不同植物在水分胁迫条件下脯氨酸的累积与抗旱性的关系

Ca植物春小麦幼苗叶片累积脯氨酸的数量随水分胁迫时间和强度递增,累积的数量与品种的抗旱性没有相关性。C_4植物玉米和高粱累积脯氨酸的数量低于小麦,但高粱多于玉米。CAM植物落地生根脯氨酸含量略有变化。旱生植物细枝岩黄芪的同化枝累积脯氨酸的数量高于中生植物钻天杨和槐的叶片,而梭梭的同化校则低于槐而高于钻天杨。表明这些植物累积脯氨酸的数量与它们的抗旱性无夫。因此似不宜用脯氨酸数量的多少作为植物抗旱性的生理指标。     

Response of Eucalyptus occidentalis to Water Stress Induced by NaCl

Eucalyptus occidentalis plants were exposed to NaCl in their culture solution for various time. Determination of cytokinin, abscisic acid, ¹⁴C leucine incorporation of E. occidentalis, a xerophyte, does not differ from the response of mesophytes to such treatments.     

Recurrent Mild Drought Events Increase Resistance Toward Extreme Drought Stress

The frequency and magnitude of extreme weather events such as drought are expected to increase in the future. At present, plant responses to recurrent extreme events have been sparsely examined and the role of stress history on subsequent stress response has been widely neglected. In a long-term field experiment, we investigated the response of grassland and heath communities to a very severe drought event, which exceeded the duration of projected drought scenarios. During the preceding 6 years, the plant communities experienced scenarios of varying water supply, including annually recurring drought, heavy rain, regular watering, and natural drought periods. Single species and plant communities that were regularly watered in the preceding years revealed the highest tissue die-back under a very severe drought when compared to plants that experienced mild or severe drought stress before. Contrary to expectations, the root to shoot ratio did not increase due to previous recurrent drought occurrences. Furthermore, pre-exposure effects on Vaccinium myrtillus and Plantago lanceolata tissue die-back and reproductive biomass (P. lanceolata) were altered by community composition. Recurrent mild drought stress seems to improve drought resistance of plant communities and species. Potential reasons could be epigenetic changes or soil biotic legacies. Morphological legacies such as altered root to shoot ratio did not play a role in our study. Imprinting events which trigger this ecological stress memory do not have to be extreme themselves. Thresholds, longevity of effects, and the role of biodiversity shown by the importance of community composition require further attention.     

The Effects of Mechanically-induced Stress on Water Loss and Drought Resistance in Lettuce, Cauliflower and Celery Seedlings

Lettuce, cauliflower and celery seedlings brushed with paperfor 1–5 min each day for several days, were smaller thanunbrushed control seedlings, and, most notably with lettuce,recovered less well from periods of drought. One reason forlowered drought resistance may have been an increased transpirationrate per unit leaf area measured in brushed seedlings comparedto controls. Further experiments with lettuce seedlings showeda greater density of stomata on the leaf surface of brushedseedlings compared with untreated ones.     

Bound Water in Durum Wheat under Drought Stress

To study drought stress effects on bound water, adsorption isotherms and pressure-volume curves were constructed for two durum wheat (Triticum durum Desf.) cultivars: Capeiti 8 (drought tolerant) and Creso (drought sensitive). Plants were grown under well-watered and water-stressed conditions in a controlled environment. Differential enthalpy (ΔH) was calculated through van't Hoff analysis of adsorption isotherms at 5 and 20°C, which allowed us to determine the strength of water binding. ΔH reached the most negative values at approximately 0.06 gram H₂O/gram dry weight and then increased rapidly for well-watered plants (until 0.10 gram H₂O/gram dry weight) or more slowly for drought-stressed plants (until 0.15-0.20 gram H₂O/gram dry weight). Bound water values from pressure-volume curves were greater for water-stressed (0.17 gram H₂O/gram dry weight) than for well-watered plants (0.09 gram H₂O/gram dry weight). They may be estimates of leaf moisture content where ΔH reaches the less negative values and hence some free water appears. With respect to the well-watered plants, tightly bound water tended to be less bound during drought, and more free water was observed in cv Creso compared to cv Capeiti 8 at moisture contents >0.10 gram H₂O/gram dry weight.     

转ZjAPX基因拟南芥对NaCl、干旱胁迫的耐性研究

旨在探讨枣树抗坏血酸过氧化物酶基因ZjAPX在植物渗透胁迫中的作用。将ZjAPX基因转入到模式植物拟南芥,以野生型(WT)、转ZjAPX拟南芥株系T2为试材,进行不同浓度NaCl胁迫和干旱胁迫。结果表明,转基因株系的种子萌发、植株生长均优于野生型株系;荧光定量PCR检测转基因拟南芥植株在干旱和盐胁迫处理10 d后目的基因ZjAPX的表达量显著高于野生拟南芥,表明ZjAPX的高表达明显提高了植株的抗旱和耐盐性。     

Transgenerational Variations in DNA Methylation Induced by Drought Stress in Two Rice Varieties with Distinguished Difference to Drought Resistance

Adverse environmental conditions have large impacts on plant growth and crop production. One of the crucial mechanisms that plants use in variable and stressful natural environments is gene expression modulation through epigenetic modification. In this study, two rice varieties with different drought resistance levels were cultivated under drought stress from tilling stage to seed filling stage for six successive generations. The variations in DNA methylation of the original generation (G0) and the sixth generation (G6) of these two varieties in normal condition (CK) and under drought stress (DT) at seedling stage were assessed by using Methylation Sensitive Amplification Polymorphism (MSAP) method. The results revealed that drought stress had a cumulative effect on the DNA methylation pattern of both varieties, but these two varieties had different responses to drought stress in DNA methylation. The DNA methylation levels of II-32B (sensitive) and Huhan-3 (resistant) were around 39% and 32%, respectively. Genome-wide DNA methylation variations among generations or treatments accounted for around 13.1% of total MSAP loci in II-32B, but was only approximately 1.3% in Huhan-3. In II-32B, 27.6% of total differentially methylated loci (DML) were directly induced by drought stress and 3.2% of total DML stably transmitted their changed DNA methylation status to the next generation. In Huhan-3, the numbers were 48.8% and 29.8%, respectively. Therefore, entrainment had greater effect on Huhan-3 than on II-32B. Sequence analysis revealed that the DML were widely distributed on all 12 rice chromosomes and that it mainly occurred on the gene’s promoter and exon region. Some genes with DML respond to environmental stresses. The inheritance of epigenetic variations induced by drought stress may provide a new way to develop drought resistant rice varieties.     

用渗透胁迫鉴定小麦种子萌发期抗旱性的方法分析

本以聚乙二醇(PEG)-6000、甘露醇和蔗糖作为渗透剂模拟水分胁迫,胁迫溶液渗透势范围在-0．25MPa到-1．50MPa,分析适于进行小麦种子水分胁迫萌发试验的条件,以鉴定小麦萌发期的抗旱性。结果表明,蔗糖溶液易诱发霉茵,胚芽不能正常生长。渗透势为-0．25MPa的PEG-6000及-0．50MPa的甘露醇胁迫已经显抑制了胚芽伸长;-0．50MPa的PEG-6000及-1．00MPa的甘露醇显抑制种子萌发,随着胁迫强度增加,种子相对发芽率及胚芽长度减小,主要是因为渗透胁迫降低了种子吸水速度,胚芽的相对含水量和渗透势均低。在渗透势相同的胁迫条件下,PEG-6000对小麦种子萌发各项检测值的抑制作用均大于甘露醇。如果目的是通过鉴定小麦种子在高渗溶液中的萌发情况,评价萌发期的抗旱性。选用-0．50MPa的PEG-6000或-1．00MPa的甘露醇较为理想,若同时考虑降低试验成本,则应首选-0．50MPa的PEG-6000。     

水分胁迫对冬小麦CO_2同化作用的影响

比较了两个小麦品种陕合6号和郑引1号经受不同程度的水分胁迫处理后,叶片多种光合参数:净光合速率(P_n)、气孔导度(G_s)、细胞间隙CO_2浓度(G_i)、表观量子需要量和羧化效率以及Rubis CO蛋白量与活性等的变化。在轻度水分胁迫下,叶片光合速率降低的根本原因在于气孔导度的下降;而在严重胁迫下,非气孔因素起主要作用。     

干旱胁迫对不同抗旱性棉花品种抗氧化酶活性及基因表达的影响

为明确不同抗旱性棉花品种对干旱胁迫的适应性差异,该研究选用‘新陆早50号’(耐旱型)和‘新陆早27号’(干旱敏感型)为材料,分析干旱及复水处理下两材料的活性氧产生、电解质渗漏、抗氧化酶活性变化,并分析部分抗氧化酶基因、渗透调节基因和转录因子在干旱胁迫下的表达谱。结果显示:(1)棉花叶片的电导率和MDA含量随着干旱胁迫的加强逐渐增加,复水后恢复;在干旱胁迫处理6和8d,耐旱型品种‘新陆早50号’的抗氧化酶活性显著高于干旱敏感型品种‘新陆早27号’。(2)基因表达谱分析显示,棉花超氧化物歧化酶基因(GhSOD)仅在干旱胁迫下表达,且2个品种间差异不显著,GhBADH、GhNCED和GhP5Cs及转录因子GhPHD1、GhPHD5、GhPHD6和GhPHD10在‘新陆早50号’叶片中的表达量均高于‘新陆早27号’。研究表明,耐旱型棉花品种较干旱敏感型在干旱胁迫下其体内的活性氧含量、电导率和MDA含量较低,抗氧化酶活性较高,并且其抗旱相关基因表达量也更高。     

3种荒漠植物光合及叶绿素荧光对干旱胁迫的响应及抗旱性评价

利用盆栽试验结合人工浇水后自然耗水的方法测定干旱胁迫对梭梭、白刺、沙蒿3种荒漠植物叶片水分、光合及叶绿素荧光参数的影响,探讨各指标在干旱胁迫过程中的变化特征、响应机制及其与土壤水分的定量关系,并用隶属函数法对其进行抗旱性排序。结果表明：(1)3种植物叶片相对含水量(RWC)随干旱胁迫天数增加持续降低,最大水分亏缺(RWD)呈波动式上升趋势。(2)3种植物总叶绿素含量(Chl)和叶绿素a(Chla)、叶绿素b(Chlb)含量,以及梭梭、白刺类胡萝卜素含量均随胁迫天数增加而降低;沙蒿类胡萝卜素随土壤含水率降低逐渐升高。(3)梭梭、白刺、沙蒿叶片净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)等主要光合气体交换参数对土壤水分表现出明显的阈值响应,适宜的土壤含水率分别为8.04%～19.33%、4.17%～19.10%、6.48%～17.51%。(4)3种植物 PSⅡ最大光化学效率(Fv/F_m)、实际光化学效率(F_v′/F_m′)及光化学淬灭系数(qP)均随干旱胁迫天数增加和光照强度增大而降低,非光化学淬灭系数(NPQ)则呈逐渐上升趋势;干旱胁迫中后期,梭梭、沙蒿的F_v/F_m及F_v′/F_m′均下降,光合机构光合活性遭到破坏,电子传递受阻,PSⅡ反应中心受损,表现出光抑制,而白刺调节自身PSⅡ反应中心免受伤害的能力较强。(5)隶属函数法综合分析表明,3种植物耐旱能力大小依次为白刺>梭梭>沙蒿。研究发现,3种荒漠植物均可通过调节 PSⅡ反应中心开放程度与活性,对干旱胁迫表现出较强的耐性,胁迫后期植物PSⅡ反应中心关闭或不可逆失活,表现出光抑制。     

Interactions of Elevated CO2 Concentration and Drought Stress on Photosynthesis in Eucalyptus Cladocalyx F. Muell

Response of net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (c _i), and photosynthetic efficiency (F_v/F_m) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C₈₀₀) or 380 (C₃₈₀) µmol mol^-1 CO₂ concentration under sufficient water supply or under water stress. The well-watered plants at C₈₀₀ showed a 2.2 fold enhancement of P _N without any change in g _s. Under both C₈₀₀ and C₃₈₀, water stress decreased P _N and g _s significantly without any substantial reduction of c _i, suggesting that both stomatal and non-stomatal factors regulated P _N. However, the photosynthetic efficiency of PS2 was not altered.     

Water and Osmotic Potentials of Ethephon-Treated Maize Genotypes Varying in Drought Resistance

Leaves of drought-resistant and drought-sensitive genotypes of maize (Zea mays L.) were sprayed with ethephon to determine its effect on water and osmotic potentials. With both sufficient and limited water supplies, ethephon decreased the water potential, but not the osmotic potential, of the drought-sensitive maize. It had no effect on the water and osmotic potentials of the drought-resistant maize under either water regime. The results showed that the response of a genotype of maize to ethephon depends upon its susceptibility to drought.     

Interactions of Elevated CO2 Concentration and Drought Stress on Photosynthesis in Eucalyptus Cladocalyx F. Muell

Response of net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (c _i), and photosynthetic efficiency (F_v/F_m) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C₈₀₀) or 380 (C₃₈₀) μmol mol^-1 CO₂ concentration under sufficient water supply or under water stress. The well-watered plants at C₈₀₀ showed a 2.2 fold enhancement of P _N without any change in g _s. Under both C₈₀₀ and C₃₈₀, water stress decreased P _N and g _s significantly without any substantial reduction of c _i, suggesting that both stomatal and non-stomatal factors regulated P _N. However, the photosynthetic efficiency of PS2 was not altered. This revised version was published online in June 2006 with corrections to the Cover Date.     

转AhNCED1基因拟南芥的形态特征和抗旱性研究

目的：探讨外源基因花生NCED1（AhNCED1）对拟南芥的形态特征和抗旱能力的影响。方法：观察转AhNCED1拟南芥的表型特征以及在干旱条件下的变化,利用扫描电镜观察植株叶上表面细胞和气孔大小。结果：与野生型相比,AhNCED1转基因植株矮壮,株型紧凑,分蘖和分枝数减少,幼苗根发育好。在干旱条件下转基因型植株叶大色绿,气孔开度减小,表皮细胞排列紧密。结论：转基因型植株在干旱条件下的表型特征与抗旱能力表明转基因拟南芥抗旱能力高于野生型。     

Root Xylem Influence on the Water Relations and Drought Resistance of Rice

In order to determine the importance of root axial resistanceto water flow for drought resistance of rice (Oryza sativa L.)aseries of glasshouse and growth chamber studies was conductedfrom 1985 to 1986. A preliminary study surveyed root distributionand histological characteristics of six cultivars grown in aerobicsoil (20x20x90cm boxes) under well–watered ormoisturedeficit conditions. Subsequently, four experiments were conductedwith plants grown in culture solution. Our results demonstratethat plant breeders can use root thickness as a selection indexfor xylem size for root diameters up to about 1–2 mm.Usingthe Poiseuille–Hagen Law for water movement in capillaries,rice root axial resistance explained differences in leaf waterpotential and transpiration when only one cultivar was used,but did not explain differences among cultivars. Thus, increasingroot xylem vessel radii probably will not directly increasedrought resistance. Key words: Rice (Oryza sativa), roots, xylem characteristics, drought resistance     

CPPU提高柚树苗抗旱性的研究

水分胁迫下,柚树苗叶片RWC、ψw、Pn及可溶性蛋白质,叶绿素含量下降,游离脯氨酸、MDA含量及SOD活性升高,CAT活性先上升后下降,APX活性、AsA和GSH含量明显下降,抗旱性强的品种具有较高的活性氧清除能力。CPPU处理提高柚树苗叶片RWC、Pn、叶绿素、游离脯氨酸、AsA、GSH含量,并增加SOD、APX活性,降低MDA水平,从而提高柚树苗抗旱性。实验结果表明,CPPU处理提高叶片对膜脂过氧化作用的保护能力可能是其提高柚树苗抗旱性的原因。     

干旱胁迫对水稻水分利用效率的影响

通过特殊自然干旱胁迫的方法,研究不同干旱胁迫对水稻的水分利用效率（ＷＵＥ）的影响,在一定供水量时,水稻的ＷＵＥ随供水量的增加而下降,但水稻旱种时,却因供水量过低,干旱胁迫严重,ＷＵＥ值为最低。不同品种的水稻ＷＵＥ存在较大的差异,抗旱性强的品种具有较高ＷＵＥ,因此选用具有较高ＷＵＥ的品种,是水稻节水栽培的关键。