From controlled environments to field simulations: leaf area dynamics and photosynthesis of kiwifruit vines (Actinidia deliciosa)

Canopy leaf area development and daily rates of carbon acquisition of kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] vines growing in orchard conditions were modelled from mathematically-based physiological descriptions of leaf area expansion and photosynthesis of individual leaves Model drivers were temperatures and photon flux densities (PFD) measured in the orchard at 30-min intervals over the growing season. A modelling framework of shoot leaf area expansion, developed from controlled environment studies, was extended to whole vines by including canopy architectural components, such as shoot numbers, percentage budbreak and proportions of shoots in different length classes. Daily photosynthesis was modelled from rectangular hyperbolic functions determined for both sun and shade leaves and simulated from calculated light interception. Canopy leaf area, photosynthesis and PFDs within the canopy, obtained from measurements from vines grown in the orchard, were used to test the model. Close agreement occurred between the simulated and measured canopy leaf area development, and also between simulated and measured rates of photosynthesis. Total carbon acquisition over the growing season, estimated at 11 kg vine'1, compared closely with measured increments in vine biomass over the growing season. Results thus confirm the physiologically based model to be readily scalable to whole vines growing in orchard conditions.