DRY-MATTER YIELD, N-15 ABSORPTION, AND WATER-UPTAKE BY GREEN BEAN UNDER SODIUM-CHLORIDE STRESS

Nutrient absorption and water uptake by plants seem to be impaired under salt stress, resulting in abnormal growth and lower yields. Plant types and species behave differently under stress conditions. Therefore, to select the most suitable green bean (Phaseolus vulgaris L.) cultivar for optimum dry-matter yield and N and water uptake patterns, the cultivars Tender Improved, Slim Green, and Kentucky Wonder were compared using N-15 under three NaCl levels (-0.03 [control], -0.25, and -0.50 MPa osmotic potentials). Five days after the start of incubation, seedlings were exposed to light for 7 d and allowed to grow for an additional 7 d in complete Hoagland solution before and 7 d after completion of salt treatments. This was followed by a 15-d N-15-uptake period after ammonium nitrate ((NH4)-N-15(NO3)-N-15) addition to nutrient solutions. Nitrogen-15 was used to determine precisely the amount of N taken up by these cultivars specifically during NaCl stress period. Dry-matter yield was determined and shoots and roots analyzed for total N and N-15 uptake and distribution. Dry-matter production, total N and N-15 absorption, and water uptake decreased with increasing salinity for all cultivars, but Tender Improved was least severely affected by NaCl stress, probably due to its higher salt tolerance. The -0.25-MPa stress caused > 25% reduction in each of these components for each cultivar at each harvest. This value was > 50% at -0.50 MPa osmotic potential. Based on the results of this investigation and under comparable conditions, Tender Improved seems the most suitable among these cultivars for growing under field conditions.