Probing the inner sanctum of leaf phosphorus : measuring the fractions of leaf P

Background: In spite of the importance of phosphorus (P) to plant physiological function and growth, relatively few studies have quantified foliar P fractions in native plants in natural environments. Understanding how these P fractions vary with P availability, soil type and parent material should provide information on the importance of P storage versus its partitioning to cell ultrastructure versus active biochemical compounds. In the latest study evaluating foliar P fractions, McQuillan et al. (2020), this issue, have enlisted a novel technique to estimate these foliar P fractions for major groups of functional and structural compounds in native species of different taxa across sites west of the Great Dividing Range of Australia. Scope: Combined with recent studies of diverse tropical species, there is a conservative amount of lipid-membrane P and nucleic acid P across a threefold range of leaf P concentrations, from very low leaf P concentration to what could arguably be considered moderately low leaf P concentrations (0.3 to 1.0 mg g−1 leaf P concentration). Conclusions: The findings provide insight into how overall leaf P concentrations are partitioned, including that P investment in structural components of the leaf like membrane phospholipids is remarkably conservatively regulated. Further insights await a quantification of organelle-specific P fractions on well-preserved samples, so importance of the storage versus biochemical functions of orthophosphate can be elucidated. These insights will be important for incorporating functional components of P and P biogeochemistry into models of ecosystem function, for understanding how P may regulate global change responses.