Temperature-dependence of carbon acquisition and demand in relation to shoot and fruit growth of fruiting kiwifruit (Actinidia deliciosa) vines grown in controlled environments.

Fruiting kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] vines were grown in two controlled temperatures of 28/22 and 17/12°C (day/night) for 160 and 215 d, to measure shoot and fruit growth and carbon demand, and to examine competition between fruit and the shoot. Leaf area, internode lengths, fruit diameters, photosynthesis and respiration were measured at regular intervals. The net daily carbon balance per shoot was determined from the net carbon acquisition of shoots, and carbon sequestration as shoot biomass. Vines grown at high temperature had 200% more leaf area, similar stem lengths and 100% more biomass than vines grown at low temperature. Leaf area expansion and stem extension were transiently reduced when fruit growth was maximal. Photosynthetic and respiration rates were affected by temperature, leading to net carbon acquisition of 450 g shoot-1 for 28/22°C-grown vines and 253 g shoot-1 for 17/12°C-grown vines, 54% being used for leaf, stem and fruit growth. Reallocation of carbon occurred from leaves to fruit, and the consequent reduction in leaf area strongly reduced the overall carbon balance compared with vegetative vines at similar temperatures. The data support the conclusion that at low temperatures especially, there is insufficient carbon to meet the full demands of both fruit and shoot growth.