STUDIES ON WETTING PHENOMENA ON PLANT LEAF SURFACES .1. EVALUATION OF WETTABILITY OF PLANT LEAF SURFACES

A leaf immersion method to evaluate leaf surface wettability was investigated. Retention figures of immersion solutions containing a dye (Direct Fast Scarlet 4BS) 1.0% and surfactant(s) 0.2% on leaf surfaces were classified into six types (A-E and O) and the specific retentions (Up-2) on leaf surfaces were obtained at immersion lengths of more than 10 cm for Gramineae and 5 cm for soybean, cowpea and others with a solution making a continuous thin film (A-I retention). Up-2 and whole-leaf retentions were measured for 23 crops from eight families. The former fell in a narrow range of ca. 0.6-1.1 mu-l/cm2 for all the leaves but the latter was divided into two groups; almost the same retention (Cucurbitaceae, Brassicaceae and Malvaceae) and fairly varied retention (Gramineae, Legminosae and Solanaceae). It was possible to evaluate wettability on specific retention figures with the leaf immersion method we have developed.