抗旱性不同的小麦幼苗对水分和NaCl胁迫的反应

分别测定抗旱小麦的８１３９（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．ｃｖ．８１３９）和干旱敏感品种甘麦８号（Ｔ．ａｅｓｔｉｖｕｍ Ｌ．ｃｖ．Ｇａｎｍａｉ Ｎｏ．８）在２０％ＰＥＧ６０００和１．２％ＮａＣｌ胁迫下的生长、光合作用、蒸腾作用及抗氧化保护系统的变化。结果表明,抗旱小麦８１３９对ＰＥＧ６０００有较强的抗性,但对ＮａＣｌ胁迫的抗性较差。ＮａＣｌ胁迫下,两种小麦根的生长均受到严重抑制,而在ＰＥ     

Response of wheat seedlings to short-term drought stress with particular respect to nitrate utilization

Abstract. The effect of short-term changes in the water potential (from 0 to – 2.5 MPa) by addition of PEG 4000 to the nutrient solution was investigated with respect to nitrate uptake and reduction in 3-week-old wheat plants ( Triticum aestivum , cv Fidel). Plants were harvested at the end of 12-h treatments in the dark. The water potential of the mature leaves was similar to that of the medium down to – 0.8 MPa and was maintained at this level even though the external water potential was much lower. The medium water potential of 0.8 was a threshold level below which elongation of the youngest leaf was inhibited. Increase of the PEG concentration in the medium brought about a decrease of evapotranspiration and enhancement of nitrate uptake. No difference in the rate of nitrate reduction was observed, although the in vitro nitrate reductase activity was lowered. Nitrate accumulation in the shoot was ascribed both to the stimulation of net uptake from the medium, and to the mobilization and translocation of nitrate from the root. It is suggested that increase in the storage pool of nitrate in shoots was related to the role of NO₃⁻ as an osmoticum.     

干旱胁迫对小麦幼苗根系生长和叶片光合作用的影响

采用水培试验方法,以2个耐旱性不同的小麦品种(敏感型望水白和耐旱型洛旱7号)为材料,研究了干旱胁迫对小麦幼苗根系形态、生理特性以及叶片光合作用的影响,以期揭示小麦幼苗对干旱胁迫的适应机制.结果表明： 干旱胁迫下,2个小麦品种幼苗的根系活力显著增大,而根数和根系表面积受到抑制;干旱胁迫降低了望水白的叶片相对含水量,提高了束缚水/自由水,而对洛旱7号无显著影响;干旱胁迫降低了2个小麦品种叶片的叶绿素含量、净光合速率、蒸腾速率、气孔导度和胞间CO2浓度,但随胁迫时间的延长,洛旱7号的叶绿素含量和净光合速率与对照差异不显著;干旱胁迫降低了2个小麦品种幼苗的单株叶面积,以及望水白的根系、地上部和植株生物量,而对洛旱7号无显著影响.水分胁迫下,耐旱型品种可以通过提高根系活力、保持较高的根系生长量来补偿根系吸收面积的下降,保持较高的根系吸水能力,进而维持较高的光合面积和光合速率,缓解干旱对生长的抑制.     

Response to drought of Zn-stressed Quercus suber L. seedlings

Zinc is an essential nutrient for higher plants but it becomes toxic as its availability increases. In nature, different stress factors commonly occur concurrently, challenging our ability to predict their impacts. Information on zinc (Zn) effect on plant ability to withstand other sources of stress is scarce. This study examines the effect of zinc supply rate on the response of Quercus suber L. seedlings to water stress. Seedlings were treated with four levels of zinc from 3 to 150 μM, and then exposed to a short severe drought. Zinc concentration in leaves and roots increased with zinc availability. Maximum photosynthetic rate, photochemical efficiency, root length and specific root length decreased as Zn availability increased. The decrease was particularly intense between 50 and 150 μM Zn. The relative effects of drought were less intense in seedlings receiving higher doses of Zn than in those receiving 3 μM. Thus, at severe drought, relative water content of detached leaves decreased to 52% in seedlings receiving the lowest level of Zn. In contrast, relative water content remained above 70% in seedlings exposed to high concentrations of this metal. The pattern was similar for photosynthetic rate and stomatal conductance, as the decrease in these variables resulting from severe drought was 100% and 90% in seedlings receiving 3 μM and 65% and 56% in seedlings receiving the highest Zn dose. Our results suggest that morpho-physiological responses to zinc may foster water conservation strategies and alleviate the effects of drought in the short term, but they may impair seedling ability to root and grow in a longer term.     

Nitric oxide treatment alleviates drought stress in wheat seedlings

The effects of sodium nitroprusside (SNP; nitric oxide donor) treatment on drought stress induced by PEG for different periods of time in wheat seedlings were investigated. Our results suggested that treatment for 2, 4 and 6 d with 15 % PEG could be termed as mild, moderate and severe stress, respectively. Drought stress induced accumulation of hydrogen peroxide and resulted in lipid peroxidation. On the other hand, activities of SOD, CAT and PAL increased under mild stress to counteract the oxidative injury and then decreased when the stress became severe (6 d). As the effect of SNP treatment, 0.2 mM enhanced wheat seedlings growth and kept high relative water content and alleviated the oxidative damage. However, 2 mM SNP aggravated the stress as a result of uncontrolled generation of reactive oxygen species and ineffectiveness of antioxidant systems.     

Response of chlorophyll fluorescence parameters to drought stress in sugar beet seedlings

We compared the parameters of chlorophyll fluorescence between two sugar beet (Beta vulgaris L.) species differing in drought tolerance. Our results indicated that there were different responses to the drought stress of these sugar beet species. In drought-tolerant sugar beet, the F ₀ increased slightly, while qN increased substantially, indicating that these plants can protect PSII reaction centers from the damage. F _v/F _m and qP decreased slightly during the initial period of drought stress; this suggests that there is a slight impact of drought stress on the openness of PSII reaction centers, and thus the plants did not suffer seriously. This was further shown by the decreased Yield and electron transfer rate. The parameters of chlorophyll fluorescence were stable and can be used as an important indicator for sugar beet seedlings in the early drought tolerance.     

Photosynthetic characteristics and enzymatic antioxidant capacity of leaves from wheat cultivars exposed to drought

Two durum (Triticum durum L.), Barakatli-95 and Garagylchyg-2; and two bread (Triticum aestivum L.) wheat cultivars, Azamatli-95 and Giymatli-2/17 with different sensitivities to drought were grown in the field on a wide area under normal irrigation and severe water deficit. Drought caused a more pronounced inhibition in photosynthetic parameters in the more sensitive cvs Garagylchyg-2 and Giymatli-2/17 compared with the tolerant cvs Barakatli-95 and Azamatli-95. Upon dehydration, a decline in total chlorophyll and relative water content was evident in all cultivars, especially in later periods of ontogenesis. Potential quantum yield of PS II (F(v)/F(m) ratio) in cv Azamatli-95 was maximal during stalk emergency stage at the beginning of drought. This parameter increased in cv Garagylchyg-2, while in tolerant cultivar Barakatli-95 significant changes were not observed. Contrary to other wheat genotypes in Giymatli-2/17 drought caused a decrease in PS II quantum yield. Drought-tolerant cultivars showed a significant increase in CAT activity as compared to control plants. In durum wheat cultivars maximal activity of CAT was observed at the milk ripeness and in bread wheat cultivars at the end of flowering. APX activity also increased in drought-treated leaves: in tolerant wheat genotypes maximal activity occurred at the end of flowering, in sensitive ones at the end of ear formation. GR activity increased in the tolerant cultivars under drought stress at all stages of ontogenesis. SOD activity significantly decreased in sensitive cultivars and remained at the control level or increased in resistant ones. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.     

Stress induced injury and antioxidant enzymes in relation to drought tolerance in wheat genotypes

The role of plant antioxidant system in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in a general increase in lipid peroxidation (LPO) and decrease in membrane stability index (MSI), and contents of chlorophylls (Chl) and carotenoids (Car). Antioxidant enzymes like glutathione reductase and ascorbate peroxidase significantly increased under water stress. Genotype C 306, which had highest glutathione reductase and ascorbate peroxidase activity, also showed lowest LPO and highest MSI, and Chl and Car contents under water stress in comparison to susceptible genotype HD 2329, which showed lowest antioxidant enzyme activity as well as MSI, Chl and Car contents and highest LPO. HD 2285 which is tolerant to high temperature during grain filling period showed intermediate behaviour. Thus, the relative tolerance of a genotype to water stress as reflected by its comparatively lower LPO and higher MSI, Chl and Car contents is closely associated with its antioxidant enzyme system. This revised version was published online in August 2006 with corrections to the Cover Date.     

Selenium improves recovery of wheat seedlings at rewatering after drought stress

Rewatering after drought is beneficial to plants subjected to moderate drought stress, and selenium (Se) could increase the tolerance of plants to stressful environment. The role of Se in rewatering of drought-treated wheat seedlings (Triticum aestivum L., cv Hengmai5229) was studied. The objective was to elucidate whether Se could improve recovery of wheat seedlings at rewatering after drought stress. Drought stress induced a significant reduction in growth parameters, total chlorophyll and soluble protein contents, and increased the rate of superoxide radical (O ₂ ^·? ) production, MDA content, and the activities of peroxidase, catalase (CAT), and superoxide dismutase in wheat seedlings. Rewatering after drought did not significantly affect biomass accumulation of seedlings over drought treatment, although it decreased the rate of O ₂ ^·? production and MDA content. However, the combined treatment of rewatering and Se evidently promoted biomass accumulation of seedlings over drought treatment and rewatering alone; and the rate of O ₂ ^·? production, MDA content, soluble protein content and CAT activity were recovered to the control values. This indicates that Se improved recovery of wheat seedlings at rewatering after drought stress.     

岳桦幼苗光合特性和非结构性碳水化合物积累对干旱胁迫的响应

以长白山林线树种岳桦为对象,利用生长控制试验进行干旱处理,研究干旱对岳桦幼苗光合特性及非结构性碳水化合物(NSC)积累的影响.结果表明:干旱显著降低了岳桦幼苗的净光合速率和气孔导度,提高了其水分利用效率;干旱显著增加了岳桦幼苗叶、皮、干和根中的可溶性糖和总NSC的含量,但显著降低了淀粉含量;随着干旱的持续,叶片的气孔导...     

A study on soybean responses to drought stress and rehydration

To investigate soybean responses to drought stress and growth through metabolism compensation after rehydration, and for the establishment of an optimal water-saving irrigation model, we used the soybean variety Suinong 14 as experimental material and adopted a weighing method for water control in potted plants. We exposed soybean plants to stress treatments at different growth stages using different stress levels and durations. We then studied the effects of drought stress and rehydration on soybean growth and development, osmoregulation, and endogenous hormonal regulations, as well as antioxidant systems. The results showed that drought stress inhibited increases in the soybean plant height and leaf area. This inhibition became more significant as the level, duration, and frequency of the drought stress increased. After rehydration, the soybean plant heights and leaf areas exhibited rapid increases and partial compensation for their decreased sizes. As the level, duration, and frequency of drought stress increased, the compensation effect decreased, but it did not return to the control level. Drought stress reduced the chlorophyll content and relative water content in the soybean leaves and increased the osmolyte contents, antioxidant potential, and peroxidation of the membrane lipids. In addition, the changes mentioned above became more dramatic as the drought stress level, duration, and frequency increased. Upon rehydration, various levels of growth compensation were observed in each physio-biochemical parameter. As the drought stress level, duration, and frequency increased, the compensation effect also increased. Overall, the compensation effect for drought stress that occurred at the early growth stages was higher than that at the later growth stages. Drought stress led to decreases in the ZR/IAA and ZR/ABA ratios in soybean leaves and an increase in the ABA/(IAA + GA + ZR) ratio; thus, the plant growth was inhibited. These hormone ratios exhibited more dramatic changes when the drought stress level became more severe and the stress duration was prolonged. After rehydration, these hormone ratios produced equal compensation effects. Therefore, the compensatory effect of rewatering after drought stress is conditional. Severe stress, especially long-term severe stress, will reduce the compensatory effect. At the same time, drought resistance treatment at seedling stage can improve the adaptability and compensatory effect of re-drought at grain filling stage.     

玉米苗期SR蛋白基因家族的干旱胁迫应答

基因表达的选择性剪接(Alternative splicing, AS)调控与植物对逆境胁迫应答密切相关, SR蛋白(Serine/ arginine-rich proteins)是其中关键的调节因子。文章对玉米B73参考基因组进行分析显示: 多数SR蛋白家族基因成员启动子区域含有3~8种与发育或胁迫相关的顺式调控元件; 27个基因成员编码碱性蛋白, 其中23个成员的编码蛋白依照其N′端的首个RRM(RNA recognition motif)结构域特征大体上可划分为5个亚组。利用双向分级聚类方法, 对三叶期干旱胁迫下玉米杂交种郑单958及其亲本郑58和昌7-2的SR蛋白基因家族的分析显示, 该基因家族的表达模式具有明显的组织表达特异性和基因型依赖性特征; 其中在干旱胁迫下地下组织以下调表达模式为主, 而地上组织中以上调表达模式为主。在重度干旱胁迫后的3个不同时段复水过程中, 地上和地下组织中SR蛋白基因家族的表达皆以下调表达模式为主。另外, 尽管不同基因成员的表达模式在干旱胁迫及其后的复水过程中存在明显差异, 但普遍存在自身选择性剪接现象。SR蛋白基因家族在玉米干旱胁迫的应答规律, 为从AS-network视角解析玉米的抗逆分子机制提供了新思路。     

木本植物水力系统对干旱胁迫的响应机制

干旱导致树木死亡对生态系统功能和碳平衡有重大影响。植物水分运输系统失调是引发树木死亡的主要机制。然而, 树木对干旱胁迫响应的多维性和复杂性, 使人们对植物水分运输系统在极端干旱条件下的响应以及植物死亡机理的认识还不清楚。该文首先评述衡量植物抗旱性的指标, 着重介绍可以综合评价植物干旱抗性特征的新参数——气孔安全阈值(SSM)。SSM越高, 表明气孔和水力性状之间的协调性越强, 木质部栓塞的可能性越低, 水力策略越保守。然后, 阐述木本植物应对干旱胁迫的一般响应过程。之后, 分别综述植物不同器官(叶、茎和根)对干旱胁迫的响应机制。植物达到死亡临界阈值的概率和时间, 取决于相关生理和形态学特征的相互作用。最后, 介绍木本植物水力恢复机制, 并提出3个亟待开展的研究问题: (1)改进叶片水分运输(木质部和木质部外水力导度)的测量方法, 量化4种不同途径的叶肉水分运输的相对贡献; (2)量化叶片表皮通透性变化, 以便更好地理解植物水分利用策略; (3)深入研究树木水碳耦合机制, 将个体结构和生理特征与群落/景观格局和过程相关联, 以便更好地评估和监测干旱诱导树木死亡的风险。     

Physiological responses of wheat seedlings to drought and UV-B radiation. Effect of exogenous sodium nitroprusside application

Physiological and biochemical responses of wheat seedlings to drought, UV-B radiation, and combined stress were investigated. Drought, UV-B, and combined stresses retarded seedling growth by 26.5, 29.1, and 55.9%, respectively. One reason for growth retardation may be the oxidative damage indicated by an increase in the H₂O₂ content and lipid peroxidation degree. Furthermore, there was negative correlation between shoot fresh weight and H₂O₂ content, fresh weight and the content of thiobarbituric acid-reacting substances (TBARS), and the positive correlation between H₂O₂ content and TBARS (R ² = 0.9251, 0.9005, and 0.9007, respectively). The activities of superoxide dismutase, guaiacol peroxidase, and ascorbate peroxidase increased under drought, UV-B, and the combination of stresses, while catalase activity decreased under the combined stress as compared to the control. The combination of drought and UV-B caused more severe damage to wheat seedlings than stress factors applied separately. Thus, the combined application of drought and UV-B had more strong adverse effects on wheat seedlings. The addition of 0.2 mM sodium nitroprusside (SNP) enhanced wheat seedling growth under drought, UV-B, and combined stress, likely, due to decreasing the accumulation of H₂O₂ and lipid peroxidation as well as activating the antioxidant enzymes. However, SNP treatment decreased the proline content. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 5, pp. 763–769. The text was submitted by the authors in English.     

Nitric oxide is involved in dehydration/drought tolerance in Poncirus trifoliata seedlings through regulation of antioxidant systems and stomatal response

Nitric oxide (NO) is a component of the repertoire of signals implicated in plant responses to environmental stimuli. In the present study, we investigated the effects of exogenous application of NO-releasing donor sodium nitroprusside (SNP) and nitric oxide synthase inhibitor N ^G-nitro-l-arginine-methyl ester (l-NAME) on dehydration and drought tolerance of Poncirus trifoliata. The endogenous NO level was enhanced by SNP pretreatment, but decreased by l-NAME, in the hydroponic or potted plants with or without stresses. Under dehydration, leaves from the SNP-treated hydroponic seedlings displayed less water loss, lower electrolyte leakage and reactive oxygen species accumulation, higher antioxidant enzyme activities and smaller stomatal apertures as compared with the control (treated with water). In addition, pretreatment of the potted plants with SNP resulted in lower electrolyte leakage, higher chlorophyll content, smaller stomatal conductance and larger photosynthetic rate relative to the control. By contrast, the inhibitor treatment changed these physiological attributes or phenotypes in an opposite way. These results indicate that NO in the form of SNP enhanced dehydration and drought tolerance, whereas the inhibitor makes the leaves or plants more sensitive to the stresses. The stress tolerance by NO might be ascribed to a combinatory effect of modulation of stomatal response and activation of the antioxidant enzymes. Taken together, NO is involved in dehydration and drought tolerance of P. trifoliata, implying that manipulation of this signal molecule may provide a practical approach to combat the environmental stresses.     

盐旱复合胁迫对小麦幼苗生长和水分吸收的影响

为明确盐害、干旱及盐旱复合胁迫对小麦幼苗生长和水分吸收的影响,从而为盐害和干旱胁迫下栽培调控提供理论依据。以2个抗旱性不同的小麦品种(扬麦16和耐旱型洛旱7号)为材料,采用水培试验,以NaCl和PEG模拟盐旱复合胁迫,研究了盐旱复合胁迫下小麦幼苗生长、根系形态、光合特性及水分吸收特性的变化。结果表明,盐、旱及复合胁迫下小麦幼苗的生物量、叶面积、总根长与根系表面积、叶绿素荧光和净光合速率均显著下降,但是复合胁迫处理的降幅却显著低于单一胁迫。盐旱复合胁迫下根系水导速率和根系伤流液强度显著大于单一胁迫,从而提高了小麦幼苗叶片水势和相对含水量。盐胁迫下小麦幼苗Na~+/K~+显著大于复合胁迫,但复合胁迫下ABA含量却显著小于单一的盐害和干旱胁迫。因此,盐旱复合胁迫可以通过增强根系水分吸收及降低根叶中ABA含量以维持较高光合能力,这是盐旱复合胁迫提高小麦适应性的重要原因。洛旱7号和扬麦16对盐及盐旱复合胁迫的响应基本一致,但在干旱胁迫下洛旱7号表现出明显的耐性。     

Effects of drought stress and selenium supply on growth and physiological characteristics of wheat seedlings

The paper studied the effects of drought stress, selenium (Se) supply and their combination on growth and physiological characteristics of wheat (Triticum aestivum L. cv Shijiazhuang NO. 8) seedlings. The experimental design included two water treatments (well-watered, 75% of maximum field capacity; drought stress, 30% of maximum field capacity) and two Se levels (0; 0.5 mg/kg) to determine whether Se can modify the negative impacts of drought stress on seedling growth and physiological traits. Drought stress caused a marked decline in growth parameters and soluble protein content, whereas it induced an increase in root activity, proline content and the activities of peroxidase (POD) and catalase (CAT) of leaf tissue. On the other hand, Se supply induced an increase in biomass accumulation only under well-watered condition. Under drought stress, Se supply increased free proline content, root activity and the activities of POD and CAT in leaf tissue, but did not significantly affect on growth parameters. These results implied that drought stress brought harmful effects on wheat seedlings, and that Se supply was favorable for biomass accumulation of wheat seedlings under well-watered condition. However, it did not significantly affect on biomass accumulation under drought stress, although it increased root activity and activities of some antioxidant index in experimental periods.