Submitted to: Annual Cumberland Shenandoah Fruit Workers Conference
Publication Type: Proceedings
Publication Acceptance Date: January 9, 1995
Publication Date: N/A
Interpretive Summary: Leaves carry out photosynthesis, the process whereby the energy of sunlight is converted to sugar and starch for food storage in the plant. Mobilization of these stored reserves occurs at different stages of the plant's development, for example during flower production or in the developing seed or fruit. In peaches, there is generally a positive relation between the growth of the vegetative parts of the tree (i.e., leaves and branches) and subsequent flower development; however, if vegetative growth is excessive, fewer flowers are produced. In addition, it is not uncommon for the tree to produce new leaves at a steady rate for several months in the mid-spring to early summer, followed by a period in which the branches cease producing new leaves. Usually new leaf production resumes by mid to late summer. It is not clear how this period of vegetative "inactivity" influences flower production and subsequent fruit development. Nor has the influence of flowering and fruiting on photosynthesis been examined at the level of the individual leaf. The current study is an investigation of leaf growth measured by the increase in leaf length during the first phase of the growing season and during a year in which no flowers were produced by the trees. Results from this study will be compared to subsequent examination of leaf growth when the trees are in full flower to determine if there is a correlation in the next year's fruit set and development. Information from these studies will suggest strategies for controlling vegetative growth to maximize fruit production and quality.
Technical Abstract: Leaf expansion in peach (Prunus persica cv Loring) was measured by the increase in blade length as a function of leaf position and time after vegetative bud break. Measurements were made on a total of 20 apical shoots (2 trees) in the late spring and early summer of 1994, a season in which the trees were essentially vegetative with less than one flower observed per tree. Although leaf development was asynchronous, general trends in expansion of the shoot could be detected. On the average, leaves 1 through 5 (numbered acropetally) ceased expansion around 30 days after bud break, whereas leaves 6 through 9 continued expanding up to 52 days after bud break. For the most part, leaves 13 through 22 were still expanding at the last measurement taken. The basal three leaves of each shoot were noticeably smaller at full expansion than leaves 4 through 12 and most showed visible signs of senescence by 30 days after bud break. By 63 days after bud break, most of the shoot tips (12 out of 20) had ceased producing new leaves. Information from this study will be used for comparison with leaf expansion under flowering conditions.