Find in Library

Atmospheric nitrogen (N) deposition is coupled with organic nitrogen (ON) and inorganic nitrogen (IN); however, little is known about plant growth and the balance of elements in <i>Torreya grandis</i> growing under different ON/IN ratios. Here, we investigated the effects of ON/IN ratios (1/9, 3/7, 7/3, and 9/1) on leaf stoichiometry (LF), chlorophyll content, and chlorophyll fluorescence of <i>T. grandis</i>. We used ammonium nitrate as the IN source and an equal proportion of urea and glycine as the ON source. The different ON/IN ratios altered the stoichiometry and photochemical efficiency in <i>T. grandis</i>. Although the leaf P content increased significantly after treatment, leaf N and N:P maintained a certain homeostasis. <i>Torreya grandis</i> plants performed best at an ON/IN ratio of 3/7, with the highest values of chlorophyll-a, total chlorophyll, maximum photochemical efficiency, and photosynthetic performance index. Thus, both ON and IN types should be considered when assessing the responses of plant growth to increasing N deposition in the future. Our results also indicated that the leaf P concentration was positively correlated with Chl, Fv/Fm, and PIabs. This result further indicates the importance of the P element for plant growth against the background of nitrogen deposition. Overall, these results indicate that <i>T. grandis</i> might cope with changes in the environment by maintaining the homeostasis of element stoichiometry and the plasticity of PSII activity.