title: Tissue and cellular phosphorus storage during development of phosphorus toxicity in Hakea prostrata (Proteaceae).
abstract: Storage of phosphorus (P) in stem tissue is important in Mediterranean Proteaceae, because proteoid root growth and P uptake is greatest during winter, whereas shoot growth occurs mostly in summer. This has prompted the present investigation of the P distribution amongst roots, stems, and leaves of Hakea prostrata R.Br. (Proteaceae) when grown in nutrient solutions at ten P-supply rates. Glasshouse experiments were carried out during both winter and summer months. For plants grown in the low-P range (0, 0.3, 1.2, 3.0, or 6.0 micromol d(-1)) the root [P] was > stem and leaf [P]. In contrast, leaf [P] > stem and root [P] for plants grown in the high-P range (6.0, 30, 60, 150, or 300 micromol P d(-1)). At the highest P-supply rates, the capacity for P storage in stems and roots appears to have been exceeded, and leaf [P] thereafter increased dramatically to approximately 10 mg P g(-1) dry mass. This high leaf [P] was coincident with foliar symptoms of P toxicity which were similar to those described for many other species, including non-Proteaceae. The published values (tissue [P]) at which P toxicity occurs in a range of species are summarized. X-ray microanalysis of frozen, full-hydrated leaves revealed that the [P] in vacuoles of epidermal, palisade and bundle-sheath cells were in the mM range when plants were grown at low P-supply, even though very low leaf [P] was measured in bulk leaf samples. At higher P-supply rates, P accumulated in vacuoles of palisade cells which were associated with decreased photosynthetic rates.
authors.affiliation: School of Plant Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Shane
authors.forename: Margaret E
authors.initials: ME
authors.lastname: McCully
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
mesh_terms: D002478:Cells, Cultured; D003300:Copper / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism* / Q000633:toxicity*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D018547:Plant Stems / Q000187:drug effects / Q000254:growth & development; D039105:Proteaceae / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013045:Species Specificity; D015032:Zinc / Q000378:metabolism
chemical_list: D010758:Phosphorus; D008345:Manganese; D003300:Copper; D007501:Iron; D015032:Zinc