Diagnosis of Sulfur Status of Winged Bean [Psophocarpus Tetragonolobus (L.) Dc] by Plant Tissue Analysis

Abstract

Winged bean [Psophocarpus tetragonolobus (L.) DC] plants, line UPS31, were grown in pots of sulfur (S)-deficient soil in a glasshouse without added S or with five levels of added S. The seed was inoculated with rhizobia (Bradyrhizobia sp. strain CB756) and plants were later given additional mineral nitrogen (N). Harvests of shoots were made at 39 and 78 days after sowing (DAS). Shoot dry matter yield, total S (S_T), S reducible by hydriodic acid (S_HI) – a measure of sulfate – and N were determined. At 78 DAS, the critical concentration (at 90% maximum yield) of S_T in shoots was 0.9 mg S g⁻¹ dry matter and in young leaves was 1.4 mg S g⁻¹ dry matter. Plants with these concentrations or below would be considered S-deficient. The usefulness of critical concentrations of S_HI or ratios of S_HI/S_T, and N/S_T as indicators of S status is discussed.

Keywords:

• sulfur deficiency
• winged bean
• diagnosis
• sulfur concentration
• reducible-sulfur concentration