Requirements for obtaining maximum indices of photosynthesis and transpiration in attached leaves of willow plants grown in short-rotation forest

• Published in: Russian journal of plant physiology 2007-05, Vol.54 (3), p.309-313
• Main Authors: Kaipiainen, E. L, Pelkonen, P
• Format: Article
• Language: English
• Subjects: light; net photosynthesis; relative air humidity; Salix sp; temperature; transpiration
• ISSN: 1021-4437; 1608-3407
• DOI: 10.1134/S102144370703003X

The results of multiyear studies of gas exchange in intact attached leaves of several willow species (Salix sp.) were analyzed. Measurements were performed with a portable Li-6400 infrared gas analyzer both on plants in their natural environment and on rooted cuttings grown in a greenhouse. Individual attached leaves were placed into the leaf chamber where climatic conditions were either similar to or different from those outside the chamber. The maximal rates of net photosynthesis (P n) and transpiration (E) were only observed with the provision that the environmental variables inside and outside the chamber were identical. On rainy or cloudy days, the P n and E values observed under optimum conditions inside the leaf chamber were lower than their potential maxima by 12-18% and 35-45%, respectively. Deviation of temperature in the chamber by 5-7°C from the external level and fluctuations of ambient temperature affected P n but not E rates of tested leaves. Variations in relative air humidity in the chamber directly influenced E but had no effect on P n of attached leaves. It was shown that the maximum rates of gas exchange in the attached willow leaf could be only attained by providing optimum conditions for the whole plant.