EFFECT OF SOIL MATRIC POTENTIAL ON LEAF WATER POTENTIAL, DIFFUSIVE RESISTANCE, GROWTH AND DEVELOPMENT OF GMELINA-ARBOREA L SEEDLINGS

Gmelina arborea L. seedling growth and diurnal stomatal opening (as measured by stomatal resistance) were studied at soil matric potential 0, -0.1 and -0.72 × 10-5 Pa. Leaf area, leaf number, plant height and dry weights of the vegetative parts were significantly reduced as soil matric potential decreased from 0 to -0.72 × 10-5 Pa. The growth responses followed the same trend as net assimilation rate and relative growth rate. The highest moisture stress induced leaf senescence and leaf fall. Leaf water potential decreased from - 2 × 10-5 Pa to - 20 × 10-5 Pa with increasing soil moisture stress. Results indicate that the diurnal stomatal opening is controlled by photon flux density when this species is grown at soil matrio potential 0 Pa. However, with decreasing soil matrio potential (- 0.10 and -0.72 × 10-5 Pa) the internal plant water deficit appears to oontrol the stomatal opening. © 1979 Academia.