EFFECT OF SALINITY ON THE GROWTH OF THREE VARIETIES OF Sphenostylis stenocarpa (Hochst. Ex. A. Rich.) Harms (African yam bean).

ABSTRACT

The growth of three local varieties of Sphenostylis stenocarpa was evaluated in different concentrations of NaCl treated soils. The seeds of the three varieties were collected from Onitsha and Enugu towns. The study was carried out as potted field experiment and laid out as a completely randomized design with four NaCl treatments replicated five times overall growth. Sixty (60) experimental pots were prepared, 20 pots for each of the three coloured varieties; ash, brown and black coated seed varieties were used in the experiment. Treatment concentrations used in this study were 0mM, 150mM, 200mM and 250mM. Ten seeds were sown in each pot. Experimental data for plant growth measurements were collected for percentage germination, vine length, vine girth, number of leaves formed, number of days to flowering, fresh weight, dry weight and 100-seed weight. Other parameters include physicochemical analysis of composite soil sample used and elemental analysis (K⁺, Na⁺ and N) of the harvested seeds. Delay in germination of seeds in NaCl treated soil was observed only for the black coloured variety. On the average, germination was recorded three days after planting. The highest percentage germination was recorded in control soils. Salinity caused a reduction in the vine length of the plant. The highest values of vine length was observed in the control. It also caused a decrease in the values of all growth parameters recorded except that of vine girth. Increase in salinity also influenced the elemental content of the harvested seed causing an increase and decrease in the potassium and nitrogen content respectively, the sodium content was virtually unaffected. Thus, an indication that salinity affects the growth of Sphenostylis stenocarpa.