Agrobotanical attributes, nitrogen-fixation, enzyme activities and nutraceuticals of hyacinth bean (Lablab purpureus L.): a bio-functional medicinal legume.

Hyacinth bean (Lablab purpureus L.) accessions of different origins received from USDA, ARS, Plant Genetic Resources Conservation Unit, Griffin, GA, USA were evaluated for agrobotanical attributes, enzyme activities, nutraceuticals and quality in calcium deficient soil of Aligarh, Western Uttar Pradesh, India. Fresh and dry weights per plant, leaf-area, number and dry weight of nodules per plant, net photosynthetic rate, stomatal conductance and transpiration rate, total chlorophyll and carotenoid content, activities of nitrate reductase and carbonic anhydrase, leaf - N, P, K and Ca contents and nodule-nitrogen and leghaemoglobin contents, respectively were analyzed at 60, 90 and 120 day after sowing. Photosynthesis was measured only at 90 DAS. Yield attributes including pod number per plant, seed number per pod, 100-seed weight and seed-yield per plant were recorded at harvest (150 DAS). Protein and carbohydrate content as well as tyrosinase activity in hyacinth bean seeds were also determined. Among the five accessions, EC-497619 (A4) showed superior performance over the rest of the accessions. Accession A4 showed the highest values for growth, yield, physiological, biochemical and quality attributes in comparison to the other accessions. Net photosynthetic rate, stomatal conductance and transpiration rate were found maximum in the A4 accession. Chlorophyll and carotenoid content were also reported higher in accession A4. Accession A4 showed higher nitrate reductase and carbonic anhydrase activities than the other accessions. Nodule-nitrogen and leghaemoglobin content ranged from 5.267-5.314% and 0.110-0.130 mM, respectively. Mineral profiles, viz., nitrogen, phosphorus, potassium and calcium content varied from 3.610-3.643, 0.338-0.356, 3.020-3.124 and 1.764-1.804%, respectively. Seed protein of all accessions varied from 24.70-25.06%. Carbohydrate content ranged from 50.83-53.16% across all accessions tested. Accession A4 produced the highest tyrosinase activity in the seeds.