Relationships between cell wall composition and leaf development in low-P mashbean (Vigna aconitifolia) plants

Abstract

Mashbean (Vigna aconitifolia) plants were grown on P-deficient soil (Granite Regosol) at P application levels of 5 (Low P) and 80 kg P ha-1 (Control). Data were collected for whole plant dry weight, leaf number, leaf area, and P content three times during the vegetative growth. Newly initiating leaves were tagged both in low-P and control plants, and sampled for the determination of average leaf area and P content at 5, 10, and 15 days after laminae unfolding. Developing leaves as described above in both low-P and control plants were sampled fresh into methanol, cell wall material was isolated and its dry weight and P content determined. The results indicated that leaf number, leaf area, and whole plant dry weight and shoot P content were extremely reduced in low-P than in control plants (data not shown). The P content and leaf area expansion were greatly reduced in developing leaves of low-P than control plants when sampled at 5, 10, and 15 days after laminae unfolding. The dry weight of cell walls of the developing leaves was reduced in low-P than in control plants. A lower P content in the cell walls in the developing leaves of low-P plants was indicated compared to control plants. From these results, it is assumed that low P application inhibited leaf expansion through reduction in the synthesis of cell wall components.