Age-related changes in photosynthesis and water relations of revegetated Caragana korshinskii in the Tengger desert, Northern China
2015
Bao, Jing-Ting | Wang, Jin | Li, Xin-Rong | Zhang, Zhi-Shan | Su, Jie-Qiong
KEY MESSAGE : Age-related declines in photosynthesis and water potentials of revegetated Caragana korshinskii in arid desert regions are likely related to both reduced soil water availability and increased hydraulic resistance in xylem. In addition to soil water depletion, the degradation of revegetated sand-binding shrubs may be attributed to specific biological traits of the plant itself, such as aging. To improve our understanding of the physiological basis of observed age-related changes in photosynthetic capacity and water relations in drought-stressed xerophytic shrubs, we conducted in situ field experiments on juvenile, young-mature and relatively old-growth Caragana korshinskii Kom. during the 2013 growing season. Our results revealed significant age-related changes in gas exchange and water-use characteristics, including decreases in the rates of photosynthesis and transpiration, stomatal conductance, shoot water potential and leaf relative water content and increase in water use efficiency with increasing age. We also found that the gas exchange and water relations of all three age classes of C. korshinskii were similarly and significantly affected by soil and atmospheric water availabilities. We conclude that the age-related changes in photosynthetic capacity and water relations which occur in C. korshinskii are likely related to reduced soil water availability and increased hydraulic resistance in xylem, both of which result in a decline in water potential, stomatal conductance and photosynthetic capacity with increasing age of the shrub.
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