Japanese plum (Prunus salicina L.) fruit growth: seasonal pattern of source/sink limitations

The seasonal pattern of Japanese plum (Prunus salicina L.) fruit growth and source/sink limitations to fruit growth were analyzed by a functional approach. The study was based on the comparison be tween unthinned and heavily-thinned trees of two plum cultivars, 'Black Amber' and 'Royal Diamond' (early- and late maturing cultivars, respectively). Individual fruit size, expressed as fruit dry weight, was significantly higher in trees with lower crop loads. The analysis of the relative growth rate patterns in dicated that plum fruit growth is limited by resource and genetic limitations (source and sink limitations, respectively). Both plum cultivars appeared to have a source-limited fruit growth period occurring in the stage I of the double-sigmoid fruit growth curve and a sink-limited stage occurring during the stage II. Although the fruits of the early-maturing cultivar accumulated less dry matter during their developmental time, compared to those of the late-maturing cultivar, they appear to have a higher potential net sink strength during their growth period.