Comparative salinity tolerance of two legumes, Vigna luteola and Vigna vexillata, from the coast of Trinidad

Abstract

The germination and growth responses of two legumes, Vigna luteola and Vigna vexillata, to different salinity levels were compared in laboratory experiments. Vigna luteola seeds tolerated a higher level of salinity and germinated significantly better at high salinities than corresponding results for V. vexillata. Seedlings of V. luteola exhibited a significant increase in dry weight at 10% sea water followed by a significant decrease at 30% seawater and above. Vigna vexillata seedlings showed a gradual decrease in dry weight with increased salinity. Except at 0% seawater, dry weights of V. luteola seedlings were significantly higher than those of V. vexillata at all salinities tested. The proportion of root weight to total plant dry weight increased with increased salinity in V. luteola; the reverse was the case in V. vexillata. In both species, increased salinity resulted in increased sodium content but decreased potassium and calcium contents. While the sodium content of the shoot of V. vexillata was higher than that of V. luteola, the amount in the roots of V. luteola was higher. The potassium and calcium contents were higher in V. luteola than in V. vexillata and the sodium to potassium ratio values were lower in V. luteola than in V. vexillata. The results are compared with those of other legumes and discussed in relation to the habitats of the species, the characteristics of halophytes, and the uses which these legumes may have in salt-enriched lands. Key words: salinity, tolerance, germination, growth, Vigna.