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Summary The physiological responses of a tolerant (ICPL 227) and a sensitive (HY 3C) cultivated pigeonpea [Cajanus cajan (L.) Millsp.] genotype and of tolerant (Atylosia albicans, A. platycarpa and A. sericea) and sensitive (Rynchosia albiflora, Dunbaria ferruginea, A. goensis and A. acutifolia) wild relatives were examined over a range of salinity levels. Transpiration rate decreased with increasing salinity in tolerant and sensitive pigeonpea genotypes and there were no consistent differences between them in this respect. Although leaf proline concentrations increased under salinity in the cultivated pigeonpea and in some of the wild relatives, there was no relation between salinity tolerance and proline accumulation. The greater salinity tolerance of A. albicans, A. platycarpa and A. sericea was associated with efficient sodium and chloride regulation in the plant system. Shoot sodium concentrations of the tolerant wild species were five to ten times less than those of the sensitive species, while root sodium concentrations in the tolerant species were two to three times higher than in the sensitive species. The potassium concentrations in the tolerant species increased with salinity, while in the sensitive species they decreased. Leaf magnesium concentrations remained unaffected with increasing salinity in the tolerant species, while in most of the sensitive species they decreased. Thus efficiency of regulation of ion transport to shoots seems to explain the differences in salinity response among pigeonpea genotypes and related wild species. |
