title: Mechanisms for tolerance of very high tissue phosphorus concentrations in Ptilotus polystachyus.
abstract: Study of plants with unusual phosphorus (P) physiology may assist development of more P-efficient crops. Ptilotus polystachyus grows well at high P supply, when shoot P concentrations ([P]) may exceed 40 mg P g(-1) dry matter (DM). We explored the P physiology of P. polystachyus seedlings grown in nutrient solution with 0-5 mM P. In addition, young leaves and roots of soil-grown plants were used for cryo-scanning electron microscopy and X-ray microanalysis. No P-toxicity symptoms were observed, even at 5 mM P in solution. Shoot DM was similar at 0.1 and 1.0 mM P in solution, but was ∼14% lower at 2 and 5 mM P. At 1 mM P, [P] was 36, 18, 14 and 11 mg P g(-1) DM in mature leaves, young leaves, stems and roots, respectively. Leaf potassium, calcium and magnesium concentrations increased with increasing P supply. Leaf epidermal and palisade mesophyll cells had similar [P]. The root epidermis and most cortical cells had senesced, even in young roots. We conclude that preferential accumulation of P in mature leaves, accumulation of balancing cations and uniform distribution of P across leaf cell types allow P. polystachyus to tolerate very high leaf [P].
authors.affiliation: School of Plant Biology and Institute of Agriculture, University of Western Australia, Crawley, Western Australia, 6009, Australia; Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, 38040, Pakistan.
authors.forename: Tariq
authors.initials: T
authors.lastname: Aziz
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
authors.forename: Dion
authors.initials: D
authors.lastname: Nicol
authors.forename: Megan H
authors.initials: MH
authors.lastname: Ryan
mesh_terms: D027703:Amaranthaceae / Q000502:physiology* / Q000648:ultrastructure; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D004577:Electron Probe Microanalysis; D008274:Magnesium / Q000378:metabolism*; D009928:Organ Specificity; D010758:Phosphorus / Q000378:metabolism*; D018515:Plant Leaves / Q000502:physiology / Q000648:ultrastructure; D018520:Plant Shoots / Q000502:physiology / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism*; D036226:Seedlings / Q000502:physiology / Q000648:ultrastructure; D013455:Sulfur / Q000378:metabolism
chemical_list: D010758:Phosphorus; D013455:Sulfur; D008274:Magnesium; D011188:Potassium; D002118:Calcium
keywords: Australian native herb; X-ray microanalysis; cell-specific phosphorus accumulation; phosphorus toxicity; phosphorus-use efficiency; root cortex shedding