DIURNAL-VARIATION OF STOMATAL-RESISTANCE TO WATER-VAPOR DIFFUSION IN IRRIGATED PEANUTS

The plant response of the peanut (Arachis hypogaea L.) crop submitted to two different levels of irrigation was evaluated with the objective of determining the diurnal variation of the stomatal resistence of th e BR-1 cultivar, and was related with the photon flux density of the p hotosynthetically active radiation. The experiment was conducted at th e Experimental Station belonging to the Companhia de Desenvolvimento d o Vale do S (a) over tilde o Francisco, situated in the municipality o f Rodelas, BA, Brazil. The soil is classified as fine sandy soil. The experiment was conducted during the period of August to December 1994. The planting took place on the 6th of August, 1994. The amounts of ir rigation applied were 300 mm and 700 mm, and the irrigations were appl ied at four-day intervals. The leaf stomatal resistences and the photo n flux density of the photosynthetically active radiation were measure d. Under non-stressed conditions, the peanut crop shows a hyperbolic r elation between the stomatal resistence and photon flux density. The w ater stressed plants present the phenomenon of stomatal closure around midday.