摘要
为探讨未来降水减少对内蒙古皇甫川流域人工栽培主要灌木树种中间锦鸡儿气体交换特征的影响 ,特设计正常降雨水平、偏旱、干旱和极端干旱 4种水分处理水平 ,进行人工模拟水分胁迫实验。结果表明 ,不同的水分处理显著影响土壤含水量、土壤温度、净光合速率、气孔导度、蒸腾速率、资源利用效率和叶片水势。适度的水分胁迫 (干旱环境 )能够提高中间锦鸡儿的水分利用效率和抗旱性 ,同时也降低了净光合速率与蒸腾速率。随水分胁迫的增强 ,中间锦鸡儿的净光合速率日变化曲线逐渐从典型的单峰型转变成双峰型 ,出现光合“午睡”现象。根据 Farquhar和 Sharkey提出的判别标准 ,干旱和极端干旱下光合“午睡”的原因分别以气孔因素和非气孔因素 (叶肉细胞光合能力下降 )为主。中间锦鸡儿通过自身的生理调节以抵抗干旱 ,是其能够适应干旱环境、历经
Water availability is one of the major limits for the plant growth and development, and the way an environmental factor such as water can affect plant growth is to influence plant physiological process and conditions. The physical environment in arid and semi-arid areas may become more and more severe because of global warming and local drying. Experimental evidences for the effects of precipitation change, especially of severity of water stress, on plant individuals are important basis for further understanding interactions between ecosystems and climatic system. Caragana intermedia, a dominant planting shrub in Huangfuchuan Watershed in Inner Mongolia, survived the three-year severe droughts from 1999 to 2001, while other planted shrubs such as Hippophae rhamnoides died back then. We conducted a controlled experiment to simulate variable water stress, including normal precipitation, slight drought, drought and extreme, in order to examine the effects of the eco-physiological characteristics and eco-physiological adaptive strategies of C. intermedia under different water supply conditions. The experiment site was located at the Ecological Field Experiment Station of Beijing Normal University in Huangfuchuan Watershed (39°45.10′N, 111°07.49′E, 1 099 m), built in April 2002. One hundred and sixty of one-year-old C. intermedia seedlings of approximately the same size from the Shagedu Nursery near the Experiment Station were randomly divided into eight groups, and then were planted respectively in eight cement pools. There is an approximate 20% of precipitation as a loss in the forms of runoff and seepage under the same natural conditions according to a runoff experiment done locally. The annual average precipitation of 40 years (1961~2000) in Huangfuchuan Watershed was 389.75 mm. We use 315mm of artificial water-supply amount to simulate normal condition of annual precipitation. According to the criteria given by the National Climate Center of China, the designed water-supply levels of 315mm represent normal precipitation, marked as W4. Similarly 227.5, 167, 115mm were used for slight drought (W3), drought (W2) and extreme drought (W1) conditions respectively. A replicated group was set relative to the above different water treatments respectively. The water supply proportion of each treatment in each month of the year was determined based on the mean precipitation in each month during 1961~2000 in the study area. Soil water content and soil temperature were measured during the experimental period. Photosynthesis rate, transpiration rate, environmental factors and leaf water potential were measured on July 10, 2002. Soil temperature decreased distinctly with the increase of the water supply. Generally, soil water content increased with the water supply, but that of the highest water supply (W4), was not the largest, due to the increases in total leaf area and transpiration rate, which resulted in the significant increase in total transpiration and much excessive water consumption. Ci/Ca, an indicator of drought-resistance, implied that the moderate water stress (W2) could improve the drought-resistance ability, and furthermore, the drought-resistance ability under extreme drought was higher than those under the other two treatments. The moderate water stress could improve WUE at the cost of net photosynthetic rate and transpiration rate. As an early indicator of water stress, premature closure of stomata of C. intermedia seedlings under all water conditions from extreme drought to normal precipitation indicated that they were all affected by water stress to different extents. With increases in water stress, transpiration water loss and leaf water potential, stomatal conductance, transpiration rate and net photosynthesis rate decreased accordingly. This mechanism helps plants by avoiding the injury to mesophyll tissues under excessive water loss. Water stress reduced the net photosynthesis rate. With increases in water stress, the diurnal pattern of net photosynthetic rate shifted from a typical single-peak
出处
《生态学报》
CAS
CSCD
北大核心
2004年第12期2716-2722,共7页
Acta Ecologica Sinica
基金
国家重点基础研究发展规划资助项目 ( G2 0 0 0 0 1860 7)
教育部博士点基金资助项目 ( 2 0 0 3 0 42 2 0 3 0 )~~
关键词
模拟水分胁迫
中间锦鸡儿
气体交换
水势
资源利用效率
光合“午睡”
simulated water stress
Caragana intermedia
gas exchange
water potential
resource use efficiency
midday depression of photosynthesis
