Physiological responses of kiwifruit vines (Actinidia chinensis Planch. var. chinensis) to trunk girdling and root pruning

Abstract

Hydraulic conductance and photosynthesis were measured in kiwifruit (Actinidia sp.) vines to observe responses to the horticultural practices of trunk girdling and root pruning. Little is understood regarding the physiological effects of these practices in kiwifruit. Combined reductions in hydraulic conductance and photosynthesis were expected following root pruning. The primary response to trunk girdling was expected to be photosynthetic. Measurements of transpiration and xylem pressure potentials (Ψ) were used to calculate hydraulic conductance (K). Stomatal conductance (g s) and photosynthesis (A) were measured periodically. Neither treatment affected fruit growth. The response to root pruning was primarily hydraulic with significant reductions in midday Ψ indicating reduced K; reductions in A and g s were small. Girdling resulted in significant reductions in g s and A, with little effect on Ψ or K. Reduced A following girdling was considered to be a consequence of stomatal and biochemical limitation, with biochemical down-regulation following reduced carbohydrate demand.