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

为了在研究砷超富集植物蜈蚣草中磷和钙的亚细胞分布,并探讨其与蜈蚣草耐砷毒的关系进行了试验研究.结果表明,蜈蚣草吸收的磷主要分布在胞质组分中(平均占各部位总磷含量的44%以上),吸收的钙主要分布在细胞壁组分中(平均占各部位总钙含量的48%以上).与低钙(0.03和2.5 mmol·L-1)处理相比,高钙(5.0 mmol·L-1)处理时,根部的胞质组分和叶柄的细胞器组分中磷含量较高.各器官的亚细胞组分中钙含量随着介质中添加钙浓度的提高而增加.介质钙浓度过高会抑制蜈蚣草的生长.在加砷处理下,根部和叶柄细胞壁组分的磷含量有所减少,但地上部细胞器组分的磷含量及其含磷总量占植株含磷总量的相对比例、根部细胞壁组分的钙含量增加.蜈蚣草自主调节磷和钙的亚细胞水平分布可能是其耐砷毒的机制之一.

Subcellular distributions of phosphorus and calcium in arsenic hyperaccumulator Pteris vittata L. and its tolerance to phytotoxicity of arsenic

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.