Allometric relationships for vegetative growth flush in pruned stems of macadamia (Macadamia integrifolia): effects of carbohydrate source and season

• Published in: Crop and pasture science Vol. 68; no. 8; pp. 760 - 772
• Main Authors: Karimaei, S, Doley, D, Hanan, J
• Format: Journal Article
• Language: English
• Published: CSIRO Publishing 01.01.2017
• Subjects: L-system parameters; RESEARCH PAPERS; stem reserves
• ISSN: 1836-0947; 1836-5795
• DOI: 10.1071/CP17089

Hedging is used to control tree size in macadamia orchards, but the effects on subsequent shoot growth and floral initiation may impair fruit production. Four-year-old grafted macadamia (Macadamia integrifolia Maiden & Betche) trees were subjected to pruning of the most recent seasonal shoot in autumn and spring. Factorial combinations of treatments included girdling or not girdling near the base of the previous season’s (parent) shoot; removal of all except two, four or six leaves from the parent shoot; and defoliation or no defoliation of the shoot that appeared after pruning. Initial numbers and dimensions of flush-shoot internodes were similar for all branch treatments in autumn and for girdled branches in spring, and were smaller than half those for non-girdled stems in spring. Later flush-shoot growth depended on the number of leaves retained on the parent shoot, the presence or absence of a connection to the tree below the parent shoot, and on the season, declining with limiting growing degree-days in winter and accelerating with increasing growing degree-days in summer. In both seasons, reserves beyond the parent (previous season’s) shoot contributed the major source of carbohydrate for continuing flush-shoot growth, and particularly the growth of leaves. The combinations of seasonal conditions, shoot parameters before the commencement of flush-shoot growth, and flush-shoot morphology permit the inference of allometric relationships that can be applied to the quantitative modelling of vegetative shoot morphology and growth in macadamia.