Diurnal Changes in Diameters of Fruits and Tree Stems of Montmorency Cherry

Abstract

SummaryDiurnal expansion and contraction of fruits and tree stems of Montmorency cherry (Prunus cerasus L.) were studied during various stages of fruit development. Experiments were performed under conditions of frequent irrigation as well as during soil-drying cycles. Fruits in a mid stage of development often shrank during the morning and early afternoon and expanded, beginning in late afternoon and continuing into the night. Fruits in mid stages of development usually shrank more than stems. The time of beginning, amount, and duration of shrinkage varied with the stage of fruit development, soil moisture availability, weather, and degree of internal water stress in the tree. When soil moisture contents were high the amount, time, and ending of daily shrinkage were correlated with conditions affecting transpiration. During early development (stage I) fruits usually increased in diameter in spurts and did not shrink appreciably during the day, except under severe internal water stress. As fruits approached maturity (stage III) they showed a strong tendency for water uptake and limited water loss. In nearly mature fruits afternoon expansion tended to predominate even when the soil was dry. Maturing fruits could be made to shrink appreciably, however, by high internal water deficits.