Acclimation of Photosynthetic and Respiratory Carbon Dioxide Exchange to Growth Temperature in Atriplex lentiformis (Torr.) Wats.

Atriplex lentiformis plants collected from coastal and desert habitats exhibit marked differences in capacity to adjust photosynthetic response to changes in growth temperature. Plants from desert habitats grown at 43 C day/30 C night temperatures had higher CO(2) uptake rates at high temperatures but reduced rates at low temperatures as compared to plants grown at 23 C day/18 C night temperatures. In contrast, growth of the coastal plants at high temperatures resulted in markedly reduced photosynthetic rates at all measurement temperatures.Leaf conductances to CO(2) were not important in controlling either the differences in the temperature dependence of net CO(2) uptake or the differences in photosynthetic capacities at any measurement temperature. At low measurement temperatures, differences in photosynthetic capacities among plants acclimated to the contrasting growth regimes were correlated with differences in leaf ribulose diphophate carboxylase activities. At high measurement temperatures, the improved net photosynthetic performance of the high temperature acclimated desert plants appeared to be due to a combination of decreased respiration rates, decreased temperature dependence of respiration, and an apparent increased thermal stability of photosynthetic CO(2) exchange.