Contrasting phosphorus sensitivity of two Australian native monocots adapted to different habitats

Abstract

Contrasting nutrient-acquisition strategies would explain why species differ in their distribution in relation to soil phosphorus (P) availability, promoting diversity. However, what drives the differential distribution of plant species with the same P-acquisition strategy remains poorly understood. We selected two Haemodoraceae species, Anigozanthos flavidus and Macropidia fuliginosa, to investigate physiological responses in non-mycorrhizal monocots adapted to different edaphic habitats that vary in P availability. Plants were grown in nutrient solution in large tanks at a range of P concentrations (0, 0.1, 1, 10 µM P). After seven months, we measured growth, photosynthetic rate, net P-uptake capacity, and leaf [P]. Fresh weights of A. flavidus plants were highest at 1 µM P and lowest at 0 µM P. Fresh weights of M. fuliginosa plants were lowest at 10 µM P compared with those at other P levels. Rates of P uptake by A. flavidus showed a steady decline with increasing P level during growth from 0 to 1 µM P, and then a sharp decline from 1 to 10 µM P. Rates of P uptake in M. fuliginosa did not differ among growth P levels, except between 0 and 1 µM P. Both species showed a drastic increase in the concentration of both total P and inorganic P at 10 µM P. The results support our hypothesis that A. flavidus is efficient in down-regulating its P-uptake capacity, while M. fuliginosa is not. Thus, partly explaining the narrower and wider distribution of these species.