Phosphorus toxicity in the Proteaceae: A problem in post-agricultural lands Export

@article{citeulike:3031933, abstract = {South African Proteaceae are adapted to the low soil phosphorus (P) concentrations of the Cape Floristic Region. The efficient P uptake by Proteaceae means that these plants experience phosphorus (P) toxicity at lower rhizosphere [P] than crop plants. This is only problematic when cultivating Proteaceae (and many plants from this region) on previously agricultural land with high residual soil [P]. In this study we hypothesize that P toxicity will result in element imbalances in leaves of Proteaceae and information from this study aims to facilitate ameliorative treatments. Phosphorus toxicity was induced on-farm in Leucadendron [`]Safari Sunset' (Proteaceae) with subsequent mapping of element distribution in non-necrotic leaf tissue using micro particle-induced X-ray emission spectrometry. Phosphate supply up to 0.01 mM in a fertigation solution resulted in increased stem length of Leucadendron [`]Safari Sunset' while P concentrations in excess of this resulted in decreased stem length, increased leaf [P] up to 0.25\% (w/w) and, between 1 mM and 5 mM P supply, typical P toxicity symptoms were observed. High P supply (5 mM P) resulted in increased leaf [P] in most leaf tissues including the epidermis, where calculations from an equilibrium speciation model indicated that there was 30\% more dissolved PO43- in the epidermis compared to leaves at low P supply (0 mM added P on soil with 34 mg P kg-1). Concomitantly, bundle sheath and epidermal [Ca] were reduced and 10\% more Ca was predicted to be adsorbed and precipitated as hydrapatite at high P supply. High P supply resulted in increased leaf [Cl] and [Mn] in all tissues studied; decreased total leaf [Fe], bundle sheath, xylem, phloem and epidermal [Fe] and decreased total leaf [Zn] and xylem and phloem [Zn]. The observed symptoms of P toxicity in Leucadendron [`]Safari Sunset' (necrosis in some plants, chlorosis and leaf rosetting) co-occurred with (1) excess PO43-, which may bind Ca in the epidermis (leading eventually to necrosis); (2) reduced [Fe] and increased [Mn] (leading to chlorosis) and (3) reduced total and vascular [Zn] (leading to leaf rosetting).}, author = {Hawkins, Heidi-Jayne and Hettasch, Hans and Mesjasz-Przybylowicz, Jolanta and Przybylowicz, Wojciech and Cramer, Michael D.}, citeulike-article-id = {3031933}, citeulike-linkout-0 = {http://dx.doi.org/10.1016/j.scienta.2008.05.001}, citeulike-linkout-1 = {http://www.sciencedirect.com/science/article/B6TC3-4SYDB0T-1/1/41ae7d4eb5351d9b04bc1b820b0d6ea8}, doi = {10.1016/j.scienta.2008.05.001}, journal = {Scientia Horticulturae}, keywords = {agriculture, fertility}, posted-at = {2008-07-22 07:35:54}, priority = {0}, title = {Phosphorus toxicity in the Proteaceae: A problem in post-agricultural lands}, url = {http://dx.doi.org/10.1016/j.scienta.2008.05.001}, volume = {In Press, Corrected Proof} }

TY - JOUR ID - citeulike:3031933 L3 - citeulike-article-id:3031933 N2 - South African Proteaceae are adapted to the low soil phosphorus (P) concentrations of the Cape Floristic Region. The efficient P uptake by Proteaceae means that these plants experience phosphorus (P) toxicity at lower rhizosphere [P] than crop plants. This is only problematic when cultivating Proteaceae (and many plants from this region) on previously agricultural land with high residual soil [P]. In this study we hypothesize that P toxicity will result in element imbalances in leaves of Proteaceae and information from this study aims to facilitate ameliorative treatments. Phosphorus toxicity was induced on-farm in Leucadendron [`]Safari Sunset' (Proteaceae) with subsequent mapping of element distribution in non-necrotic leaf tissue using micro particle-induced X-ray emission spectrometry. Phosphate supply up to 0.01 mM in a fertigation solution resulted in increased stem length of Leucadendron [`]Safari Sunset' while P concentrations in excess of this resulted in decreased stem length, increased leaf [P] up to 0.25% (w/w) and, between 1 mM and 5 mM P supply, typical P toxicity symptoms were observed. High P supply (5 mM P) resulted in increased leaf [P] in most leaf tissues including the epidermis, where calculations from an equilibrium speciation model indicated that there was 30% more dissolved PO43- in the epidermis compared to leaves at low P supply (0 mM added P on soil with 34 mg P kg-1). Concomitantly, bundle sheath and epidermal [Ca] were reduced and 10% more Ca was predicted to be adsorbed and precipitated as hydrapatite at high P supply. High P supply resulted in increased leaf [Cl] and [Mn] in all tissues studied; decreased total leaf [Fe], bundle sheath, xylem, phloem and epidermal [Fe] and decreased total leaf [Zn] and xylem and phloem [Zn]. The observed symptoms of P toxicity in Leucadendron [`]Safari Sunset' (necrosis in some plants, chlorosis and leaf rosetting) co-occurred with (1) excess PO43-, which may bind Ca in the epidermis (leading eventually to necrosis); (2) reduced [Fe] and increased [Mn] (leading to chlorosis) and (3) reduced total and vascular [Zn] (leading to leaf rosetting). JF - Scientia Horticulturae TI - Phosphorus toxicity in the Proteaceae: A problem in post-agricultural lands VL - In Press, Corrected Proof KW - agriculture KW - fertility AU - Hawkins, Heidi-Jayne AU - Hettasch, Hans AU - Mesjasz-Przybylowicz, Jolanta AU - Przybylowicz, Wojciech AU - Cramer, Michael UR - http://dx.doi.org/10.1016/j.scienta.2008.05.001 ER -