Carbon and nitrogen assimilation, and growth of moongbean (Vigna radiata [L.] Wilczek) cultivars grown under sulfur regimes

Abstract

Sulfur (S) has become an essential macronutrient for plants but its deficiency in agricultural soil is increasing worldwide. In a greenhouse pot-experiment the influence of S availability (0 and 40 mg S kg⁻¹ soil) on some growth and physiological attributes and their relationships was determined in two cultivars (Pusa 9531 and PS 16) of moongbean (Vigna radiata [L.] Wilczek) at 20 and 40 days after sowing (DAS). Sulfur deficiency translated as decreased plant dry mass (PDM), leaf area (LA), net photosynthesis (P_N), nitrate reductase activity (NRA), contents of chlorophyll (Chl), soluble protein and leaf sulfate (SO₄ ²⁻). These changes were in correspondence with significant increase in contents of leaf nitrate (NO₃ ⁻) and free amino acids being more pronounced in cultivar PS 16 than Pusa 9531. The relationship of NRA with plant dry mass and P_N was worked out in both cultivars. Pusa 9531 significantly maintained the coordination between C and N assimilation and hence, the plant growth under S-deficient condition. The information may be useful in breeding moongbean cultivars.

Keywords:

• carbon and nitrogen assimilation
• moongbean
• nitrate reductase activity
• photosynthesis
• sulfur regimes

Acknowledgements

The first author is deeply indebted to Hamdard National Foundation (HNF), New Delhi, India, and to the American Foundation for Muslims from India (AFMI) for financial assistance for the work. Authors wish to thank Dr Altaf Ahmad, for critical reading of the manuscript and helpful discussion and Drs Naresh Chandra and JL Tickoo, scientists at Pulses Breeding Section, Division of Genetics of Indian Agriculture Research Institute (IARI), New Delhi, India, for providing authentic moongbean seeds.