THE SEASONAL CYCLE OF LEAF, SHOOT AND BUD DEVELOPMENT IN KIWIFRUIT

This study describes the cycle of leaf growth and shoot growth, and of shoot bud development on those shoots, from inception in early spring through to elongation the following spring. To describe the key devel opmental events, measurements of shoot length, leaf number, leaf area and counts of flower number were made on shoots in the held. Microscop ic examination of shoot buds was carried out periodically in the labor atory. Buds were dissected, and the numbers of leaves, axillary primor dia, and basal buds within each bud assessed. The field study was carr ied out using four populations of shoots, at two sites and in two seas ons to verify the observed trends. Spring-breaking shoots grew from mi d-September (bud break) to mid-summer, summer-breaking shoots grew fro m early January (bud break) to early April. Summer-breaking shoots wer e longer and had larger leaves than spring-breaking shoots. Shoot buds began to develop as the shoot began to elongate, they contained sever al leaf initials when the shoot was at bud break. By mid-January shoot buds on spring-breaking shoots contained 20-22 leaves. Buds reached a maximum size at approximately the same time as the subtending leaves ceased growth. Axillary primordia appeared in buds on spring-breaking shoots in mid-November. Buds contained a maximum of 3-4 basal buds and 9-12 axillary primordia at the sites of next year's flowers. Shoot bu ds at nodes 7-12 were examined in detail as these are some of the earl iest buds to develop and also some of the largest buds. These buds con tinued to grow for several months after their subtending leaves reach full-size. Maximum numbers of leaves and axillary structures were achi eved within the buds at similar times. Buds at nodes 7-12 on shoots in all populations were morphologically similar, with terminal buds tend ing to be slightly smaller than other buds. In the following spring, b etween 97 and 99% of buds elongated to become floral shoots, with betw een three and five flowers per