Subcellular distributions of phosphorus and calcium in arsenic hyperaccumulator Pteris vittata L. and its tolerance to phytotoxicity of arsenic
砷超富集植物蜈蚣草中磷和钙的亚细胞分布及其与耐砷毒的关系

The subcellular distributions of phosphorus (P) and calcium (Ca) in Pteris vittata L., an arsenic (As) hyperaccumulator, were examined to explore the mechanisms of As tolerance of these plants grown under sand culture conditions. The results indicated that more than 44% of P was localized in the cytoplasmic supernatant fractions in roots, petioles and pinnae, and 48% of the absorbed Ca was localized in the plant cell walls. Calcium treatments (5.0 mmol·L-1) enhanced significantly P contents in root cytoplasmic supernatants and in petiole organelle fractions. Moreover, the Ca contents in each P. vittata L. subcellular fraction were enhanced with subsequent Ca additions to the culture media. These findings indicate that Ca may interfere with the normal physiological nutrient metabolism of P and Ca, and with plant growth rates. The amount of P bound to the organelles aboveground increased with additional As treatments, and the percentage of P accumulation in the shoot organelle fractions of P. vittata L. was also enhanced. However, the P contents in the root and petiole cell wall fractions decreased to some extent. Added As also increased the Ca content root cell wall fractions, which may help maintain cell wall stability. Thus, the subcellular distributions of P and Ca acclimated to As stress may help P. vittata L. tolerate As phytotoxicity, and maintain its normal growth rate.