Seeds of Kosteletzkya virginica (Malvaceae): their structure,germination, and salt tolerance. II. Germination and salt tolerance

Kosteletzkya virginica (L.) Presl. (Malvaceae) is a perennial that grows in saline or brackish water, and is salt-tolerant in its mature state, but less tolerant during germination. The seeds show a very low permeability to water that increases during storage. The permeability to water differs in seeds harvested in different years. Optimal temperature for germination is 28–30 C. The effect of salinity on imbibition is largely osmotic, but germination is inhibited, apparently, by the combined osmotic and “ionic” effects, especially at high NaCl concentrations. Inhibition of germination by high NaCl concentrations is relatively more severe in scarified than in intact seeds, indicating that the seed coat acts as a partial barrier to Na⁺ influx. External application of proline or betaine did not improve germination under saline conditions. Dry seeds contain a significant amount of betaine and low levels of proline, but during germination and in the presence of NaCl the betaine content decreased while the proline content increased. Thus, the likely compatible solute in the germinating seed seems to be proline.