Effects of salt and drought stress on seed germination and seedling growth in Portulaca

摘要

The effects of salt and water deficit on seed germination and early seedling growth were studied insix Portulaca accessions (P. oleracea L. ssp. oleracea, P. grandiflora Hook., P. grandiflora cvs. ‘SundialMango’, ‘Double Pink’ and ‘Double White’, and P. halimoides L.). The aims of the study were to evaluatetheir responses to abiotic stress and to establish the relative degree of tolerance of the selected taxa. Seedswere germinated in the presence of increasing concentrations of NaCl or polyethylene glycol 6000 (tomimic drought conditions), generating the same osmotic potentials: 0, -0.25, -0.5 and -0.1 MPa.Germination percentage, mean germination time, seedling fresh weight and vigour index, and radicle,hypocotyl and cotyledon lengths were determined. Seed germination and seedling development decreasedin all taxa in the presence of PEG and NaCl, in a concentration-dependent manner, although the effect ofsalt was stronger than that of PEG, at the same osmotic potentials. Germination and seedling parametersvaried for the different accessions but, in practical terms, considering only the final germinationpercentages under stress, P. halimoides L. appears to be the taxon most tolerant to water deficit, whereasP. grandiflora Hook. would be the most tolerant to salt stress..