Photosynthesis and respiration were measured in the laboratory with an infrared CO2 analyser using attached leaves on Sultana vines growing either in the glasshouse or out of doors. At light saturation (2,500-3,000 f. c.) the photosynthetic rates approximated 8.5 and 10.5 mg CO/h/dm2 with light compensation points of 50 and 125 f. c. respectively. The optimum temperature for photosynthesis was between 25 and 30° C.Age effects were examined using shoots from well established field vines. Small but rapidly expanding terminal leaves showed no net photosynthesis but had a high rate of dark respiration and a CO2 compensation point above 300 ppm. With further expansion the leaves showed a steady increase in photosynthetic activity with a corresponding decline in dark respiration and CO2 compensation point. The rate of photosynthesis again declined with the onset of senescence
