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排序方式: 共有1043条查询结果,搜索用时 15 毫秒
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Manzer H. Siddiqui Mutahhar Y. Al-Khaishany Mohammed A. Al-Qutami Mohamed H. Al-Whaibi Anil Grover Hayssam M. Ali Mona S. Al-Wahibi Najat A. Bukhari 《International journal of molecular sciences》2015,16(5):10214-10227
Drought stress is one of the major abiotic stresses that are a threat to crop production worldwide. Drought stress impairs the plants growth and yield. Therefore, the aim of the present experiment was to select the tolerant genotype/s on the basis of moprpho-physiological and biochemical characteristics of 10 Vicia faba genotypes (Zafar 1, Zafar 2, Shebam, Makamora, Espan, Giza Blanka, Giza 3, C4, C5 and G853) under drought stress. We studied the effect of different levels of drought stress i.e., (i) normal irrigation (ii) mild stress (iii) moderate stress, and (iv) severe stress on plant height (PH) plant−1, fresh weight (FW) and dry weight (DW) plant−1, area leaf−1, leaf relative water content (RWC), proline (Pro) content, total chlorophyll (Total Chl) content, electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H2O2) content, and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) of genotypes of faba bean. Drought stress reduced all growth parameters and Total Chl content of all genotypes. However, the deteriorating effect of drought stress on the growth performance of genotypes “C5” and “Zafar 1” were relatively low due to its better antioxidant enzymes activities (CAT, POD and SOD), and accumulation of Pro and Total Chl, and leaf RWC. In the study, genotype “C5” and “Zafar 1” were found to be relatively tolerant to drought stress and genotypes “G853” and “C4” were sensitive to drought stress. 相似文献
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Christopher P. Kofron 《Lakes & Reservoirs: Research and Management》2019,24(2):190-194
The Dune Lakes comprise 10 natural lakes in the Callender Dunes in central coastal California, USA. These lakes are wetlands in an arid environment, being important habitat for native wildlife and plants, including three occurrences of the federally endangered/State threatened wetland plant, La Graciosa thistle (Cirsium scariosum var. loncholepis; Asteraceae). This plant is known from 21 occurrences, of which only five are extant in 2019. One extant occurrence persists at the lakes and where two other occurrences are likely extirpated. Nine lakes have recently dried, one having been dry for 5 years (2012–2017). Understanding the hydrology of the Dune Lakes is essential for conservation planning and to help prevent extinction of La Graciosa thistle. The best available information points to a combination of two primary causes for drying of the lakes. The first is extensive groundwater extraction beneath Nipomo Mesa to the east. The second is severe drought. The competing demands for water and continued development on the mesa will be obstacles to restoration of the lakes and to recovery of the endangered plant. 相似文献
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为分析长江流域上游干旱特征,利用1961年1月至2012年12月长江上游共69个气象站的气象数据资料,以帕尔默干旱指数(PDSI)为主要指标对长江上游流域的干旱强度、干旱持续时间、干旱频率等干旱特征进行比较分析。结果表明,长江上游区域PDSI的月际变化较大,旱涝期交替出现,同时年代干旱最强值呈现先减弱后增强的趋势,并在2006年达到干旱强度最强值;干旱持续时间较长的干旱事件主要发生在1960、1970年代,平均干旱持续月数为4.2个月;上游干旱频率主要以初始干旱为主,其中年际干旱集中在1960年代末期至1970年代初期和2000年代后期两个阶段,季节干旱主要发生在冬季。研究成果可为长江流域上游的干旱治理提供参考。 相似文献
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以汾河上游四个水文站月径流资料为基础,选取常用的六种概率分布拟合了月、季、年时间尺度下的径流量,并进行了拟合优度检验,判断出汾河上游水文站不同时间尺度下径流服从的最佳分布函数,根据最佳分布函数计算标准化径流指数,分析不同时间尺度下的水文干旱时空变化特征。结果表明,汾河上游不同站点在不同时间尺度下服从的概率分布并不统一;不同时间尺度下四个水文站的标准化径流指数变化具有较好的一致性;1956~2000年标准化径流指数总体呈下降趋势,水文干旱逐年加重;西北部干旱程度逐渐减轻,东南部干旱严重程度逐渐加重。 相似文献
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The transfer of sediments through the landscape (sediment connectivity) depends on hydrological conditions. This study aimed at assessing changes in sediment sources engendered under extreme drought. A sediment budget model that considered hillslope sediment connectivity was applied to the Latrobe River catchment (South-east Australia) in a relatively normal period (1990–1996) followed by part of the ‘Millennium Drought’ (1997–2005). Bayesian inference was applied to optimize monthly streamflow and calibrate sediment parameters against mean annual specific sediment yields at ten monitoring stations. In 1990–1996, assessed sediment yield at the outlet was 68 kt/y; 60% of sediments originated from net hillslope erosion and 40% from streambank erosion. In 1997–2005, sediment yield decreased to 13 kt/y, 27% from net hillslope erosion against 65% from streambank erosion. During the drought, both hillslope gross erosion and hillslope sediment connectivity decreased dramatically. Streambank protection is of the utmost importance under all hydrologic conditions and especially during drought periods. 相似文献
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In this study, the Palmer Drought Severity Index (PDSI) was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America: a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nina event was considered during 1997-2003. 相似文献
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The spatiotemporal variations of the site and regional droughts in China during 1960-2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in mainland China. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Yellow River, droughts mainly occur during the winter and during May-June. During the past 50 years, the geographical distribution of site drought events showed high frequencies (0.9-1.3 times per year) in the upper Yellow River basin and North China, comparing with moderate frequencies (0.6-0.9 times per year) in Southwest China and the southwestern part of Northeast China and with lower frequencies over the middle and lower Yangtze River basin. And the frequencies increased over mainland China except for the upper reaches of the Yangtze River. A regional drought (RD) event is a widespread and persistent event that covers at least five adjacent sites and lasts for at least 10 days. There were 252 RD events in the past 50 years-five times per year. Most RD events lasted for <100 days and covered <100 stations, but the longest and largest RD event lasted for 307 days from 6 September 1998 to 9 July 1999 and covered 327 stations from North to Southwest China. 相似文献