小麦的高温伤害与高温适应

小麦叶片经受30分钟高温胁迫后,其电解质伤害性渗漏量（IL）随胁迫温度而增加,两者关系符合指数曲线性质,但超过某一临界温度时,曲线突然变陡,IL的温度系数（Q10）比临界温度之前增加数十倍至数百倍,该临界温度大致相当于或略高于致死温度,麦株经适当高温锻炼后,致死温度及IL达50％时的温度（IT50）均显著增高,但恢复常温后,锻炼效果逐渐解除。     

高温胁迫对根瘤菌Tn5在土壤中的存活及其表型表达的影响

研究了３株弗氏中华根瘤菌（Ｒｈｉｚｏｂｉｕｍｆｒｅｄｉｉ）Ｔｎｓ突变株于适宜温度和高温胁迫两种条件下在土壤中的存活和Ｔｎｓ表型的表达．在适宜温度（２８℃）条件下的灭菌和未灭菌土壤中的存活研究表明生物因素抑制了突变株和野生型的生长．但野生型和突变株的存活种群密度之间无显著差异（Ｐ＝０．０１）．在高温胁迫（４０℃）条件下,土壤中野生型和突变株的种群密度迅速下降,其中部分ＯＮ－２和ＯＮ－３细胞丢失了Ｔｎｓ表型,说明部分细菌的Ｔｎ５表型在高温胁迫条件下不能表达．     

短时高温胁迫对瓜实蝇生长发育及繁殖的影响

为明确瓜实蝇对短时高温胁迫的耐受性。利用人工气候箱模拟短时高温胁迫,测定了不同高温处理(34、36、38、40、42、44、46、48℃)12 h,对不同发育阶段瓜实蝇的存活率和生长发育的影响。结果表明短时高温显著影响瓜实蝇的存活,随温度升高,瓜实蝇各虫态的存活率逐渐降低;高温处理12 h后瓜实蝇卵、幼虫、蛹、雌成虫、雄成虫的致死中温度LT 50分别为35.48、37.55、41.85、43.62、43.32℃;34~42℃短时高温胁迫对瓜实蝇各虫态的发育历期无明显影响,44℃时其发育历期均显著增长;46℃、48℃处理下各虫态死亡率较高,不能正常发育;随着处理温度的升高,雌成虫产卵前期不断增长,单雌产卵量呈下降趋势,成虫寿命不断缩短,后代雌性比增大。44℃及以上的短时高温胁迫不利于瓜实蝇的生长发育,40℃及以上的短时高温胁迫不利于瓜实蝇的繁殖,雌性瓜实蝇对短时高温的胁迫的适应性强于雄性,随着处理温度的升高,后代雌性比例增大。     

高温胁迫对两种常绿杜鹃亚属植物幼苗生理生化特性的影响

为探明常绿杜鹃亚属植物高温致伤的生理机制,以猴头杜鹃（Rhododendron simiarum Hance）、井冈山杜鹃（R.jinggangshanicumTam）四年生实生苗为材料,通过人工气候箱中的盆栽实验,研究了不同程度的高温胁迫对两种常绿亚属杜鹃幼苗叶片生理生化特性的影响。结果表明：（1）两种杜鹃叶片的丙二醛（MDA）、过氧化氢（H2O2）及脯氨酸（Pro）、可溶性蛋白质含量均随胁迫温度的升高而增大;猴头杜鹃的H2O2、可溶性蛋白含量及增幅均明显小于井冈山杜鹃,而MDA、Pro的增幅则因胁迫温度而异。（2）两种杜鹃叶片抗坏血酸（AsA）含量均随胁迫温度的升高而降低,但猴头杜鹃的降幅小于井冈山杜鹃。（3）高温胁迫下,猴头杜鹃除过氧化氢酶（CAT）活性增幅略小外,超氧化物歧化酶（SOD）、过氧化物酶（POD）及抗坏血酸过氧化物酶（APX）增幅均大于井冈山杜鹃。可见,随着胁迫温度的升高两种杜鹃叶片膜脂过氧化作用加重,而猴头杜鹃较井冈山杜鹃具有更强的酶促和非酶促清除活性氧能力。     

外源褪黑素对高温胁迫条件下黄瓜幼苗氮代谢的影响

以‘津优4号’（热敏感型）和‘美国保尔’（耐热型）黄瓜幼苗为试材,研究了叶面喷施褪黑素对高温胁迫条件下黄瓜幼苗氮代谢的影响。结果显示,高温胁迫下,（1）两种黄瓜幼苗硝态氮含量先升高后降低,‘津优4号’总氮和氨态氮含量先下降后持续升高,而‘美国保尔’总氮和氨态氮含量持续上升;（2）两种黄瓜幼苗硝酸还原酶（NR）活性均先上升后下降,而谷氨酰胺合成酶（Gs）、谷氨酸合成酶（GOGAT）和谷氨酸脱氢酶（GDH）均持续下降,‘美国保尔’的4种酶活性下降幅度显著低于‘津优4号’。研究结果表明,叶面喷施褪黑素可有效缓解高温胁迫对NR、GS、GOGAT和GDH的抑制作用,显著增加硝态氮含量,降低氨态氮含量,减轻氨态氮积累对黄瓜幼苗造成的毒害作用,增强高温胁迫条件下黄瓜幼苗氮素的代谢能力,减轻高温胁迫对黄瓜幼苗造成的伤害,提高黄瓜幼苗抵御高温胁迫的能力。     

高温胁迫及其持续时间对棉蚜死亡和繁殖的影响

为探索高温胁迫对棉蚜的影响,室内采用叶子圆片培养基饲养棉蚜的方法,研究不同温度(32,34,36,38,40℃)、不同处理时间(1,2,4,6h)对棉蚜死亡和繁殖的影响.结果表明:棉蚜每日死亡率可用互补重对数模型较好地拟合.随着温度的升高和持续天数的延长,棉蚜累计死亡率呈上升趋势,38 ℃条件下其累计死亡率明显迅速上升.棉蚜半数致死温度随着每天高温处理时间的增加和高温持续天数的延长而降低,且第1-2天下降明显.棉蚜繁殖率随着温度的升高呈下降趋势,每天处理时间不同其繁殖率规律不同,但均是在38℃时下降最多.38℃可能是棉蚜耐高温能力的拐点.研究结果为提高棉蚜种群预测准确性、科学决策最佳化学防治时间提供依据.     

短期高温胁迫对高产小麦品系灌浆后期旗叶光系统Ⅱ功能的影响

以叶绿素快相荧光动力学曲线(OJIP)为探针,探讨了高温胁迫对高产小麦品系01-35灌浆后期光系统Ⅱ（PSⅡ）功能的影响.结果表明,在37 ℃～43 ℃范围内,随温度升高Q_A还原程度和还原速率增大,至43 ℃时分别比室温下增加了23.89%和24.09%,表明Q_A→Q_B的电子传递受到抑制;43 ℃时PSⅡ的电子受体库降至室温下的47.4%,表明高温胁迫伤害了PSⅡ受体库;而PSⅡ供体侧未受到影响.当温度达到46 ℃时,Q_A还原程度和还原速率分别比室温下增加了13.95%和20.48%,但比43 ℃时显著下降,而PSⅡ电子受体库与43 ℃时相比无显著变化,表明46 ℃时PSⅡ供体侧受到伤害.与对照品种鲁麦14相比,高温胁迫下高产小麦的捕光色素复合体仍能捕获较多的光能,而且将捕获的光能更多的用于电子传递,表明高产小麦的捕光色素复合体及电子传递体耐受高温的能力较强,能够维持较高的电子传递能力.     

高温胁迫下苋菜的叶绿素荧光特性

为了探明高温胁迫对苋菜(Amaranthus tricolor L.)光合过程的影响,用不同温度(25、30、35、40、45℃)处理苋菜植株1h后,随即测定了其叶绿素荧光动力学参数和快速光响应曲线特征参数的变化.结果表明:40℃以上高温胁迫下,苋菜叶片的光系统Ⅱ(PSⅡ)潜在光化学效率(Fv/Fo)、最大光化学效率(Fv/Fm)下降;最大荧光(Fm)、光合电子传递速率(ETR)、PSⅡ实际光化学效率(Yield)、光化学淬灭系数(qP)也均有所下降;而初始荧光(F.)和非光化学淬灭系数(NPQ)在40℃以上高温胁迫下显著上升.叶绿素荧光快速光响应曲线测定结果表明,初始斜率α、最大相对电子传递速率ETRmax和半饱和光强Ik在40℃以上高温胁迫下有所下降.研究表明,40℃以上高温胁迫对苋菜的光能的吸收、转换、光合电子传递和强光耐受能力等均有一定的影响.     

短时间亚高温对蓖麻叶中几个与抗逆性有关生理指标的影响

检测了短时间亚高温胁迫下盆栽40片叶龄的蓖麻叶中几个与抗逆性有关生理指标变化的结果表明,温度低于38℃时,蓖麻的叶绿素含量缓慢下降,高于38℃时,呈快速下降趋势;随着温度的升高,游离脯氨酸、丙二醛（MDA）含量和相对膜透性呈上升趋势,46℃下达到最大值;超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的活性在低于43℃时与温度变化呈正相关,超过43℃则迅速下降。     

高温对仁用杏光合特性及PSⅡ光化学活性的影响

为探讨高温胁迫下仁用杏叶片的光合适应机制,以科尔沁沙地生长的4年生'超仁'仁用杏为试材,设置环境温度为25℃、30℃、40℃和50℃处理,利用气体交换技术和快速叶绿素荧光诱导动力学曲线分析技术(JIP-test),研究了仁用杏叶片光合特性和PSⅡ光化学活性.结果表明:在一定温度范围内,随着温度升高,仁用杏通过提高光合色素含量和比例来维持光能的吸收、传递和转换能力,从而保证光合机构正常运转;当高温超过叶片自身生理调节限度后,叶绿素发生分解、净光合速率(Pn)明显下降、胞间CO2浓度(Ci)上升,说明光合作用的下降是由叶肉因素造成的.温度40℃导致单位面积有活性反应中心数量(RC/CSo)显著下降;而50℃高温下荧光诱导曲线中K点(Wk)和J点(Vj)明显增加,高温对仁用杏叶片放氧复合体(OEC)、受体侧和PsⅡ反应中心造成了伤害.此外,50℃高温还导致初始荧光(Fo)显著升高,为对照的2.26倍,PSⅡ最大光化学效率(Fv/Fm)和光化学性能指数(PI/ABS)分别下降为对照的37.9%和10.3%.高温损害了PSⅡ供体侧和受体侧的功能,造成光合效率下降,这是高温胁迫对仁用杏叶片光合机构伤害的主要机制之一.     

高温胁迫对桃和抽细胞膜透性和光合色素的影响

研究了桃和袖离休叶片在高温胁迫下细胞膜透性（电解质渗漏和Pi渗漏）和光合色素的变化及其与抗热性的关系。结果表明。①高温处理下,无论是黑暗条件下浸水24h,还是光照条件下浸水24h,两种果树的电解质和Pi渗漏都显著增加,光照有利于膜的修复;②高温引起Chl含量下降,Chla／b比值上升;③上述这些生理反应与果树的抗热性有关,可用于果树的抗热性鉴定。     

Genome-wide association study for electrolyte leakage in rapeseed/canola (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Freezing temperature/frosts can cause significant damage to plants by rupturing plant cells. Rapeseed/canola (Brassica napus L.) is susceptible to freezing temperature at early seedling stage. The degree of cell rupture or seedling damage can be evaluated through the measurement of electrolyte leakage. Here, we measured the electrolyte leakage of a diversity panel of B. napus germplasm accessions under simulated freezing conditions. Preliminary data for electrolyte leakage measurement indicated that cold acclimation of two-week-old seedlings for 7 days at 4 °C followed by freezing treatment at ??12 °C for 2 h provided a reasonable diversity in response. With this protocol for electrolyte leakage, a genome-wide association study was conducted on 157 winter, semi-winter, and spring types of B. napus accessions that originated from 17 countries. A total of 37,454 single-nucleotide polymorphism (SNP) markers based upon genotyping-by-sequencing were used for the analysis. Ten QTL were identified as associated with electrolyte leakage of canola seedlings, which together explained 43% phenotypic variation. Five of the QTL were located on A-genome. We identified at least 33 orthologs of the functional candidate genes. Although no well-characterized cold regulatory genes were identified, there were some indications that genes involved in membrane structure, developmental processes, and extracellular transport may be involved in altering the electrolyte leakage following the short-term hard freeze and rapid defrosting suffered by the plants in our protocol.     

Thermal acclimation in Arabidopsis lyrata: genotypic costs and transcriptional changes

Frost and heat events can be challenging for sessile organisms that cannot escape thermal extremes. However, adverse effects of thermal stress on fitness may be reduced by pre‐exposure to cold or heat, a process known as acclimation. To understand the ecological and evolutionary implications of acclimation, we investigated (1) the reduction in performance due to stress pre‐exposure, (2) the magnitude of increased leaf resistance to subsequent stress, (3) the costs of acclimation and (4) the genes differing in expression due to stress pre‐exposure. Plants of Arabidopsis lyrata were raised under three treatments of pre‐exposure: bouts of frost, bouts of heat or constant temperature. Resistance of leaves to subsequent frost and heat stress was then measured by electrolyte leakage. RNA‐seq analysis was performed to examine the genes differentially expressed between stress‐pre‐exposed and control plants. Pre‐exposure to stress during growth decreased plant size and increased leaf resistance to subsequent stress independent of whether pre‐exposure was to frost or heat. But the highest increase in leaf resistance to frost was found after pre‐exposure to frost (as a trend) and in leaf resistance to heat after pre‐exposure to heat. No evidence for costs of acclimation was detected. RNA‐sequencing suggested that acclimation by frost and heat pre‐exposure was caused by distinct mechanisms: modification of the chloroplast membrane and modification of the cell wall and membrane, respectively. Our results suggest that thermal resistance is a labile complex of traits, strongly affected by the previously experienced stress environment, with undetermined costs.     

Characterization of a Gene for Spinach CAP160 and Expression of Two Spinach Cold-Acclimation Proteins in Tobacco

The cDNA sequence for CAP160, an acidic protein previously linked with cold acclimation in spinach (Spinacia oleracea L.), was characterized and found to encode a novel acidic protein of 780 amino acids having very limited homology to a pair of Arabidopsis thaliana stress-regulated proteins, rd29A and rd29B. The lack of similarity in the structural organization of the spinach and Arabidopsis genes highlights the absence of a high degree of conservation of this cold-stress gene across taxonomic boundaries. The protein has several unique motifs that may relate to its function during cold stress. Expression of the CAP160 mRNA was increased by low-temperature exposure and water stress in a manner consistent with a probable function during stresses that involve dehydration. The coding sequences for CAP160 and CAP85, another spinach cold-stress protein, were introduced into tobacco (Nicotiana tabacum) under the control of the 35S promoter using Agrobacterium tumefaciens-based transformation. Tobacco plants expressing the proteins individually or coexpressing both proteins were evaluated for relative freezing-stress tolerance. The killing temperature for 50% of the cells of the transgenic plants was not different from that of the wild-type plants. As determined by a more sensitive time/temperature kinetic study, plants expressing the spinach proteins had slightly lower levels of electrolyte leakage than wild-type plants, indicative of a small reduction of freezing-stress injury. Clearly, the heterologous expression of two cold-stress proteins had no profound influence on stress tolerance, a result that is consistent with the quantitative nature of cold-stress-tolerance traits.     

Effects of acclimation on the thermal tolerance of the brown planthopper Nilaparvata lugens (Stål)

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常绿木兰科植物的抗寒性研究

连续4个冬季,对16种常绿木兰科植物进行了田间受冻程度观察,用电导法追踪了抗冻崩溃点温度的变化,并调查了这些树种在自然分布区北缘和垂直分布上缘30a内经历的最低气温,发现3者的种间差异相当一致。同时发现各树种的崩溃点温度最低值与它的生态分布北缘和上缘的常年最低气温接近,由此提出了生态分布最低温度的概念。它能较准确地指示植物的最大抗寒能力,从而有可能避免引种和推广工作中的盲目性。 文章还根据上海近100余年的低温资料,对这16个树种在今后越冬和春季萌发时可能受冻的前景做了预测。     

Thermal acclimation of leaf respiration but not photosynthesis in Populus deltoides x nigra

Dark respiration and photosynthesis were measured in leaves of poplar Populus deltoides x nigra ('Veronese') saplings to investigate the extent of respiratory and photosynthetic acclimation in pre-existing and newly emerged leaves to abrupt changes in air temperature. The saplings were grown at three temperature regimes and at high and low nitrogen availabilities. Rates of photosynthesis and dark respiration (R(d)) were measured at the initial temperature and the saplings were then transferred to a different temperature regime, where the plants remained for a second and third round of measurements on pre-existing and newly emerged leaves. Acclimation of photosynthesis was limited following transfer to warmer or cooler growing conditions. There was strong evidence of cold and warm acclimation of R(d) to growth temperature, but this was limited in pre-existing leaves. Full acclimation of R(d )was restricted to newly emerged leaves grown at the new growth temperature. These findings indicate that the extent of thermal acclimation differs significantly between photosynthesis and respiration. Importantly, pre-existing leaves in poplar were capable of some respiratory acclimation, but full acclimation was observed only in newly emerged leaves. The R(d)/A(max) ratio declined at higher growth temperatures, and nitrogen status of leaves had little impact on the degree of acclimation.     

Electrolyte leakage and lipid degradation account for cold sensitivity in leaves of Coffea sp. plants

Five Coffea genotypes differing in their sensitivity to low positive temperatures were compared with regard to the effects of chilling on membrane integrity, as well as their ability to recover from cold-induced injury upon re-warming. Membrane damage was evaluated through electrolyte leakage, changes in membrane lipid composition and malondialdehyde (MDA) production in control conditions (25/20 degrees C, day/night), after a gradual temperature decrease period to 15/10 degrees C, after chilling treatment (3 nights at 4 degrees C) and upon re-warming to 25/20 degrees C during 6 days (recovery). C. dewevrei showed the highest electrolyte leakage at 15/10 degrees C and after chilling. This was due mainly to lipid degradation observed at 15/10 degrees C, reflecting strong membrane damage. Furthermore, MDA production after chilling conditions indicated the occurrence of lipid peroxidation. A higher susceptibility of C. dewevrei to cold also was inferred from the complete absence of recovery as regards permeability, contrary to what was observed in the remaining plants. Apoat? and Piat? presented significant leakage values after chilling. However, such effects were reversible under recovery conditions. Exposure to cold (15/10 degrees C and 3 x 15/4 degrees C) did not significantly affect membrane permeability in Catuaí and Icatú. Furthermore, no significant MDA production was observed even after chilling treatments in Apoat?, Piat?, Catuaí and Icatú, suggesting that the four genotypes had the ability to maintain membrane integrity and/or repair membrane damage caused by low temperatures. Apoat?, Piat? and, to a lower extent, Catuaí, were able to cope with gradual temperature decrease through an enhanced lipid biosynthesis. After acclimation, Piat? and Catuaí showed a lowering of digalactosyldiacylglycerol to monogalactosyldiacylglycerol ratio (MGDG/DGDG) as a result of enhanced DGDG synthesis, which represents an increase in membrane stability. The same was observed in Apoat? after chilling, in spite of phospholipids decrease. The studied parameters clearly indicated that chilling induced irreversible membrane damage in C. dewevrei. We also concluded that increased lipid synthesis, lower MGDG/DGDG ratio, and changes in membrane unsaturation occurring during acclimation to low temperatures may be critical factors in maintenance of cellular integrity under chilling.     

Acclimation to temperature and death at changing lethal temperatures in the freshwater fish Chalcalburnues chalcoides

1. 1.|In the freshwater fish Chalcalburnus chalcoides, an increase in the body (standard) size caused decreases in the upper LT-50 from 36.6° to 36.0°C and lower LT-50 from 6.3° to 5.3°C

2. 2.|The fish acclimated to constant temperatures between 10°C and 30°C showed reasonable heat acclimation and also reasonable cold acclimation. Thus, an increase in the acclimation temperature from 10°C to 30°C caused increases in the upper LT-50 from 34° to 36.2°C and the lower LT-50 from 1.25 to 6.5°C.

3. 3|The mean survival time — temperature curves of 10°, 20° and 30°C acclimated fish at various constant temperatures showed decreased in the survival tim ewith increasing lethal temperatures. Furthermore, an increase in the acclimation temperature causes a shift in the survival duration-temperature curve to the right, i.e., the fish become more heat resistant. Thus, the mean survival duration of 10°, 20° and 30°C acclimated fish at 35°C were 7.5, 79.6 and 530 minutes, respectively.

4. 4.|The effect of the thermal experience to changing lethal temperatures depends on the first lethal temperature to which the fish were exposed as well as the sequence of temperature changes. In the experiments in which the first lethal temperatures were between 32° and 34°C and the temperature was varied in an ascending order, their thermal resistance was increased and the fish required 114 to 174% of the expected lethal doses to die while in the experiments in which the starting temperature were between 38° and 40°C and the temperature varied in descending order, the fish become more sensitive to the upper lethal temperature and they died after receiving only 62 to 81% of the expected lethal doses. Thus, with a gradual increase in the lethal temperature, the fish show additional acclimation in the zone of resistance which in turn causes an increase in the thermal resistance. This may have ecological significance in nature.