ROOTSTOCK INFLUENCES SEASONAL DRY-MATTER AND CARBOHYDRATE CONTENT ANDPARTITIONING IN ABOVEGROUND COMPONENTS OF FLORDAPRINCE PEACH-TREES

Seasonal development of leaf area, leaf area index (LAI), dry matter, and carbohydrate content were measured from harvest 1992 to harvest 19 93 in above-ground components of 'Flordaprince' peach [Prunus persica (L,) Batsch] trees grafted on GF 677 (Prunus persica x Prunus amygdalu s) and MrS 2/5 (Prunus cerasifera free pollinated) rootstocks, which w idely differ in vigor, Whole trees were separated into fruit, leaves, shoots, 1-year-old wood and >1-year-old wood, Sampling dates were coin cident with key fruit and tree developmental stages: dormancy, fruit s et, pit hardening, and fruit harvest, Rootstock modified the vegetativ e vigor of the tree, the seasonal partitioning of dry matter, and star ch content in above-ground components, Leaf area, LAI, and total above -ground dry matter were twice as high in the most vigorous combination ('Flordaprince'/GF 677), which gave the highest yield. but had the lo west harvest index, Rootstock vigor did not affect soluble sugar conce ntration in any of the canopy components. Starch content was greatest during dormancy and in the oldest wood of GF 677 trees. During fruit d evelopment, starch content rapidly decreased in l-year old wood and pe rennial components; at pit hardening it was four times greater in MrS 2/5 than in GF 677 trees. The vegetative-to-fruit dry mass ratio by pi t hardening was 3:1 for MrS 2/5 and 9:1 for GF 677 trees, Competition with shoot growth apparently reduced fruit growth, particularly during Stage I and Stage II, as fruit size at harvest was significantly lowe r (17 %) in GF 677 than in MrS 2/5 trees.