Covariations and tradeoffs of phosphorus (P) acquisition strategies in dioecious Populus euphratica as affected by soil water availability

1. Dioecious species may be particularly vulnerable to climate change
because they often exhibit skewed sex ratios that are reinforced by the
physiological and biological specialization of each sex to specific
microhabitats. Yet, it is unclear how differences in functional traits
between female and male plants lead to sex-specific responses to drought
and whether these responses are associated with phosphorus (P) acquisition
diverge or converge. 2. Here, we measured the morphological and
physiological traits of roots, and the functional microorganisms related
to P acquisition in Populus euphratica females and males
in the rhizosphere under different water availability. 3. The specific
root length of females was greater than that of males, regardless of soil
water availability. Therefore, the P concentration of females was
significantly higher than that of males under well-watered conditions. In
contrast, the physiological adjustment to drought showed distinct sexual
patterns: males significantly increased the foliar manganese concentration
and maintained higher acid phosphatase activities in the rhizosphere.
Moreover, the arbuscular mycorrhizal hyphal biomass was reduced less in
males than in females under water deficiency. Soil water shortage also
decreased the α diversity of phosphate solubilizing bacteria (PSB) and
changed the co-occurrence network in the rhizosphere of females, but it
had little effect on males. Therefore, the favorable physiological
processes and effective maintenance of functional microbial homeostasis in
the rhizosphere were the reasons that enabled males to reduce P loss in
leaves under water deficiency. 4. Our study indicated that,
within P. euphratica populations, covariations
and tradeoffs simultaneously occurred among the three groups (root
morphology, physiology, and functional microorganisms) of functional
traits evaluated. More generally, the assessment of variations in
sex-specific P acquisition strategies may help to understand the causes of
sex ratio bias and how P. euphratica males and females
mitigate resource shortage.