Differences in resistance to nitrogen and phosphorus deficiencies explain male-biased populations of poplar in nutrient-deficient habitats

Abstract

In most forest soils, the availability of nitrogen (N) and phosphorus (P) nutrients is low and unable to meet the requirement of tree growth. In the past decades, sex-based differences in poplar have been investigated in morphology and physiology. Proteomic techniques provide new insights into sex-specific differences at the molecular level. This review gives a comparative overview of the effects of N and P deficiencies on poplar physiological and proteomic characteristics. Male poplars are more efficient at photosynthesis and nutrient usage than females. Proteins related to carbohydrate metabolism, defence responses and transcription and translation processes are changed to adapt diversely in males and females. These results provide evidence that male poplar have better resistance to nutrient-limiting conditions than females, which may be reasonable for the male-biased sex ratio in nutrient-deficient habitats. Furthermore, this review also discusses the potential growth-defence trade-offs in male and female poplar coping with nutrient limitations.

Biological significance: In the past decades, the physiological and molecular responses of individual trees exposed to nutrient deficiency have been well studied. An important model woody plant, Populus, is dioecious and shows a male-biased sex ratio in nutrient-deficient habitats. Individually, different responses to nutrient limitation between the sexes determine the bias of population sex ratios. Proteomic techniques provide new insights into sex-based differences in the molecular mechanisms underlying nutrient deficiency. This review gives a comparative overview of the identification of nitrogen and phosphorus deficiency effects on physiological and proteomic characteristics. Male poplars are more resistant and have a smaller range of protein changes than females in response to N and P deficiency, which explains the observed male-biased sex ratios to a certain extent. Furthermore, this review also discusses the possible growth-defense trade-offs in male and female poplars coping with nutrient deficiency.

Keywords: Nutrient deficiency; Physiological process; Populus; Proteomics; Sexual differences.