Maximum Fruit Growth Potential Following Resource Limitation During Peach Growth

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To achieve its maximum organ growth potential, an organ must grow at its potential relative growth rate (RGR) throughout development. When resource availability limits growth, the RGR is reduced below the potential RGR. This study examines whether, following a period of resource-limited growth, the RGR is able to increase to the potential RGR when sufficient resources are available. Fruit RGRs of a late maturing peach cultivar were examined following removal of most of the fruits (heavy thinning) from previously unthinned trees in Apr., May, and Jun. The fruit RGRs after imposition of the thinning treatments were higher than those on unthinned trees during source-limited periods of the growing season, suggesting that fruit RGR can increase in response to increased resource availability. In general, the RGRs of fruits of trees thinned in Apr., May, and Jun. did not exceed those of fruits on trees thinned at bloom, suggesting that heavy thinning at bloom provides a reasonable estimate of the potential RGR. There were times, however, when the effects of competition with vegetative sinks were apparent, suggesting that the RGR of fruits on trees that were heavily thinned at bloom may underestimate the potential RGR during these times. The absolute growth rates of fruits on thinned trees were greater than those on unthinned trees, but generally were not greater than those on trees that were thinned at bloom, suggesting that peach fruits are unable to recover potential growth lost during resource-limited growth periods.