Abstract
To estimate leaf water potential by measuring leaf greenness of Melon(Cucumis melo L.), leaf water potential(ψleaf)and leaf greenness value(〓D)were measured successively in a day. Both ψleaf and 〓D oscillated diurnally ; ψlear decreased during day and increased during night, and 〓D increased during day and decreased during night. Their changes were 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 formation in young leaves during daytime. We consider it highly feasible to use 〓D as an indicator to know ψlear 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.
