Water transport in relation to expansion and contraction of leaves and fruits of Calamondin orangef

SummaryDiurnal fluctuations in fruit diameter and leaf thickness of Calamondin orange trees were measured and related to transpiration from leaves and to internal redistribution of water from fruits to leaves. While trees were well irrigated, leaf thickness began to decline daily around sunrise and to increase in mid-afternoon. Daily shrinkage and expansion of fruits began later than in leaves. The lag in response of leaf thickness changes to changes in vapour pressure deficit of the air was 1 or 2 hours, whereas the lag in response of fruit diameter was 3 or 4 hours. During imposed droughts, daily shrinkage of fruit and leaves continued until later in the day when the trees were well irrigated. Moreover, during a drought, expansion of the tissues at night occurred at a much slower rate than during periods of daily irrigation, or expansion did not occur at all. Movement of water from fruits to leaves on excised branches was indicated by the higher percentage moisture content of leaves on branches bearing fruits than of leaves on branches without fruits.