Partitioning of photoassimilates in avocado (Persea americana Mill.) during flowering and fruit set.

To assess competition for photoassimilates among developing inflorescences, fruitlets and vegetative shoots in avocado (Persea americana Mill.), the distribution of recent photoassimilates was examined before and during flowering, fruit set, and the transition from sink to source of developing vegetative shoots. Mature leaves, located proximal to developing reproductive organs, and developing leaves, located distal to those organs, were exposed to a one-hour pulse of (14)CO(2). Translocation of radiolabeled assimilates was monitored over time and among organs. Overall distribution of assimilates was dependent on dry mass of tissues regardless of organ type. Flowers and fruitlets did not demonstrate greater sink strength than non-autotrophic leaves. Organs receiving assimilates were in phyllotactic alignment with source leaves. Photoassimilates were never limiting, although flower and fruitlet abscission occurred during and long after this competitive period. Carbohydrate availability was sufficient to support the growth of both developing fruitlets and leaves during early stages of reproductive development, and it did not limit fruitlet growth or stimulate fruitlet abscission.