Reproductive-vegetative shoot growth interactions and relationship to non-structural carbohydrates in immature ponkan mandarin (Citrus reticulata Blanco)

Abstract

SummaryThe relationship of leaf carbohydrates to vegetative and reproductive growth during an annual growth cycle in young trees of ponkan (Citrus reticulata Blanco) was monitored over two consecutive seasons. Fruiting, return bloom and fruit set was greater and more uniform in high fruit-load trees. These trees developed less vegetative growth and produced fruit with higher total soluble solids and skin colour than in trees with lower fruit loads. At anthesis, high fruit-set trees (20%) had higher starch and/or sucrose content in the leaves. Conversely, low fruit-load trees set less fruit (8%) despite having heavy return bloom and showed greater variation in fruit numbers per tree. They developed more vegetative shoot growth and had lower sucrose and/or starch content in the leaves at anthesis despite bearing fewer fruits per tree. Fruiting efficiency (fruits per cubic meter of canopy) was highest in the high fruit-load trees and lowest in the low-load and defruited trees.