PHOTOSYNTHETIC CHARACTERISTICS OF ACACIA-AURICULIFORMIS

The basic photosynthetic gas exchange characteristics such as response of net photosynthetic rate (P(N)), transpiration rate (E) and stomata l conductance (g(s)) to temperature, irradiance and vapour pressure de ficit (vpd) were investigated m Acacia auriculiformis. Maximum P(N), 1 2 mumol m-2 s-1, was observed at 30-degrees-C, PPFD 1000 mumol(photon) m-2 s-1 and vpd between air and leaf of 12 mmol(H2O) mol-1(air). The effect of irradiance showed that at high temperature A. auriculiformis may undergo photoinhibition whereas at low temperature overall photos ynthetic efficiency was low. The response of P(N) to temperature indic ates that there was a relatively broad temperature optimum of 25-35-de grees-C. The study also indicated that A. auriculiformis has the abili ty to adjust its photosynthetic response to its growth temperature and hence optimum temperature has very little importance in determining t he performance of Acacia. The response of P(N) and g(s) to changing te mperature and vpd indicates that a stomatal response to vpd provides a n effective mechanism for maximizing water use efficiency at changing leaf temperature.