土壤干旱胁迫和复水后3个杨树品种叶片部分生理指标变化及抗旱性评价

以美洲黑杨品种‘2025’（Populus×deltoides‘2025’）及其2个芽变彩叶品种‘全红杨’（P.×deltoides‘Quanhong’）和‘中红杨’（P.×deltoides‘Zhonghong’）当年生嫁接苗为实验材料,对土壤干旱胁迫0、4、7、14、21和28d以及复水7d后叶片中MDA含量及PPO、SOD、CAT和POD活性的变化以及MDA含量与4种酶活性的相关性进行了分析,并采用隶属函数法和灰色关联分析法对3个品种的抗旱性进行综合评价。结果表明：随干旱胁迫时间的延长,3个品种的MDA含量总体呈增加趋势,并在处理的中期和后期显著或极显著高于各自的对照;PPO和SOD活性总体上先升高后降低,均在处理的前期和中期高于各自的对照;‘中红杨’和‘2025’的CAT活性先升高后下降,而‘全红杨’的CAT活性持续下降,均在处理14d后极显著或显著低于各自的对照;‘全红杨’和‘2025’的POD活性先降低后升高且均低于各自的对照,而‘中红杨’的POD活性则呈波动趋势但总体上与对照无显著差异。复水7d后,3个品种的MDA含量均有所降低,而PPO和CAT活性均有所提高;‘全红杨’和‘2025’的SOD和POD活性升高,而‘中红杨’的SOD和POD活性则降低。在土壤干旱胁迫条件下,仅‘全红杨’的PPO和CAT活性与MDA含量以及‘中红杨’的CAT活性与MDA含量呈极显著负相关,各品种的其他酶活性与MDA含量均无显著相关性。‘全红杨’、‘中红杨’和‘2025’的平均隶属函数值分别为0.482、0.527和0.533,据此判断3个品种中‘2025’的抗旱性最强、‘全红杨’的抗旱性最弱。3个品种抗旱性与各生理指标的关联度均大于0.64,其中与CAT和PPO活性的关联度分别为0.793和0.761,因而,可将CAT和PPO活性作为评价杨树品种抗旱性的首选指标。     

Genotype differences in the metabolism of proline and polyamines under moderate drought in tomato plants

Water stress is one of the most important factors limiting the growth and productivity of crops. The implication of compatible osmolytes such as proline and polyamines in osmotic adjustment has been widely described in numerous plants species under stress conditions. In the present study, we investigated the response of five cherry tomato cultivars (Solanum lycopersicum L.) subjected to moderate water stress in order to shed light on the involvement of proline and polyamine metabolism in the mechanisms of tolerance to moderate water stress. Our results indicate that the most water stress‐resistant cultivar (Zarina) had increased degradation of proline associated with increased polyamine synthesis, with a higher concentration of spermidine and spermine under stress conditions. In contrast, Josefina, the cultivar most sensitive to water stress, showed a proline accumulation associated with increased synthesis after being subjected to stress. In turn, in this cultivar, no rise in polyamine synthesis was detected. Therefore, all the data appear to indicate that polyamine metabolism is more involved in the tolerance response to moderate water stress.     

Partitioning of sugars in Lolium perenne (perennial ryegrass) during drought and on rewatering

Simulated swards of perennial ryegrass ( Lolium perenne ) growing in 1-m³ soil blocks in the glasshouse were either well watered or deprived of water for 57 d and then rewatered. The first aim was to measure effects of drought on sugar (water-soluble carbohydrate) composition of laminae and sheaths of mature laminae, and bases and laminae of young (growing) leaves. The second aim was to use pulse labelling with ¹⁴CO₂ to follow the partitioning of recently-fixed assimilates, and the assembly and consumption of reserve sugars (fructans). Over the last 7 d of drought growth almost stopped, old leaves died faster than they were replaced, and total sugar (which had doubled in concentration during drought) was rapidly consumed. Leaf laminae had lower content of total sugars and of large fructan (DP>5) than did growing bases and sheaths. Drought greatly reduced the rate at which sugar was exported from the laminae to the sheaths and growing leaf bases, and the rate at which it was converted to fructan. Nevertheless, fructan accumulated over the first 50 d of drought. Rewatering did not result in depolymerization and remobilization of sugars that had been formed during the last 7 d of drought, but stimulated their further assembly into high-DP fructans. Our hypothesis, that accumulation of neo-kestose (a DP-3 fructan) in droughted laminae was a symptom of sugar remobilization just before death, was disproved. It is concluded that sugar reserves contribute to drought resistance only under extreme conditions. The specific role of fructan in dry environments might be to improve regrowth when drought is relieved, rather than to enhance growth during drought.     

The decoupling between gas exchange and water potential of Cinnamomum camphora seedlings during drought recovery and its relation to ABA accumulation in leaves

气候变化将改变降雨格局,从而导致极端干旱事件增多。然而,树木如何协调生理和生化响应来应对干旱-恢复的机制仍不清楚。本 研究探讨了干旱-恢复过程中树木生理与生化特征的耦联关系。我们首先将香樟(Cinnamomum camphora)盆栽幼苗种植在水分充足的条件下,然后通过停止浇水以达到干旱处理的目的。当幼苗胁迫至轻度干旱(气孔关闭)和中度干旱(ψxylem = −1.5 MPa)时,分别对其进行复水处理。在干旱及复水4天过程中,我们测定了香樟叶片水势、气体交换、脱落酸以及非结构性碳水化合物的变化规律。我们发现干旱强度在很大程度上决定了香樟的生理与生化响应,并影响其干旱后恢复。轻度干旱导致气孔关闭,并引起叶片脱落酸累积和水势下降,而中度干旱可进一步引起叶片脯氨酸累积和非结构性碳水化合物的变化。干旱强度的增加会导致气体交换恢复滞后,但对水势的恢复无显著影响。另外,干旱与复水过程中水势与气体交换之间的关系存在较大差异: 即干旱过程中水势与气体交换存在很强的耦联关系,而这种耦联关系在复水过程中并不存在,其主要原因是由于叶片脱落酸累积,从而延缓了气孔导度的恢复。综上,本研究结果表明,脱落酸可能是导致香樟旱后气孔导度恢复滞后的主要影响因素。此外,干旱强度对树木生理和生化的恢复具有显著影响。     

外源褪黑素对干旱胁迫下黑麦草和苜蓿抗氧化能力及养分吸收的影响

以黑麦草和苜蓿为对象,分别叶面喷施和根施100 μmol·L^-1的褪黑素溶液,在干旱胁迫下测定了生物量、丙二醛(MDA)含量、相对电导率、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、养分含量(有机碳C、全氮N、全磷P)等指标,研究外源褪黑素对干旱胁迫下植物抗氧化能力及养分吸收的影响。结果表明: 干旱胁迫下,黑麦草和苜蓿的地上、地下生物量显著降低,外施褪黑素能够有效缓解干旱胁迫对黑麦草和苜蓿生长的抑制作用,叶面喷施和根施褪黑素使干旱胁迫下黑麦草的生物量分别增加14.5%和29.6%,苜蓿的生物量分别增加36.6%和49.1%。干旱胁迫下,黑麦草的SOD、POD活性和苜蓿的SOD活性显著降低,外施褪黑素显著提高黑麦草和苜蓿的SOD、POD、CAT活性,减少叶片中MDA的积累,使叶片相对电导率显著下降,抗氧化能力显著提高。干旱和外施褪黑素对黑麦草和苜蓿有机碳含量无显著影响。干旱胁迫下,黑麦草叶片和根中的N、P含量以及苜蓿根中的N含量降低,外施褪黑素提高黑麦草和苜蓿根和叶片中的N、P含量,这表明褪黑素对干旱胁迫下黑麦草和苜蓿的养分吸收有一定的调节作用。施用褪黑素不仅能改善植物的抗氧化能力,还能调节养分吸收以增强植物对干旱胁迫的适应性,而且叶面喷施褪黑素效果好于根施。     

咸水浇灌后持续干旱条件下棉花生长及光合作用的变化

用咸水(不同浓度的NaCl溶液)浇灌盆栽棉花植株,随后进行持续干旱处理.测定干旱处理期间棉花的生长情况、光合速率、叶绿素荧光等参数的变化,并对植株的相对含水量、水势、渗透势等水分状况和Na⁺、K⁺含量进行分析,探索环境Na⁺在棉花适应干旱胁迫中的作用.结果表明: 干旱可以明显抑制植株的生长,降低叶片的净光合速率;用25～100 mmol·L^-1NaCl溶液浇灌后进行持续干旱处理的棉花植株,其株高、生物量、净光合速率和F_v/F_m值均明显高于用水浇灌后进行持续干旱处理的植株.同时,前者的土壤和叶片相对含水量、细胞膨压、Na⁺含量也明显高于后者,但植株水势和组织渗透势则显著低于后者,且组织渗透势的降低与Na⁺含量具有显著相关性.上述结果说明,土壤适量Na⁺的存在能够提高土壤和植株的保水力、增加棉花对Na⁺的吸收和积累、降低组织渗透势,从而增强植株吸水力、保持较高的细胞膨压,维持相对较高的光合速率和生长速度.土壤中存在一定浓度的NaCl可以有效缓解干旱对棉花的不利影响.     

Abscisic acid in apoplastic sap can account for the restriction in leaf conductance of white lupins during moderate soil drying and after rewatering

We studied the effects of drought on leaf conductance (g) and on the concentration of abscisic acid (ABA) in the apoplastic sap of Lupinus albus L. leaves. Withholding watering for 5d resulted in complete stomatal closure and in severe leaf water deficit. Leaf water potential fully recovered immediately after rewatering, but the aftereffect of drought on stomata persisted for 2d. ABA and sucrose were quantified in pressurized leaf xylem extrudates. We assumed that the xylem sucrose concentration is negligible and hence that the presence of sucrose in leaf extrudates indicated that they were contaminated by phloem. To eliminate this interference, the concentration of ABA in leaf apoplast was estimated by extrapolation to zero sucrose concentration, using the regression between ABA and sucrose concentrations. The estimated apoplastic ABA concentration increased by 100-fold with soil drying and did not return to pre-stress values immediately following rewatering. g was closely related to the concentration of ABA in leaf apoplast. Furthermore, the feeding of exogenous ABA to leaves detached from well-watered plants brought about the same degree of depression in g as resulted from the drought-induced increase in ABA concentration. We therefore conclude that the observed changes in the concentration of ABA in leaf apoplast were quantitatively adequate to explain drought-induced stomatal closure and the delay in stomatal reopening following rewatering.     

干旱胁迫下坡柳等幼苗质膜相对透性和脯氨酸含量的变化

以金沙江干热河谷主要树种坡柳、银合欢和山毛豆幼苗为材料,通过盆栽苗自然干旱胁迫,同时以浇水处理为对照,探讨了干旱胁迫下三树种幼苗叶片的相对含水量、质膜透性以及脯氨酸含量的变化情况。结果表明,干旱胁迫后三树种叶片的相对含水量、质膜相对透性以及脯氨酸含量都发生了变化,只是变化的幅度和进程不同。三项生理指标的综合分析及结合其自然表现,坡柳具有较强的抗旱能力,其次为银合欢,最后是山毛豆。     

Heterologous expression of the AtDREB1A gene in chrysanthemum increases drought and salt stress tolerance

DNA cassette containing an AtDREB1A cDNA and a nos terminator,driven by a cauli- flower mosaic 35S promoter,or a stress-inducible rd29A promoter,was transformed into the ground cover chrysanthemum(Dendranthema grandiflorum)'Fall Color'genome.Compared with wild type plants,severe growth retardation was observed in 35S:DREB1A plants,but not in rd29A:DREB1A plants.RT-PCR analysis revealed that,under stress conditions,the DREB1A gene was over-expressed constitutively in 35S:DREB1A plants,but was over-expressed inductively in rd29A:DREB1A plants.The transgenic plants exhibited tolerance to drought and salt stress,and the tolerance was significantly stronger in rd29A:DREB1A plants than in 35S:DREB1A plants.Proline content and SOD activity were increased inductively in rd29A:DREB1A plants than in 35S:DREB1A plants under stress conditions.These results indicate that heterologous AtDREB1A can confer drought and salt tolerance in transgenic chrysanthemum,and improvement of the stress tolerance may be related to enhancement of proline content and SOD activity.     

Heterologous expression of the AtDREB1A gene in chrysanthemum increases drought and salt stress tolerance

DNA cassette containing an AtDREB1A cDNA and a nos terminator, driven by a cauliflower mosaic 35S promoter, or a stress-inducible rd29A promoter, was transformed into the ground cover chrysanthemum (Dendranthema grandiflorum) ‘Fall Color’ genome. Compared with wild type plants, severe growth retardation was observed in 35S:DREB1A plants, but not in rd29A:DREB1A plants. RT-PCR analysis revealed that, under stress conditions, the DREB1A gene was over-expressed constitutively in 35S:DREB1A plants, but was over-expressed inductively in rd29A:DREB1A plants. The transgenic plants exhibited tolerance to drought and salt stress, and the tolerance was significantly stronger in rd29A:DREB1A plants than in 35S:DREB1A plants. Proline content and SOD activity were increased inductively in rd29A:DREB1A plants than in 35S:DREB1A plants under stress conditions. These results indicate that heterologous AtDREB1A can confer drought and salt tolerance in transgenic chrysanthemum, and improvement of the stress tolerance may be related to enhancement of proline content and SOD activity.     

关键发育期干旱及复水过程对春玉米主要生理参数的影响

为深入了解玉米在关键发育期干旱条件下的耗水特征及致灾机理,对春玉米‘丹玉39’分别从拔节(T₁)和抽雄(T₂)期开始采用持续无补水方式进行干旱及复水试验,基于对叶和根水势、主要光合变量(净光合速率P_n、蒸腾速率T_r、气孔导度g_s、胞间CO₂浓度C_i)以及茎流速率(SF)的动态观测,研究各生理参数对干旱及复水过程的响应特征.结果表明: 叶、根水势均与土壤湿度呈对数关系,不同时期干旱使二者都减小,对根水势的影响比叶水势提前,与拔节期相比,抽雄期叶水势的干旱响应偏早,根水势偏晚;叶水势在T₁处理复水后能得到恢复,但不能恢复到正常水平,T₂处理不能恢复;T₁处理的根水势对复水的响应比叶水势更快,且更接近于正常水平.P_n和T_r对T₂处理的响应快于T₁处理;复水后二者对T₁处理的恢复速度快于T₂处理,T₁和T₂处理P_n分别超过和达到正常水平,而T_r分别能和不能达到正常水平;T_r对T₁处理的响应早于P_n,二者对T₂处理的响应一致;各处理g_s对干旱的响应与P_n一致;T₁处理的C_i与P_n趋势一致,T₂处理相反.各干旱处理SF比对照减小,在晴天比阴天响应明显,SF对T₂处理的响应比T₁处理敏感,在一定干旱水平后响应敏感性减弱;复水后SF比对照明显增大,T₂处理的增幅小于T₁处理.