INFLUENCE OF PHOSPHORUS DEFICIENCY ON POSTIRRADIATION BURST OF CO2 FROM BEAN (PHASEOLUS-VULGARIS L) LEAVES

The effect of phosphorus nutrition on the post-irradiation burst of CO 2 (PIB) in primary leaves of 14-d-old bean (Phaseolus vulgaris L. cv. Golden Saxa) seedlings was studied by infrared gas analysis in a close d gas exchange system. PIE parameters (duration, rate and volume) were measured under CO2 concentration near to CO2 compensation concentrati on, irradiance of 200 or 500 mu mol m(-2) s(-1), oxygen concentration 21 or 50%, and leaf temperature of 15, 20 or 25 degrees C. The decreas e in the leaf phosphorus content, 5-fold of the total phosphorus and 1 0-fold of inorganic orthophosphate, caused only reduction about 20% in the net photosynthetic rate and 10% in the dark respiration rate. How ever, phosphorus deficiency at the 21% O-2 concentration in the atmosp here resulted in a marked decrease in PIB. This effect was eliminated by the rise in O-2 concentration up to 50%.