Estimation of diurnal change in leaf water potential of melon through leafgreenness

To estimate leaf water potential by measuring leaf greenness of Melon (Cucu mis melo L.), leaf water potential (psi (leaf)) and leaf greenness value(De ltaD) were measured successively in a day. Both psi leaf and DeltaD oscilla ted diurnally; psi (leaf) decreased during day and increased during night, and DeltaD increased during day and decreased during night. Their changes w ere highly correlated negatively. They were more closely correlated during night than during day and more closely in old leaves than in young ones. A factor causing the discrepancy was considered to be new chlorophyll formati on in young leaves during daytime. We consider it highly feasible to use De ltaD as an indicator to know psi (leaf) after substructing other background effects, such as varietal characteristics, nitrogen fertilizer level, and amount of solar radiation, and to utilize it for precise irrigation control .