Photosynthetic Development in Relation to Leaf Expansion in Kiwifruit (Actinidia deliciosa) Vines During Growth in a Controlled Environment

Abstract

Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) vines were grown in constant conditions for 3 months starting from budbreak to measure relationships between leaf development and photosynthesis during leaf expansion. Leaf area, net photosynthesis and fluorescence were repeatedly measured on the same leaves at regular intervals. At the growth conditions, the vines produced 0.5 leaves per day, with the earliest expanding leaves taking about 40 days and later emerging leaves up to 70 days to expand fully. Maximum leaf area increased up to leaf 9 then declined with later emerging leaves. Photosynthesis and photochemical efficiency depended on nodal position but were both highest in the earliest emerging leaves. Maximum photosynthetic capacity of individual leaves generally occurred in concert with leaves reaching full expansion but high rates of photosynthesis were observed within 10 days after budbreak. The early expanding leaves (positions 4 to 9) contributed up to 50% of the total net shoot carbon acquisition over the study period. Young leaves were also resistant to imposed photoinhibitory stresses. Early emerging leaves on kiwifruit vines appear physiologically well adapted to provide carbon in spring, when the plants are in a negative carbon balance.