Putting the P in Ptilotus: a phosphorus-accumulating herb native to Australia.


BACKGROUND AND AIMS Ptilotus polystachyus (green mulla mulla; ptilotus) is a short-lived perennial herb that occurs widely in Australia in arid and semi-arid regions with nutrient poor soils. As this species shows potential for domestication, its response to addition of phosphorus (P) and nitrogen (N) was compared to a variety of the domesticated exotic perennial pasture herb Cichorium intybus (chicory), 'Puna'. METHODS Pots were filled with 3 kg of an extremely nutrient-deficient sterilized field soil that contained 3 mg kg(-1) mineral N and 2 mg kg(-1) bicarbonate-extractable P. The growth and P and N accumulation of ptilotus and chicory in response to seven rates of readily available phosphorus (0-300 mg P pot(-1)) and nitrogen (N) (0-270 mg N pot(-1)) was examined. KEY RESULTS Ptilotus grew extremely well under low P conditions: shoot dry weights were 23, 6 and 1.7 times greater than for chicory at the three lowest levels of P addition, 0, 15 and 30 mg P pot(-1), respectively. Ptilotus could not downregulate P uptake. Concentrations of P in shoots approached 4% of dry weight and cryo-scanning electron microscopy and X-ray microanalysis showed 35-196 mM of P in cell vacuoles in a range of tissues from young leaves. Ptilotus had a remarkable tolerance of high P concentrations in shoots. While chicory exhibited symptoms of P toxicity at the highest rate of P addition (300 mg P pot(-1)), no symptoms were present for ptilotus. The two species responded in a similar manner to addition of N. CONCLUSIONS In comparison to chicory, ptilotus demonstrated an impressive ability to grow well under conditions of low and high P availability. Further study of the mechanisms of P uptake and tolerance in ptilotus is warranted.

DOI: 10.1093/aob/mcp021

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@article{Ryan2009PuttingTP, title={Putting the P in Ptilotus: a phosphorus-accumulating herb native to Australia.}, author={Megan H. Ryan and Stefanie Ehrenberg and Robb G. Bennett and Mark Tibbett}, journal={Annals of botany}, year={2009}, volume={103 6}, pages={901-11} }