Sex-specific nitrogen allocation tradeoffs in the leaves of Populus cathayana cuttings under salt and drought stress

Nitrogen (N) partitioning within a leaf affects leaf photosynthesis and adaptation to environmental fluctuations. However, how plant sex influences leaf N allocation and its tradeoffs in acclimation to drought, excess salt and their combination remains unknown. Here, leaf N allocation between the photosynthetic and non-photosynthetic apparatus and among the components of the photosynthesis in Populus cathayana Rehder females and males were investigated under drought, salt and their combination to clarify the underlying mechanism. We found that males with a lower leaf N allocation (N-L) into non-protein N (N-np), showed a greater leaf N allocation into photosynthetic apparatus, especially into the carboxylation component under all treatments, and a greater leaf N allocation into cell wall under drought and salt stress alone, consequently causing higher photosynthetic N use efficiency (PNUE) and tolerance to stresses. Conversely, females had a greater leaf N allocation into N-np under all treatments than males and a lower leaf photosynthetic N (NP) allocation. There was a tradeoff in leaf N allocation among photosynthetic apparatus (N-P/N-L), cell wall (N-CW/N-L) and N-np, which explained plant responses to drought, salt and their combination. Moreover, the leaf N allocation into the carboxylation component could explain the intersexual difference in responses to all treatments, while leaf cell wall N (N-CW) and N-np reflected intrasexual differences among treatments in both sexes. These findings indicate sex-specific strategies in coping with drought, salt and their combination that relate to leaf N allocation, which may contribute to sex-specific photosynthesis and niche segregation.

Automated summary

This study investigated nitrogen allocation in photosynthetic and non-photosynthetic apparatus of Populus cathayana Rehder females and males under drought, salt, and their combination. The results showed that males had lower leaf N allocation and higher photosynthetic N use efficiency, while females had higher allocation of N into non-protein N. Leaf N allocation was related to plant responses to different stress treatments, and there were intersexual and intrasexual differences in N allocation.