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柠条(Caragana korshinskii)是宁夏沙坡头地区的主要固沙灌木,建植初期表现出较强适应性,但随着年龄增长和土壤水分耗竭,开始出现衰退。为探明灌木年龄与其退化的关系,野外原位测定了不同林龄(3、13、25龄)柠条的叶水势、叶相对含水量、叶表观导水率、净光合速率及水分利用效率,分析了其光合特性与叶水势的关系。结果表明:(1)不同林龄柠条的光合能力和水分利用效率差异显著,中龄、幼龄的光合能力高于老龄,而水分利用效率低于老龄;(2)净光合速率、气孔导度与叶水势的非线性关系,反映出不同林龄柠条采取不同策略应对干旱胁迫,幼龄柠条通过快速关闭气孔来减少水分散失,而中龄和老龄柠条通过调整水分利用策略来应对干旱。老龄柠条通过提高水分利用效率来使水分利用最大化,但其植物水势和光合的降低可能导致生长减缓和衰退。
Caragana korshinskii is the main shrub-fixing shrub in Shapotou area of Ningxia. The Caragana korshinskii showed strong adaptability in early stage of planting, but began to decline with age and soil moisture depletion. In order to explore the relationship between the shrub age and its degeneration, the leaf water potential, leaf relative water content, apparent leaf water conductivity, net photosynthetic rate and water use of different ages (3, 13, 25) Efficiency, the relationship between photosynthetic characteristics and leaf water potential was analyzed. The results showed that: (1) There was significant difference in photosynthetic capacity and water use efficiency of Caragana korshinskii cultivated in different age groups. The photosynthetic capacity of middle age and young age was higher than that of old age, but the water use efficiency was lower than that of old age. (2) The net photosynthetic rate The non-linear relationship between water content and leaf water potential indicated that different strategies were adopted to deal with drought stress in different ages of Caragana korshinskii. The young Caragana korshinskii reduced the water loss by rapidly closing the stoma, while the middle-aged and aged Caragana korshinskii adjusted the water use strategies drought. Old-age krass maximizes water use by increasing water use efficiency, but the reduction of plant water potential and photosynthesis may lead to slowed growth and decline.