High Altitude Plant Physiology Research Centre, Garhwal University, Srinagar-246174, U.P., India.
Studies on diurnal variations in leaf temperature, water vapour transfer and energy balance per unit leaf area in the seedlings of Grewia oppositifolia revealed that it is slightly undertemperature plant, in which the resistance to water vapour tranfer (diffusion and stomatal resistance) decreased and the rate of transpiration and the energy emitted through transpiration increased with the leaf age. The total energy absorbed and that emitted through surface radiation and convection were not influenced significantly by the leaf age. The correlation coefficient indicated that while transpiration rate and stomatal resistance is influenced more by the leaf age rather than by dimensions, the total diffusion resistance to the water vapour transfer is influenced more by the leaf dimensions. The low leaf temperature, convectional energy and high radiation probably leads to slower flow of water vapour from leaf to its surrounding which would help in cooling down atmosphere around the plant.
