Carbon Partitioning as Affected by Shoot Type and Light Exposure in Peach

Abstract

Carbon partitioning and translocation in 1-year-old fruiting limbs of the peach cultivar Elegant Lady was studied, as affected by source [leaves on actively growing extension shoots (EXT), or on lateral shoots emerging from nodes with (F) or without (NF) fruit], five times during the season [2, 4, 7, 11, 17 weeks after full bloom (WAFB)]. Growing shoot apices were the strongest sinks early in the season (2 WAFB), with the EXT apices capable of attracting more C, and over longer distances, than the NF or F ones. The major source of newly synthesized carbohydrates for fruit growth 2 WAFB was the F lateral shoot; i.e., the most-important C contributor for fruit growth well into stage II (11 WAFB in this study). EXT shoots began contributing to fruit growth before the NF ones: 4 WAFB on, they exported to the fruit in amounts similar to the F shoots. This contribution was even larger 17 WAFB, when the F shoots retained more C than the other two shoot types. The NF shoots exported to the growing apices 2 WAFB, but this export decreased 4, 7, and 11 WAFB, compared to the other treatments. Seventeen WAFB, they contributed to fruit growth in the same amounts as the EXT shoots, and more than the F ones. Shade did not consistently affect patterns of carbon partitioning within limb components, except for the F treatment, where it diminished C export to the fruit in the first four treatment dates. Partitioning within fruit components (mesocarp, endocarp, and seed) followed the fruit growth curve, with more C allocated to endocarp tissues at 11 WAFB (stage II).