低温锻炼与CaCl2处理对毛白杨幼苗可溶性总蛋白、CaM及抗冻性的影响

低温锻炼提高了毛白杨幼苗叶片和枝条中钙调素 (CaM)和可溶性总蛋白含量 ,同时也提高了幼苗的抗冻性 .CaCl2 处理对上述低温锻炼的作用有加强的效果 ,体现在明显提高了CaM和可溶性总蛋白含量以及幼苗抗冻性 ;钙离子螯合剂EGTA、钙离子通道阻断剂LaCl3 或钙调素拮抗剂CPZ处理则减弱了低温锻炼的效应 ,表现出CaM和可溶性总蛋白含量以及幼苗抗冻性明显降低 .进一步研究发现 ,CaCl2 处理的低温锻炼不仅能减轻低温胁迫引起的CaM和可溶性总蛋白含量的下降程度 ,而且有利于幼苗在恢复过程中CaM和可溶性总蛋白水平的迅速回升 .这表明Ca2 + CaM可能参与了CaM和可溶性总蛋白的合成及抗冻性的诱导     

毛白杨抗冻性低温诱导过程中糖的效应(英文)

在低温锻炼和结合蔗糖处理的低温锻炼下 ,对毛白杨 (Populustomentosa)幼苗枝条和叶片的可溶性糖含量 ,以及幼苗存活率和抗冻性分别进行了测定 .结果表明 ,低温锻炼明显提高了幼苗枝条和叶片的可溶性糖含量 ,同时也提高了幼苗的存活率和抗冻性 .2 0 %蔗糖处理对上述低温锻炼的作用有加强的效果 .进一步分析发现 ,无论是单纯的低温锻炼还是结合蔗糖预处理的低温锻炼 ,幼苗枝条中可溶性糖含量的提高程度均较叶片明显 ,而且它们的含量增加与幼苗抗冻性的提高密切相关 .这表明低温锻炼所引起的可溶性糖积累可能参与了幼苗抗冻性的诱导     

甜杨抗冻性低温诱导过程中G6PDHase ,ATPase及蛋白质的变化(英文)

首次研究了低温锻炼对甜杨 (Populussuaveotlens)幼苗抗冻性的效应 ,并对低温锻炼中的G6PDHase ,ATPase及蛋白质的动态变化过程进行了测定 .另外 ,在低温锻炼前用蛋白质合成抑制剂环己亚胺对甜杨幼苗进行预处理 .试验结果表明 ,适当的低温锻炼可明显提高甜杨幼苗的抗冻性 ,但整个低温锻炼过程必须分两个阶段进行 ,第一阶段在 - 10℃的温度下锻炼 6天 ,虽对甜杨幼苗抗冻性的提高效应不明显 ,但它是不可缺少的 ,它可为第二阶段的 - 2 0℃锻炼的进行及抗冻性的完全发育提供基础 .伴随着幼苗枝条中蛋白质含量及G6PDHase和ATPase活性提高的同时 ,也明显提高了幼苗的抗冻性 ;脱锻炼 2天后 ,幼苗抗冻性下降到未锻炼水平 ,而枝条中蛋白质含量及G6PDHase和AT Pase活性虽有下降但略高于未锻炼 .蛋白质合成抑制剂环己亚胺预处理则明显降低了幼苗抗冻性和蛋白质含量 .进一步分析发现 ,低温锻炼中的G6PDHase和ATPase活性及蛋白质含量的变化与幼苗抗冻性的提高密切相关     

钙-钙调素对中东杨扦插苗的诱导抗冻作用

以零下低温锻炼和结合效应剂（CaCl2、钙离子螯合剂EGTA、钙离子通道阻断剂LaCl3或钙调素拮抗剂CPE）处理的低温锻炼下的中东扬扦插苗为试材，对其体内丙二醛（MDA）及钙调素CaM含量，SOD、POD及线粒体Ca^2-＋ATPase活性分别进行测定。结果表明，低温锻炼不仅在一定程度下提高了幼苗CaM含量，提高了SOD、POD和Ca^2＋-ATPase活性，降低了MDA含量；而且减少了低温胁迫所引起的SOD、POD，Ca^2＋＋ATPase和CaM含量的下降程度以及MDA的增加幅度。在低温锻炼的同时。用CaCl2处理能加强低温锻炼的效果，但这种效应可被EGTA、LaCl3或CPZ处理抑制。经低温锻炼后，幼苗中的CaM含量的增加有助于SOD、POD和线粒体Ca^2＋-ATPase活性的提高，进而对幼苗抗冻性的提高有明显的促进作用。     

CaCl2在毛白杨幼苗抗冻性低温诱导中的作用

不同浓度的CaCl2 处理对毛白杨幼苗抗冻性的提高效应是不同的 ,其中 10mmol·L-1CaCl2 处理更有利于幼苗抗冻性的提高 ,而且处理最适宜时间为 5天 .低温锻炼不仅提高了毛白杨幼苗叶片和枝条中钙调素含量 ,同时也提高了幼苗抗冻性 .CaCl2 处理对低温锻炼的作用有加强效果 ,而钙离子螯合剂EGTA、钙离子通道阻断剂LaCl3 或钙调素拮抗剂CPZ处理则减弱低温锻炼效应 ,表现出CaM含量和幼苗抗冻性明显降低 .这表明Ca2 + CaM可能参与了幼苗抗冻性的诱导     

低温锻炼对冷胁迫下油茶幼苗光合速率与抗氧化酶活性的影响

以油茶品种"杂优闽1"为试验材料,以未经低温锻炼的油茶幼苗为对照,研究了油茶幼苗在(10±0.5)℃低温锻炼、(2±0.5)℃冷胁迫和常温恢复期间的光合速率和抗氧化酶活性的变化。结果表明:低温锻炼3 d可明显提高油茶幼苗的抗寒性;冷胁迫3 d,经低温锻炼后的油茶幼苗叶片净光合速率和相对含水量明显高于对照;且其在常温下的恢复也较对照迅速。在低温锻炼和冷胁迫期间,油茶幼苗叶片脯氨酸和可溶性糖含量明显增加,且丙二醛(MDA)含量明显低于对照;经低温锻炼的油茶幼苗叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性则均明显高于未经低温锻炼的油茶幼苗,说明渗透调节物质含量增加和保护酶活性增强在低温锻炼诱导油茶幼苗的抗寒性上发挥着重要的作用。     

低温锻炼对翅荚木幼苗抗氧化酶活性和保护物质的影响

采用梯度降温对翅荚木幼苗进行低温锻炼,测定其在低温锻炼过程中抵御低温保护物质的含量和抗氧化酶的活性,结果表明:低温锻炼使POD和SOD活性明显提高;可溶性蛋白、可溶性糖和脯氨酸含量升高;在脱锻炼期间可溶性蛋白、可溶性糖含量和POD、SOD活性仍略高于或接近于对照水平。     

黑暗和光照条件下低温胁迫对红花玉兰幼苗生理特性的影响

以25℃正常生长的苗木为对照,研究了在黑暗和光照条件下低温(5℃)胁迫对红花玉兰幼苗生理特性的影响,结果表明:低温胁迫下,质膜相对透性升高,可溶性糖及脯氨酸含量增加,且光照处理高于黑暗处理;可溶性蛋白含量下降,且光照处理的含量小于黑暗处理;SOD活性升高,且光照处理高于黑暗处理;光照处理POD活性升高较小,黑暗处理POD活性低于对照。可溶性糖含量、脯氨酸含量、SOD活性的提高可能是植株抗寒性机制的重要因子。     

七叶树幼苗对水分胁迫和复水的生理响应

为了评价1年生七叶树幼苗抗旱性,采用盆栽称重控制土壤含水量下限的方法,设置5个水分处理水平,测定其生理指标动态变化特征。结果表明:随着水分胁迫时间的延长,七叶树幼苗叶绿素总含量、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、过氧化物酶(POD)活性、脯氨酸含量均表现为先升高后降低,电导率、丙二醛(MDA)、可溶性蛋白和可溶性糖含量表现为逐渐增加。在短期胁迫下CAT、SOD、POD活性随胁迫程度的加深而升高,长期胁迫下随胁迫程度的加深而降低;可溶性蛋白含量在短期胁迫下随胁迫程度加深先升高后降低,长期胁迫下其含量先下降后升高;电导率、脯氨酸和可溶性糖含量随胁迫程度的增加而增加;叶绿素总含量随胁迫程度的增加先升高后降低;MDA含量随胁迫程度的增加先减少后增加。复水试验表明各生理指标均有恢复,表现出较强抗旱性,七叶树可以作为干旱地区园林绿化树种。     

外施H2O2对黄瓜幼苗抗低温胁迫的影响

以"津研7号"和"津春4号"黄瓜幼苗为材料,在其生长期外施不同浓度的H2O2,研究了H2O2对黄瓜幼苗抗低温胁迫的影响.结果表明:黄瓜幼苗经低温胁迫后,其电导率和丙二醛含量急剧上升,而过氧化物酶活性和可溶性蛋白含量明显降低;与对照相比,外施H2O2能提高其过氧化物酶活性,降低膜渗漏率,增加可溶性蛋白含量,减缓膜脂过氧化作用,从而提高黄瓜幼苗的抗低温胁迫能力,其中以10 mmol.L-1的H2O2处理效果最为明显.     

Comparison of G6PDH Activity and LT50 Between P.tomentosa and P.suaveolens During Freezing Acclimation

The differences of glucose-6P dehydrogenase(G6PDH) activity and freezing resistance induced by freezing acclima-tion between cuttings of freezing-sensitive P.tomentosa and freezing-resistant P.suaveolens were compared for exploring the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation.After 5d of freezing acclimation at -3℃ ,the LT50 of P.tomentosa has deereased from -6.2℃ incontrol cuttings to -14.3℃ in freezing acclimated ones,and the increase of LT50 of P.tomentosa has decreased from -6.2℃ in control cutting to -14.3℃ in freezing acclimated ones,and the increase of G6PDH activity was observed in freezing acclimated cuttings as compared with control ones.Whereas,when P.suaveolens was freezing acclimated at -20℃ for 5d,the LT50 has decreased from -27.1℃ in control cuttings to -43.5℃ in freezing acclimated ones,and the activity of G6PDH increased considerably.In addition,the increase of LT50 and the decrease of G6PDH activity resulting from 2d of deacclimation at 25℃ were found in two kinds of freezing acclimated cuttings.It is concluded that the increase in the activity of G6PDH may associate with the inherited freezing resistance of species and the enhancemen of freezing resistance of cuttings,and may play an important role in the antifreeze process under freezing temperature,which would provide the basis for the study on the molecular mechanism of freezing resistance in P.suaveolens and the cloning of gene associated with freezing resistance.     

Characterization and Role of Glucose-6-phosphate Dehydrogenase of Populus suaveolens in Induction of Freezing Resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTTred) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTTred, indicating that the purified enzyme probably presented in cytosol of P suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P.suaveolens cuttings were also studied. The results show that G6PDH is characterized by Km value of 360/amol.L^-1 for G6P and 16μmol.L^-1 for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol‘L i except for NADPH and NADH)to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgC12, CaC12 and KC1 (all 1.0 mmol.L^-1) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl2 (1.0 mmol.L-1) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LTs0) of P. suaveolens cuttings during freezing acclimation at -20℃ were investigated. The results reveal that freezing acclimation decreases LTs0 of cuttings, and increases the activity of cytosolic G6PDH compared with control ones,while 2 d of de-acclimation at 25 ~C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT50. Furthermore,the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings.     

The role of antioxidant system in freezing acclimation-induced freezing resistance of Populus suaveolens cuttings

We investigated the changes in the contents of H2O2, malonaldehyde (MDA) and endogenous antioxidants, the activities of protective enzymes and some critical enzymes involved in the ascorbate-glutathione (ASA-GSH) cycle as well as freezing resistance (expressed as LT50) and correlations mentioned above, in detail using Populus suaveolens cuttings. The purpose was to explore the physiological mechanism of the enhancement of freezing resistance induced by freezing acclimation at –20°C, and to elucidate the physiological mechanisms by which trees adapt to freezing. The results showed that freezing acclimation enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), monodehydroascorbate reductase (MDAR), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR). And it increased the contents of reduced ascorbate (ASA), reduced glutathione (GSH), dehydroascorbate (DHA) and oxidized glutathione (GSSG). However, H2O2 and MDA contents and LT50 of cuttings were decreased. LT50 in cuttings was found to be closely correlated to the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, H2O2, MDA, ASA, GSH, DHA and GSSG during freezing acclimation. This suggested that the enhancement of freezing resistance of cuttings induced by freezing acclimation may relate to the distinct increase for the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, ASA, GSH, DHA, and GSSG. In addition, the observed levels of APX, DHAR, MDAR, GR, ASA, DHA, GSH and GSSG were higher than those of SOD, POD and CAT during freezing acclimation. It indicated that a higher capacity of the ASA-GSH cycle is required for H2O2 detoxification, and growth and development of cuttings. Based on the obtained results, it can be concluded that the ASA-GSH cycle plays an important role in enhancement of freezing resistance of P. suaveolens cuttings during freezing acclimation.     

Characterization and role of glucose-6-phosphate dehydrogenase of Populus suaveolens in induction of freezing resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTT_red) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTT_red, indicating that the purified enzyme probably presented in cytosol of P. suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P. suaveolens cuttings were also studied. The results show that G6PDH is characterized by K _m value of 360 μmol·L⁻¹ for G6P and 16 μmol·L⁻¹ for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol·L⁻¹ except for NADPH and NADH) to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgCl₂, CaCl₂ and KCl (all 1.0 mmol·L⁻¹) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl₂ (1.0 mmol·L⁻¹) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LT₅₀) of P. suaveolens cuttings during freezing acclimation at −20 °C were investigated. The results reveal that freezing acclimation decreases LT₅₀ of cuttings, and increases the activity of cytosolic G6PDH compared with control ones, while 2 d of de-acclimation at 25 °C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT₅₀. Furthermore, the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings. [Supported by the Foundation of State-designated Base for Biology Researching and Teaching in Beijing Forestry University]     

日照地区部分竹子的抗寒性研究

冬季低温是竹类植物在我国较高纬度地区园林绿化中得不到进一步推广应用的主要限制因子,为探究其抗寒性机理,扩大引种范围,本文以6个竹种（品种）为试材,测定电解质外渗率并拟合logistic方程求LT50,研究低温对可溶性糖、可溶性蛋白、游离脯氨酸等生理生化指标的影响。结果表明,随着低温胁迫加剧,电解质外渗率呈增加趋势,可溶性糖含量、可溶性蛋白含量、游离脯氨酸含量均表现出先上升后下降的趋势。综合所有抗寒性指标分析得出,6个竹种（品种）抗寒性顺序为：金镶玉竹〉矢竹〉罗汉竹〉苦竹〉箬竹〉鸡毛竹。