Effects of Water Stress on Stay Green of Sugarcane Innovative Materials Yunge F_2 Generation

[Objective] This study aimed to investigate the effect of water stress on stay green of Yunge F2 generation. [Method] Total 26 sugarcane innovative germplasm materials of Yunge F2 generation, along with their female parent, were selected as the experimental materials. Based on the observation on appearance of stray green and other five physiological and biochemical indexes, the drought resis- tance of the experimental materials was evaluated comprehensively by subordinate function method, grey relational analysis, and cluster analysis. [Result] The rank of drought resistance of the experimental materials was not exactly the same between subordinate function method and grey relational analysis. However, the drought .re- sistance evaluation results by isometric range-based cluster analysis were consistent with those by the two foregoing methods except Yunge F2 11-68 and Yunge F1 11- 254. At the Euclidean distance of 2.00, the tested materials were classified into four groups. The first group included 8 drought-strongly resistant materials, the third group included 6 drought-moderately resistant materials, the fourth group included 3 drought-poorly resistant materials, and the second group included drought-strongly resistant and drought-moderately resistant materials. The drought resistance coeffi- cients of green leaf numberLtotal leaf number and top four leaves chlorophyll content showed significantly positive correlation with drought resistance comprehensive eval- uation value, thus green leaf number/total leaf number and top four leaves chloro- phyll content could be used as the evaluation indexes of drought resistance in sug- arcane. [Conclusion] The excellent materials possess strong drought resistance and good green holding performance, such as Yunge F2 11-159, can be used as crucial parents and basic germplasm materials in drought resistance breeding of sugarcane. 7

环境要素变化对于渔业的风险评价及应对策略

水质环境对于水产养殖业的来说是基础性因素,诸多因子在养殖过程中起到关键作用。文章从能构成环境胁迫的溶氧、外源化学毒素及水体富营养化等环境要素变化入手,探讨各种环境胁迫因子对于水产养殖所产生的风险及其最优解决方案,为水产绿色健康养殖未来发展提供理论参考。

Effects of Different NH_4^+/NO_3^- Ratio and Water Condition on Physiological Characteristics of Rice Seedlings

[Objective] This study aimed to further explore the dynamics of related physiological indexes of rice seedlings under different NH4＋ /NO3- ratio and different water condition. [Method] Under the hydroponic condition in laboratory, 3 NH4＋/NO3- ratios （0/100, 50/50 and 100/0） and 2 water conditions （＋PEG,-PEG） were designed for Fengliangyou 7203. [Result] The root-canopy ratio of rice seedlings increased under any of the NH4＋/NO3- ratios and water conditions. Under water stress, the root-canopy ratio of rice seedlings changed most greatly at the NH4＋/NO3- ratio of 0/ 100; the overall water potential of rice seedlings reached the lowest at the NH4＋/ NO3- ratio of 100/0; and the changes of water potential and xylem flow pH were relatively stable at the NH4＋/NO3- ratio of 50/50. Under the condition of no water stress, the growth of rice seedlings was best at the NH4＋/NO3- ratio of 50/50, followed by the NH4＋/NO3- ratios of 0/100 and 100/0. [Conclusion] This study will pro- vide a basis for understanding the relationship between water potential and xylem flow.

Effect of Water Stress Caused by PEG 6000 on Germination and Seedling Growth of Four Soybean Cultivars

Soybean [Glycine max （L.）] is one of the most important protein and oil seed crop. In attention to time consuming and effect of uncontrolled agents like soil elements and hemisphere, study of tolerance in soybean to water stress during germination was investigated. Four soybean cultivars ＇Williams, Linford, L 17 and M7＇ were screened for drought tolerance by treatment of PEG6000 concentration for induce osmotic potentials （0, -3, -6, -9 bar）. A factorial experiment based on completely randomized design with three replications was conducted. Germination percentage, radicle and hypocotyls length, fresh and dry weight of radicle, hypocotyl and seedling, TWC%, MDG, rate of daily germination and percentage of abnormal seedling were measured. Variance analysis of data indicated that difference between osmotic potential had significant effect on all parameters except germination percentage. A significant reduction in fresh weight of radicle and seedling, percentage of abnormal seedlings was observed for the genotypes as the concentration of PEG increased. In interaction between cultivars and water stress level, Linford and M7 with less damage had the highest yield in fresh and dry weight of radicle, respectively. Drought is one of the most important abiotic limited potential in germination and primary growth on these cultivars.

Study of Water Relations and Solutes Accumulation in Two Rice Genotypes under NaCI Stress during Seedling Stage

In order to study osmotic adjustment and accumulation of anions and cations in rice （Oryza sativa L.） seedlings under NaCl stress, a greenhouse experiment was conducted using two rice cultivars including IR651 （tolerant） and IR29 （sensitive）. Seedlings were grown in Youshida nutrient solution. Salinity treatments were imposed 21 days after sowing with 0 and 100 mM NaCI and seedlings were harvested 0, 72, 120 and 240 hour after salinization. Water （ψw） and osmotic （ψs） potentials, total soluble sugars and inorganic ions （Na＋. K＋, Cl-, Ca2＋ and Mg2＋） concentrations and osmotic adjustment were determined in sixth （youngest） leaf. Salinity caused a substantial biomass reduction in rice seedlings, ψs reduction in IR29 was occurred more than IR651. Water potential decreased in both the cultivars under stress conditions, but IR651 was able to maintain higher ψw and kept better growth till the end of the experiment. Osmotic adjustment was observed in IR651 was about 10 times more than in IR29. K＋ accumulation decreased in both cultivars under stress condition while Na＋ accumulation increased in both the cultivars with higher increase in IR29 seedlings. CI concentration increased in youngest leaf of both IR29 and IR651. Our results showed that tolerant cultivar was able to make osmotic adjustment faster than the sensitive cultivar using high accumulation of solutes especially total soluble sugars.

Water deficit and cold stress on the evening primrose seed quality

Evening primrose is a valuable oilseed crop with pharmaceutical and nutritional supplementation. Due to presence of valuable and rare gamma linolenic fatty acid, research on this plant has been started since 1970s by German and Britain scientists. Information about evening primrose cultivation is going to rise. Following to pervious studies the goal of this experiment was to clarify the effect of water and temperature stresses on seed yield and seed quality. Results showed that seed yield was significantly influenced by low temperature and water deficit. Plants grown under cold stress during rosette stage produced a lower seed yield than controls. The lowest seed yield was observed in the plants grown under permanent stress. Although the oil content of seeds was not influenced by low temperature stress, water stress strongly influenced the oil content and water stress stimulates oil accumulation. Like oil content, the GLA production seems to be increased under water stress conditions.

Recent leveling off of vegetation greenness and primary production reveals the increasing soil water limitations on the greening Earth

Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness into sustained greening,sustained browning and greening-to-browning.We found that by 2016,increased global vegetation greenness had begun to level off,with the area of browning increasing in the last decade,reaching 39.0 million km^(2)(35.9%of the world’s vegetated area).This area is larger than the area with sustained increasing growth(27.8 million km^(2),26.4%);thus,12.0%±3.1%(0.019±0.004 NDVI a^(-1))of the previous earlier increase has been offset since 2010(2010–2016,P<0.05).Global gross primary production also leveled off,following the trend in vegetation greenness in time and space.This leveling off was caused by increasing soil water limitations due to the spatial expansion of drought,whose impact dominated over the impacts of temperature and solar radiation.This response of global gross primary production to soil water limitation was not identified by land submodels within Earth system models.Our results provide empirical evidence that global vegetation greenness and primary production are offset by water stress and suggest that as global warming continues,land submodels may overestimate the world’s capacity to take up carbon with global vegetation greening.