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Home Publications Climate Change / Assisted Migration Carbon isotopic composition, gas exchange, and growth of three populations of ponderosa pine differing in drought tolerance

Carbon isotopic composition, gas exchange, and growth of three populations of ponderosa pine differing in drought tolerance

Zhang, J. W., Feng, Z., Cregg, B. M., Schumann, C. M. 1997. Tree Physiology, Volume 17: 461-466
Journal Article
Development

Montana, South Dakota, USA

Effects of water supply on gas exchange, carbon isotopic composition, and relative growth rate were compared among seedlings from three populations of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) grown in a controlled environment chamber. The three populations were chosen to represent high, moderate and low drought tolerance. There was no indication that drought tolerance was related to high water use efficiency. Populations differed (P < 0.05) in relative growth rate (RGR), but did not differ (P > 0.10) in gas exchange variables or carbon isotope ratio (d13C). Well-watered seedlings had significantly higher RGR, xylem pressure potential (Yxpp), net photosynthesis (A), stomatal conductance to water vapor (g), and lower d13C and instantaneous water-use efficiency than water-stressed seedlings. With decreasing Yxpp, A decreased linearly, whereas g decreased exponentially. Seedlings of the highly drought-tolerant population were more sensitive to water availability than seedlings from the other populations; they used water quickly when water was available, but closed their stomata in response to water stress. We conclude that, in ponderosa pine, the drought avoidance mechanism is more important for survival and growth in arid and semiarid environments than the efficient use of water.