Sensitivity to Drought Stress of Three Soybean Cultivars During Different Growth Stages

Three soybean ( Glycine max L.) culivars, Lee-74, Wright , and Ra 401 , were subjected to 100 % (control), 75 %, and 50 % of field capacity during vegetative (VI), flowering (R2), and pod-filling (R4) stages in greenhouse and field studies. Stress applied at R2 significantly reduced the yield in the greenhouse, while in the field, the maximum reduction was observed when the plants were subjected to stress at R4. Stress during VI reduced the yield components less than stress applied during R2 or R4 stages in both studies. The pod number and seed weight were the yield components most affected by drought stress, and the number of seeds per pod the least affected. Yield stress index was significantly correlated with the yield and its components. The reproductive stage was clearly more sensitive to drought than the vegetative stage. The cultivar Lee 74 had the highest yield and the second highest yield stress index whereas the cultivar Ra 401 had the lowest yield.     

Effect of Water Status on Leaf Angle and Leaf Movement in Wheat

Water stress was imposed by watering withholding or application of PEG during the period following ligule emergence of Hag leaves or fifth leaves. Treatment reduced markedly the downward rotation of these youngest fully expanded leaves, and the angle finally reached. Leaf angle changes appear to be sensitive indicators of water shortage in wheat.     

Thermal Infrared Radiation for Assessing Crop Water Stress in Wheat

Field studies on differentially irrigated wheat ( Triticum aestivum L.) crops were conducted at Pantnagar for two years to evaluate the use of thermal infrared radiation to detect crop water stress. Data show that the stress-degree-day index (mid day canopy-air temperature difference) is influenced by environmental variability other than soil moisture. Improvement in the stress-degree-day (SDD) index was achieved by including the measurements of vapor pressure deficit and approach was termed as plant water stress index (PWSI). Observations indicated that daily variation in SDD values due to meteorological changes was removed through PWSI. Better correlation was found between soil-induced leaf water potential and plant water stress index than between total leaf water potential and plant water stress index. It is concluded that remote sensing of thermal infrared radiation offers a promising technique which can be incorporated into irrigation management programme.     

THE MIXED MODE FRACTURE CRITERION OF BRITTLE ROCK UNDER COMPRESSION-SHEAR STRESS STATE

In this paper the test results of mixed mode fracture of three kinds of brittle rock under two kinds of stress paths are reported. The fracture mechanism and failure patterns of brittle lock under different stress paths are discussed. Theory analysis and test results show that the Compression- Shear fracture criterion of brittle rock can be expressed:     

基于高通量测序的露地菊(Chysanthemum×grandiflora)盐胁迫转录组分析

为揭示露地菊生长发育及耐盐胁迫的应答机制和分子基础,本研究以盐胁迫处理的露地菊及其对照为材料,使用Illumina Hiseq2500高通量测序平台对转录组进行测序,分别获得了60370448和71415448条Clean reads,通过序列拼接组装得到45591条Unigene,平均长度724 bp。有37675条Unigene在七大数据库(COG,GO,KEGG,KOG,Pfam,Swiss-Prot,NR)中得到注释。通过比对露地菊盐胁迫处理组和对照组样品间Unigene的表达量及在各数据库中的注释情况,统计得到:有4143条差异表达基因获得注释;有2441条差异表达基因在GO数据库中获得功能注释;注释到COG数据库中的2281条差异表达基因依据功能可分为25类;有1062条差异基因映射到KEGGPathway数据库中,涉及了199个代谢通路,包括核糖体途径、植物激素信号传导途径、淀粉蔗糖代谢、碳代谢、氨基酸的生物合成等。本研究获得的转录组数据将有助于揭示露地菊生长发育及耐盐胁迫的应答机制和分子基础,及相关抗性基因的挖掘和分子辅助育种等方面的研究。     

水分胁迫下马铃薯基因组DNA甲基化水平变化分析

DNA甲基化是表观遗传学修饰的重要研究内容之一,在植物生长发育和响应逆境胁迫等过程中起重要作用,其中水分胁迫是对植物生长发育最具危害的逆境胁迫之一。为探索马铃薯DNA甲基化与水分胁迫之间的关系,本研究采用PEG-6000模拟水分胁迫处理两个马铃薯品种‘青薯9号’和‘大西洋’,在PEG0%(对照),5%和10%浓度下,利用MSAP技术检测‘青薯9号’和‘大西洋’甲基化水平变化情况。结果表明:在相同条件下,抗旱型品种‘青薯9号’甲基化水平高均于干旱敏感型品种‘大西洋’。在0%(对照)、5%和10%PEG胁迫下,‘青薯9号’MSAP比率为42.49%、38.14%、49.21%,甲基化水平与对照相比先降低后升高,‘大西洋’MSAP比率29.17%、22.92%、17.58%,甲基化水平逐渐降低。经统计,5%PEG和10%PEG胁迫下,‘青薯9号’和‘大西洋’均出现甲基化和去甲基化现象,其中‘青薯9号’甲基化和去甲基化比率分别为10.92%、6.43%和11.98%、15.36%,‘大西洋’分别为1.59%、8.22%和42.18%、24.34%,甲基化变异模式以去甲基化为主。‘青薯9号’和‘大西洋’均能发生CNG、CG和CG/CNG位点的甲基化和去甲基化,在水分胁迫下会产生较多的CNG和CG/CNG位点。本研究结果为探究马铃薯抗旱机制提供了理论基础。     

低温胁迫对不同品种玉米苗期根系性状的影响

盆栽试验研究了低温对不同玉米品种（农大364,先玉335）苗期根系发生发育及生物量的影响。结果表明：在低温胁迫下,玉米苗期根表面积、根体积、轴根长都明显低于常温处理。不同品种玉米总根长和侧根长对温度的反应程度存在明显差异,低温对农大364侧根生长明显促进作用,而对先玉335侧根生长有明显抑制作用。低温胁迫减弱了玉米根系的生长,同时对地上部的生长有明显的抑制作用,进而根冠比显著增大。     

开花和灌浆初期高温胁迫对国稻6号结实的生理影响

为研究杂交稻对开花结实期高温胁迫的生理生态适应性,选用具代表性的主栽杂交稻组合国稻6号、协优46,人工设计极值高温40~42℃,自始穗期至此后15 d每天6 h行热害处理,以自然气候条件为对照,比较研究高温胁迫对国稻6号与协优46结实的生理影响。结果表明,国稻6号具较高的受孕小穗成粒效应,即不仅不孕小穗率低,而且秕谷率也低。国稻6号对开花结实期高温较协优46钝感,两者在小穗育性和热害指数上的差异达到显著水平(P<0.05)。究其生理原因, (1)成熟期间稻株剑叶光能转化效率及光合效率较高,茎鞘储藏物质较丰;(2)成熟期间稻株仍具较强根系吸水能力与叶片蒸腾水平,维持蒸腾流利于光合物质运输;(3)成熟灌浆期稻株自动调节粒间顶端优势,增进迟开花的弱势粒充实成实粒。     

Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.