液栽培,以根际低氧耐性不同的2个黄瓜品种为试验材料,研究了Ca2 对根际低氧胁迫下黄瓜幼苗生长和叶片荧光特性的影响。结果表明:(1)根际低氧胁迫下,黄瓜植株根长、根表面积和根尖数减少,但根径有所增大;叶片干重、鲜重和叶面积显著减小,提高营养液钙浓度可使植株叶片干、鲜重和叶面积得到部分恢复。(2)根际低氧胁迫下,叶片光合色素含量降低,提高营养液钙浓度对色素含量无明显影响。(3)根际低氧胁迫下,常钙和高钙处理黄瓜叶片Fv/Fm与通气常钙(CK)无显著差异,但低氧缺钙处理的Fv/Fm显著降低;与通气常钙相比,根际低氧胁迫处理的光化学猝灭(qP)减小、非光化学猝灭(qN)增大、光合功能相对限制值(L(PFD))升高,提高营养液钙浓度可使qP和qN恢复至近对照水平,而使L(PFD)低于对照,且‘绿霸春四号’黄瓜品种表现得更为突出;根际低氧胁迫下,光化学速率(Prate)减小,天线热耗散速率(Drate)都随钙浓度升高而降低。总之,根际低氧胁迫下黄瓜幼苗生长被显著抑制,PSⅡ反应中心受到一定程度的破坏,提高钙浓度可使PSII反应中心恢复至接近甚至高于通气对照的水平,从而有效缓解根际低氧胁迫对黄瓜幼苗造成的伤害。