Matured leaves of Hevea brasiliensis were used to examine the relationship between excess excitation energy and senescence of green leaves experiencing stress. From simultaneous measurements of chlorophyll fluorescence and gas exchange by leaves, the rate of photosynthetic carbon assimilation (A) and the rate of in vivo electron transport across photosystem II (J) were determined. Rate of photosynthetic elctron diversion away from the carbon reduction (J*), presumably for oxygen reduction leading to the production of reactive species of oxygen(ROS) and free radicals (FR) were estimated. Both A and J increased and J* decreased when intact leaves were exposed to elevated concentration of CO2 and all these parameters increased at high light intensity. But A and J decreased and J* increased when the leaves were excised. In the excised leaf A was more and J* was less at elevated CO2 concentration. An increase in J* in plants with injured roots was observed which led to an inhibition in the quantum yield of PSII activity and was related to ageing as indicated by a loss of chlorophyll content of the leaf. Green leaves experiencing stress, increased diversion of electrons away from carbon to oxygen under conditions of high light intensity hastens leaf senescence, possibly through the production of destructive ROS and FR. Significance of the light environment inside a hevea canopy vis-a-vis leaf aging is discussed in the context of unfavourable environmental conditions.