The role of carbohydrate reserves in evergreen tree development, with particular reference to macadamia

Abstract

We take three approaches to more clearly define the role of carbohydrate (CHO) reserves in the development of evergreen trees. First, we examine the lychee and macadamia literature to develop a whole tree carbon budget to show that current photosynthatemakes a greater contribution to the carbon for new growth than CHO reserves. Second, we show that the presence of leaves is sufficient for the production of a functional new shoots on small, girdled branches with few CHO reserves. Third, we use a shade experiment to show that short-term suppression of whole-tree photosynthesis can severely affect new shoot development. Subsequent decapitation of all branches on both the shaded and control trees resulted in faster bud release in the shaded trees, notwithstanding lower CHO reserves. Overall we argue that the main role of CHO reserves is to buffer the pool of current photosynthate. Although such buffering can be quite strong during periods of high carbon demand, even then CHO reserves are a secondary source of carbon.