Chilling stress dramatically reduced Pn, while slightly reduced chlorophyll content in the leaves of the tomato seedlings (Fig. 2)compared to the control (p < 0.05). The Pn and chlorophyll content in CT plants were 74.25% and 92.87%, respectively, of these values in the control plants
When the N supply was 100% ammonium (an N-A ratio of 0:100),Pn and the chlorophyll content of leaves were reduced compared to other N-A ratios, in both temperatures (Fig. 2).
When the N supply was 100% ammonium (an N-A ratio of 0:100),Pn and the chlorophyll content of leaves were reduced compared toother N-A ratios, in both temperatures (Fig. 2). As with the growthparameters, there appeared to be an optimal N-A ratio for Pn, butthis ratio differed with respect to temperature. Net photosynthe-sis was greatest when the N-A ratio was 75:25 for the control,unchilled plants and 50:50 for plants grown at CTs. These optimalratios were the same for both photosynthesis and growth (Fig. 2,Table 2). The amount of chlorophyll was affected by the N-A ratioin the control plants, but not in the chilled plants