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Tolerance of high phosphorus concentrations in Ptilotus exaltatus depends on the accumulation of phosphorus and calcium in different leaf cells
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  • Daihua Ye,
  • Peta Clode,
  • Timothy Hammer,
  • Jiayin Pang,
  • Hans Lambers,
  • Megan Ryan
Daihua Ye
Sichuan Agricultural University - Chengdu Campus
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Peta Clode
The University of Western Australia
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Timothy Hammer
The University of Western Australia
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Jiayin Pang
The University of Western Australia
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Hans Lambers
The University of Western Australia
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Megan Ryan
The University of Western Australia
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Abstract

Under very high phosphorus (P) supply, Ptilotus hyperaccumulates P without toxicity while Kennedia is intolerant. What physiological mechanisms underlie this difference? P. exaltatus and K. prostrata were grown in sandy soil with low- and high-P treatments. Under high P, both species hyperaccumulated P (>20 mg g–1) in leaves, and shoot dry weight was unchanged for P. exaltatus but decreased by >50% for K. prostrata. Under high P, both species preferentially accumulated leaf P as inorganic P but P. exaltatus preferentially allocated P to mesophyll cells and stored Ca as occasional crystals in specific lower mesophyll cells separate from P, while K. prostrata preferentially allocated P to epidermal and spongy mesophyll cells and co-located P and Ca in palisade mesophyll cells. Mesophyll cellular [P] correlated positively with potassium for both species and negatively with sulfur for P. exaltatus. High P tolerance arose from P and Ca allocation to different leaf cell types, formation of Ca crystals, and enhanced K and decreased S accumulation to balance high cellular [P]. Intolerance to high P arose from the co-location of Ca and P in palisade mesophyll cells. This study advances the understanding of leaf physiological mechanisms for high P tolerance in plants.