EFFECTS OF ANTITRANSPIRANT AND LEACHING ON MEDIUM SOLUTION OSMOTIC POTENTIAL, LEAF STOMATAL STATUS, TRANSPIRATION, ABSCISIC-ACID CONTENT AND PLANT-GROWTH IN EARLY-GIRL TOMATO PLANTS (LYCOPERSICON-ESCULENTUM)

Tomato plants (Lycopersicon esculentum Mill. cv. Early Girl) were grow n in a medium containing peat moss and perlite (60:40% by volume). The medium was drenched with 0 or 5% of antitranspirant GLK-8924. Half of the plants were hushed daily with 250 mi water (leaching) and the oth er half were subirrigated by capillarity. The osmotic potential of med ium solution was reduced significantly by 5% antitranspirant GLK-8924 treatment, then recovered gradually to the control level after 4 d wit h leaching and 10 d without leaching. Leaf stomatal conductance (g(s)) , transpiration rate (E) and plant growth were depressed by the antitr anspirant GLK-8924 application, and the depression was alleviated by l eaching. Neither antitranspirant GLK-8924 treatment nor leaching influ enced leaf abscisic acid (ABA) content. The effect of antitranspirant GLK-8924 on leaf gas exchange and plant growth was highly correlated w ith the reduction in the osmotic potential of medium solution but not with leaf ABA content. Younger leaves had higher g(s) and E but lower ABA content than older leaves in general.