EFFECT OF LEAF DISTRIBUTION IN THE CANOPY ON THE TOTAL DRY MATTER PRODUCTION IN GRAPEFRUIT TREES

Abstract

Abstract The effects on dry matter (DM) production of the relative exposure of leaves to irradiance were studied in ‘Marsh seedless’ grapefruit (Citrus paradisi Macf.) trees. Three different irradiance levels were selected: the sunny side (location L), the shaded side (location S), and inside the canopy (location D). DM production was determined by measuring the DM accumulation and volume increment of single fruits borne on girdled branches with a predetermined number of leaves. The DM accumulated at locations S and D represented ca. 75% and 16–18%, respectively, of the DM accumulated by fruits at location L. Volume increments of fruits at locations L, S, and D on girdled branches roughly corresponded to their DM accumulations. On the other hand, fruits on nongirdled branches reached a similar volume and DM content at all locations. Some of the DM utilized by the fruits borne at locations S and D on nongirdled branches must, therefore, have been produced by the leaves at location L. Calculations showed th...