Levy, Y., Agricultural Research Organization, Gilat Regional Experiment Station, Mobile Post, Negev, Israel

Conductance, transpirational flux and xylem pressure potential were measured in leaves of well-watered 5-year-old lemon trees (Citrus limon (L.) Burm. f.) subjected to different levels of evaporative demand. Increased leaf-to-air absolute humidity difference generally decreased stomatal conductance and increased xylem pressure potential, with a good correlation between the last two parameters; but this trend was reversed on days with very high evaporative demand, when stomata opened in spite of the low humidity. © 1980 Annals of Botany Company.