Sex-specific carbon and nitrogen partitioning under N deposition in Populus cathayana

Abstract

Key message Females of Populus cathayana allocated increased N to soluble proteins, while males keep N allocation pattern unchanged under N enrichment. Abstract In our study, Populus cathayana as a model species is employed to detect the sex-specific responses in growth, photosynthetic nitrogen (N) use efficiency (PNUE), carbon (C) and N partitioning when exposed to 0, 7.5 and 15 g N m -2 year -1 on the basis of local N deposition level. Our results showed that females had higher responses in photosynthesis and growth than males when exposed to N deposition, and also exhibited higher PNUE than males when exposed to high level of N deposition, suggesting that plasticity in the females may enhance the capacity of young seedlings to acquire resources. Moreover, we found that females mainly allocated increased N to soluble proteins and detergent-soluble proteins, but not to cell-wall proteins, while males maintained original partitioning pattern of N and also accumulated excessive N in the form of free amino acids. Females also allocated more fraction of leaf N to carboxylation (P C ), bioenergetics (P B ), and then more fraction of leaf N to all components of photosynthetic machinery (P T ) than males under high level of N deposition. Such sex-specific N allocation strategy may correlate with sex-related PNUE. These results indicated that there is a higher critical N demand in females, and females could use N nutrient more efficiently than males under high N deposition. We also found that higher shift from starch to soluble sugars, such as sucrose, occurred in females than in males under N enrichment. By contrast, excessive accumulation of starch and non-structural carbohydrate in females relative to males was observed under control conditions, which might inhibit female photosynthesis rate. Accordingly, we suggested that the different leaf C and N partitioning patterns could explain the sex-specific responses in growth. Therefore, females may obtain advantageous position in the process of intraspecific competition when exposed to high level of N deposition because they have higher light capture (total leaf area) ability and utilization efficiency (PNUE) than the males that confer the ability for fast growth and thus are likely to be more responsive to N enrichment. Our results suggested that it could be important to look at the stronger growth response of the females over the males under N enrichment at both the leaf and the plant scale.

Males and females of Juniperus communis L. and Taxus baccata L. show different seasonal patterns of nitrogen and carbon content in needles

“…Thereafter, N began to increase after flowering in the male, but in females it carried on decreasing, leading to the greatest differences between sexes from April to August. This accords with previous studies on Rubus chamaemorus and Populus cathayana where N concentration was frequently higher in male than in female plants (Agren et al 1999;Chen et al 2014), and partly with observations on Honkenya peploides where the N concentration of females decreased from April to August, while in males a decrease was only found from April to June (Vilas and Retuerto 2016). The data in our study, however, demonstrate these changes for the first time in an evergreen dioecious woody species, and that the greatest differences in N concentration are during intensive plant growth.…”

“…Carbon demand is very high during the formation and maturation of reproductive structures (McDowell et al 2000) and yet no difference was found in the C concentration of the leaves between the sexes. A similar result was observed, however, in Populus cathayana (Chen et al 2014) suggesting that this is a more general relationship in dioecious plants. Greater reproductive effort in females is probably compensated for by a higher rate of gas exchange and photosynthesis.…”

“…At fruit maturation (September) the concentration of N was significantly higher in males than females but only in one of two sites investigated (Cipollini and Stiles 1991). Lower N concentration was also demonstrated in females of Populus cathayana (Chen et al 2014) and Acer negundo (Dawson and Ehleringer 1993). In other studies where the level of N was examined once in the season, no differences were usually found between the sexes (Agren et al 1999;Jiang et al 2016).…”

“…However, so far, no significant differences between C concentration between males and females have been found (Chen et al 2014;Jiang et al 2016). For example, no seasonal difference was found in non-structural carbohydrate concentration between males and females in Juniperus thurifera (DeSoto et al 2016).…”

“…Females usually support higher reproductive effort than males (e.g. Obeso 2002; Montesinos et al 2006) and consequently allocate more resources to reproduction resulting in slower radial growth after reaching sexual maturity (Obeso 2002;Banuelos and Obeso 2004;Montesinos et al 2006;Chen et al 2014). Females are also often more demanding of habitat requirements (Obeso 2002;Chen et al 2014) which may be a reason behind the spatial segregation of the sexes in some species (Bierzychudek and Eckhart 1988;Dawson and Ehleringer 1993;Matsushita et al 2016).…”