The synthetic auxin 3,5,6-TPA stimulates carbohydrate accumulation and growth in citrus fruit

The application of the synthetic auxin 3,5,6-TPA at the cell enlargement stage increased hexoses in developing fruit from foliated and fully defoliated plants of Satsuma mandarin, cv. 'Okitsu' (Citrus unshiu Marc.). Although the sucrose concentrations also increased, in general the differences were not statistically significant. The plant growth regulator reduced fruit abscission in defoliated trees while it stimulated fruit growth in the foliated ones. The carbohydrate accumulation induced by 3,5,6-TPA indicates that its stimulatory effect on fruit growth might operate via promotion of sink strength. The results also suggest the occurrence of pathways for induction of fruit abscission, linked to carbon availability, relatively independent of the stage of development.