, Volume 104, Issue 1, pp 19-30
Date: 29 Jan 2010

Temperature responses of photosynthesis and respiration in Populus balsamifera L.: acclimation versus adaptation

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Abstract

To examine the role of acclimation versus adaptation on the temperature responses of CO2 assimilation, we measured dark respiration (R n) and the CO2 response of net photosynthesis (A) in Populus balsamifera collected from warm and cool habitats and grown at warm and cool temperatures. R n and the rate of photosynthetic electron transport (J) are significantly higher in plants grown at 19 versus 27°C; R n is not affected by the native thermal habitat. By contrast, both the maximum capacity of rubisco (V cmax) and A are relatively insensitive to growth temperature, but both parameters are slightly higher in plants from cool habitats. A is limited by rubisco capacity from 17–37°C regardless of growth temperature, and there is little evidence for an electron-transport limitation. Stomatal conductance (g s) is higher in warm-grown plants, but declines with increasing measurement temperature from 17 to 37°C, regardless of growth temperature. The mesophyll conductance (g m) is relatively temperature insensitive below 25°C, but g m declines at 37°C in cool-grown plants. Plants acclimated to cool temperatures have increased R n/A, but this response does not differ between warm- and cool-adapted populations. Primary carbon metabolism clearly acclimates to growth temperature in P. balsamifera, but the ecotypic differences in A suggest that global warming scenarios might affect populations at the northern and southern edges of the boreal forest in different ways.