Gibberellins and Abscisic Acid Promote Carbon Allocation in Roots and Berries of Grapevines

Carbon allocation within grapevines may affect berry growth and development. The plant hormones gibberellins (GAs) and abscisic acid (ABA) control various processes across the plant life and both have been involved in assimilate production and transport in different species. Hence, this work examined the distribution of sugars (sucrose, fructose, and glucose) and starch in grapevines at veraison after foliar applications of GA 3 , ABA, and an inhibitor of GA biosynthesis, paclobutrazol (PBZ). The results demonstrated that GA 3 increased total grapevine mass, with carbon allocated to the whole grapevine (as structural and soluble carbohydrates). Both GA 3 and ABA increased monosaccharide (glucose and fructose) levels in berries (up to tenfold) and roots (up to threefold). However, GA 3 increased the net carbon fixation whereas ABA did not. PBZ diminished most growth parameters except grapevine mass, and allocated more carbohydrates to roots (up to threefold more sucrose and starch). Such results indicate that GAs promote net carbon fixation and transport, whereas ABA as a stress signal only enhances sugar transport; notwithstanding the two hormones promoted carbon allocation toward roots and berries.