Leaf age and photosynthesis in Vitis vinifera L

The photosynthetic activity of individual vine leaves was measured on potted plants grown out doors, using both infrared C02 analysis and 14C02 fixation techniques. Peak photosynthetic activity occurred at the time when the leaf became fully expanded, approximately 40 days after unfolding. Thereafter, photosynthesis declined gradually. The increase in photosynthesis during leaf expansion was not attributable to increased chlorophyll concentration, altered spectral characteristics, or to any outstanding anatomical change. Nevertheless, a sensecent leaf was readily distinguished anatomically from an expanding or mature leaf.Irrespective of leaf age, sucrose was the major 14C02 fixation product. Oligo- saccharides also incorporated label, and accounted for a higher proportion of the 14C fixation products in older leaves. Regardless of leaf age, malic and citric acids became labelled, but the formation of 14C tartaric acid was restricted to the rapidly expanding foliage. The amino compounds serine and aspartic acid showed some incorporation of label in all leaves examined.
VITIS - Journal of Grapevine Research, Vol. 9 No. 2 (1970): Vitis