Comparison of carbon economy during leaf development between shrt-lived and long-lived leaves

Abstract

The leaf construction cost on dry mass shows quite similar value among growth forms such as annual herbs and evergreen trees. During leaf development of evergreen trees, net photosynthetic rate on leaf area basis is close to zero at full leaf area expansion (FLE), and continues to increase for 10-30 days thereafter. This is contrasted with that net photosynthetic rate on leaf area basis maximizes at FLE in most annual herbs. The leaf construction cost needs to be studied in the light of leaf ontogeny. We used Phaseolus vulgaris and Quercus glauca, an evergreen broad-leaved tree. We surveyed light-photosynthetic rate relationships for estimating daily leaf glucose gain, construction cost and leaf anatomy (mesophyll and chloroplast surface areas on leaf area basis) throughout their leaf development. The transition from heterotrophic to autotrophic phase was about 9 days after full leaf area expansion in Q. glauca, which was 20 days later than that in P. vulgaris. In Q. glauca, 60% of glucose of leaf construction cost originated from remobilized substances accumulated in roots, stems and old leaves. In P. vulgaris, the value was only about 30%. In Q. glauca, chloroplast surface area was still low at FLE and increased thereafter, while mesophyll surface area showed the maximum value at FLE. These results suggest that development of chloroplasts is slower than that of mesophyll cells, and mesophyll cell development depends largely on remobilized substances in evergreen trees.