INFLUENCE OF NITROGEN SUPPLY AND TEMPERATURE ON STABLE CARBON-ISOTOPERATIOS IN PLANTS OF DIFFERENT PHOTOSYNTHETIC PATHWAYS (C(3), C(4), CAM)

One representative species of each of the three photosynthetic pathway s (C3, C4, CAM) were cultivated in growth chambers with high and low n itrogen nutrition level respectively once at 20-degrees-C day/13-degre es-C night temperature, once at 30-degrees-C day/13-degrees-C night. L eaf conductances and deltaC-13 values of the leaves of each plant were determined. At 20-degrees-C day temperature the C3 species showed hig her leaf conductance with low nitrogen nutrition level than with high nitrogen level, which is also reflected in a more negative deltaC-13 v alue, whereas both C4 and CAM plants did not respond in this manner to nitrogen supply. An increase of day temperature to 30-degrees-C dimin ished the significant response of the C3 plant, while the response of C4 and CAM representatives to nitrogen nutrition did not change marked ly.