SHOOT TYPE AND LIGHT EXPOSURE INFLUENCE CARBON PARTITIONING IN PEACH CV ELEGANT LADY

Carbon partitioning and translocation in one year old fruiting limbs o f 'Elegant Lady' peach (Prunus persica L. (Batsch)) was studied, as af fected by source (leaves on actively growing extension shoots (EXT), l eaves on lateral shoots at nodes carrying (F) or not carrying (NF) fru it), and by light regime (full sun or 5 d 70% shade conditioning), fiv e times during the season (2, 4, 7, 11, 17 weeks after full bloom (WAF B)). Growing shoot apices were the strongest sinks early in the season (2 WAFB), with the EXT apices capable of attracting more carbon (C) a nd over longer distances, than the NF or F ones. The major source of n ewly synthesized carbohydrates for fruit growth 2 WAFB was the F later al shoot, i.e. the most important C contributor for fruit growth well into stage II (11 WAFB in this study). EXT shoots began contributing t o fruit growth before the NF shoots: 4 WAFB on, they exported to the f ruits in amounts similar to the F shoots. This contribution was even l arger 17 WAFB, when the F shoots retained more C than the other two sh oot types. The NF shoots exported to growing apices 2 WAFB, but export decreased 4, 7, and 11 WAFB, compared with the other treatments. NF s hoots contributed to fruit growth in the same amounts as the EXT shoot s 17 WAFB, and more than the F shoots. Shade did not consistently affe ct patterns of carbon partitioning within limb components, except for the F treatment, where it diminished C export to the fruit in the firs t four treatment dates. Partitioning within fruit components (mesocarp , endocarp and seed) followed the fruit growth curve, with more C allo cated to endocarp tissues at 11 WAFB (stage II). Results are in agreem ent with, and substantiate, earlier findings concerning the effects of fruit position on the limb, and competition for carbon with active ve getative sinks on fruit development.