Effects of elevated CO(2) on growth and chloroplast proteins in Prunus avium.

To predict the future carbon sequestering capacity of trees, we need information about the possible acclimatory mechanisms of plant growth and photosynthesis in rising atmospheric CO(2) under a variety of environmental conditions. We have, therefore, studied the growth response of a tree species (Prunus avium L. Stella (wild cherry)) to elevated CO(2) and characterized the associated changes in photosynthetic machinery of the leaf tissue. Self-pollinated seedlings and mature cuttings (clones) from the same parent plant of P. avium were grown for two consecutive growing seasons (about 60 days each) in ambient CO(2) (350 micro mol mol(-1) CO(2)) or elevated CO(2) (700 micro mol mol(-1) CO(2)) with a high or low nutrient supply. The degree of acclimation of leaf biochemistry and growth response to elevated CO(2) was dependent on the plant material (seedling or mature cutting) and nutrient supply. There was little or no growth response to elevated CO(2) in seedlings or cuttings in the low nutrient supply treatments, whereas, in both seasons, there was a strongly positive growth response to elevated CO(2) in seedlings and cuttings in the high nutrient supply regimes, resulting in increases in the root/shoot ratio and in carbon allocation to the roots. In contrast, the protein content and activity of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco, EC 4.1.1.39) were down regulated in elevated CO(2). The loss of Rubisco on an area basis in plants in the elevated CO(2) treatments was compensated for at the canopy level by increased leaf area. The loss of Rubisco protein was accompanied by decreases in the contents of chlorophyll and the thylakoid membrane proteins D(1), D(2) and cytochrome f, which are involved in light harvesting and photo-electron transport. We conclude that, in the medium- to long-term, the initial stimulation of biomass production by elevated CO(2) may be increasingly offset by a lower photosynthetic capacity per unit leaf area in perennial plants.