Leaf Conductance in Relation to Assimilation in Eucalyptus pauciflora Sieb. ex Spreng: Influence of Irradiance and Partial Pressure of Carbon Dioxide

Abstract

Rates of assimilation and transpiration in Eucalyptus pauciflora Sieb. ex Spreng were measured at various ambient partial pressures of CO(2) and various irradiances and were used to estimate leaf conductance and intercellular partial pressure of CO(2). The responses of leaf conductance and rate of assimilation to change in intercellular partial pressure of CO(2) were expressed in terms of feedback. They are small in the sense that their combined effect was to reduce disturbances in intercellular partial pressure of CO(2) by 30% only. The magnitude of the feedback had no influence on the system as affected by irradiance, because the direct responses of conductance and rate of assimilation to changes in irradiance in the range 0.25 to 2 millieinsteins per meter per second were such that intercellular partial pressure was maintained almost constant.