Sink priority on 'Hayward' kiwifruit vines

Abstract

An experimental system based on girdled shoots was used to assess how vegetative competition alters the growth of 'Hayward' kiwifruit. Each shoot was pruned to length so that it contained four source leaves and a sink consisting of either a single fruit, a vegetative regrowth, or one fruit and a vegetative regrowth. Vegetative competition had the greatest effect on fruit growth when it occurred about five weeks after flowering, when fruit growth is maximal. When a single fruit was in competition with a defoliated vegetative shoot, fruit size at harvest was reduced by 50%, whereas competition 20 days later reduced the fruit size by only 28%. Our results show that vegetative growth has a higher sink priority than fruit for both fresh weight and dry weight (DW) for the first 120 days after flowering, the time when most fruit growth occurs. Furthermore, during this period vegetative growth had a higher sink strength for DW than fruit. As a consequence of sink priority, when there is competition for limited resources, shoot growth continues at the expense of fruit growth. © 2012 The Royal Society of New Zealand.