THE INFLUENCE OF PLANT WATER DEFICIT ON DISTRIBUTION OF C-14-LABELED ASSIMILATES IN CACAO SEEDLINGS

The relationship between plant water status and distribution of 14C-labelled assimilates in cacao (Theobroma cacao L.) was evaluated after 14CO2 pulse labelling leaves of seedlings subjected to varying levels of water deficiency. The proportion of 14C exported by source leaves was strongly affected by seedling water status. An increasing proportion of labelled assimilates remained in source leaves at both 24-h and 72-h harvests as water stress intensity increased. Water stress reduced the distribution of exported label to leaves and to the expanding flush in particular but increased the proportion of label in stems and roots. The results suggest that current photoassimilates may be temporarily stored in source leaves and stems of cacao seedlings during periods of plant water deficit. The stress-induced changes in partitioning of labelled carbon were in concordance with changes in shoot to root biomass ratios, which was likely due to greater reduction in growth of above-ground organs to that of roots. © 1990 Annals of Botany Company.