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ISHS Acta Horticulturae 1130: XXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposia on the Physiology of Perennial Fruit Crops and Production Systems and Mechanisation, Precision Horticulture and Robotics

Demystifying carbohydrate allocation to storage in fruit trees

Author:   T.M. DeJong
Keywords:   CHO reserves, carbon partitioning, starch storage, starch mobilization, xylem parenchyma
DOI:   10.17660/ActaHortic.2016.1130.49
In spite of the essential nature of long-term carbohydrate reserves for tree survival and productivity there has been confusion about how allocation of carbohydrates to storage reserves occurs in trees. The prevailing view has been that trees store carbohydrate reserves during times of “excess” photosynthate production (when current supply exceeds demands for growth and tissue metabolism) and deplete reserves when the potential rate of carbohydrate utilization exceeds the rate of current photosynthate production. However this concept has been challenged because storage reserves are so important for the survival of perennial plants and thus it is probably not correct to treat storage sinks as passive reservoirs. The lack of understanding or clear concepts regarding the dynamics of reserve storage and mobilization in perennial plants has been a major limitation in carbon budget models of tree growth and is a substantial unresolved issue facing pomologists, tree physiologists and ecologists. This paper reviews a logical basis for considering carbohydrate storage as an active sink and provides a method for quantifying and simulating annual carbohydrate storage and mobilization potential in temperate deciduous fruit trees. This view of carbohydrate storage leads to the hypothesis that the capacity for carbohydrate storage is largely a function of xylem and phloem anatomy and is created as trees grow. The amount of carbohydrate that is actually stored is a function of that capacity and the ability of storage sinks to actively compete for carbohydrates during and shortly after the growing season.

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