Sexually different physiological responses of Populus cathayana to nitrogen and phosphorus deficiencies

Previous studies have shown that there are significant sexual differences in the morphological and physiological responses of Populus cathayana Rehder under stressful conditions. However, little is known about sex-specific differences in responses to nutrient deficiencies. In this study, the effects of nitrogen (N) and phosphorus (P) deficiencies on the morphological, physiological and chloroplast ultrastructural traits of P. cathayana males and females were investigated. The results showed that N and P deficiencies significantly decreased plant growth, foliar N and P contents, chlorophyll content, photosynthesis, and instantaneous photosynthetic N- and P-use efficiencies (PNUE and PPUE) in both sexes. Males had higher photosynthesis, higher PNUE and PPUE rates, and a lower accumulation of plastoglobules in chloroplasts than did females when exposed to N- and P-deficiency conditions. Nitrogen-deficient males had higher glutamate dehydrogenase and peroxidase activities, and a more intact chloroplast ultrastructure, but less starch accumulation than did N-deficient females. Phosphorus-deficient males had higher nitrate reductase, glutamine synthetase and acid phosphatase activities, but a lower foliar N : P ratio and less PSII damage than did P-deficient females. These results suggest that N and P deficiencies cause greater negative effects on females than on males, and that the different sexes of P. cathayana may employ different strategies to cope with N and P deficiencies.