Accumulation of phosphorus and calcium in different cells protects the phosphorus-hyperaccumulator Ptilotus exaltatus from phosphorus toxicity in high-phosphorus soils. (February 2021)

• Record Type: Journal Article
• Authors: Ye, Daihua; Clode, Peta L.; Hammer, Timothy A.; Pang, Jiayin; Lambers, Hans; Ryan, Megan H.
• Is Part Of: Chemosphere. Volume 264(2021)Part 1
• Publication Date: 2021-02
• Subjects: Ptilotus -- Phosphorus-hyperaccumulator -- High phosphorus tolerance -- Phosphorus toxicity -- Leaf phosphorus fractions -- Cell-specific allocation; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.128438
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Ptilotus exaltatus accumulates phosphorus (P) to > 40 mg g -1 without toxicity symptoms, while Kennedia prostrata is intolerant of increased P supply. What physiological mechanisms underlie this difference and protect P. exaltatus from P toxicity? Ptilotus exaltatus and K. prostrata were grown in a sandy soil with low-P, high-P and P-pulse treatments. Both species hyperaccumulated P (>20 mg g −1 ) under high-P and P-pulse treatments; shoot dry weight was unchanged for P. exaltatus, but decreased by >50% for K. prostrata . Under high-P, in young fully-expanded leaves, both species accumulated P predominantly as inorganic P. However, P. exaltatus preferentially allocated P to mesophyll cells and stored calcium (Ca) as occasional crystals in specific lower mesophyll cells, separate from P, while K. prostrata preferentially allocated P to epidermal and spongy mesophyll cells, but co-located P and Ca in palisade mesophyll cells where granules with high [P] and [Ca] were evident. Mesophyll cellular [P] correlated positively with [potassium] for both species, and negatively with [sulfur] for P. exaltatus. Thus, P. exaltatus tolerated a very high leaf [inorganic P] (17 mg g -1 ), associated with P and Ca allocation to different cell types and formation of Ca crystals, thereby avoiding deleterious precipitation of Ca3 (PO4 )2 . It also showed enhanced [potassium] and decreased [sulfur] to balance high cellular [P]. Phosphorus toxicity in K. prostrata arose from co-location of Ca and P in palisade mesophyll cells. This study advances understanding of leaf physiological mechanisms for high P tolerance in a P-hyperaccumulator and indicates P. exaltatu s as a promising candidate for P-phytoextraction. Highlights: Ptilotus exaltatus and Kennedia prostrata were grown with low and high P supply. At high P supply, both species hyperaccumulated P, but only K. prostrata showed P toxicity. Both species accumulated leaf P mainly as inorganic P. Only P. exaltatus allocated P and Ca to separate cells in leaves.