Abstract
Auxillary bud cultures of two cassava (Manihot esculenta Crantz) cultivars, UWI-1 and UWI-2, were subjected to salt stress using levels of crude sea salt varying from 0 g to 10 g L-1. Plantlets were allowed to develop and grow for eight weeks and shoot height, number of nodes and branches, levels of proline in leaf, stem, and root, levels of protein, soluble carbohydrate, Na and K in shoot (leaf plus stem) and root, and the activity of the enzyme nitrate reductase in the root and shoot were measured. Salinity levels up to 4 g L-1 were tolerated by cv. UWI-1 while cv. UWl-2 was tolerant up to 6 g L-1. Low concentrations of salts increased the proline content in the stem and leaf but not in the root. Concomitant with this, the levels of soluble carbohydrates decreased in the roots while there was not much change in the protein content. The levels of Na and K also increased. The activity of the enzyme nitrate reductase decreased in the shoot while in the roots, the activity was not affected or in some cases it increased. The present results indicated that in the two cassava cultivars, UWI-1 and UWl-2, salt stress was countered by increased influx of K and synthesis of proline and increased synthesis of carbohydrates in the shoot. It appears that cv. UWI-2 is more tolerant to salt stress than cv. UWI-1.
