SEEDS OF KOSTELETZKYA-VIRGINICA (MALVACEAE) - THEIR STRUCTURE, GERMINATION, AND SALT TOLERANCE .2. GERMINATION AND SALT TOLERANCE

Kosteletzkya virginica (L.) Presl. (Malvaceae) is a perennial that gro ws in saline or brackish water, and is salt-tolerant in its mature sta te, but less tolerant during germination. The seeds show a very low pe rmeability to water that increases during storage. The permeability to water differs in seeds harvested in different years. Optimal temperat ure for germination is 28-30 C. The effect of salinity on imbibition i s largely osmotic, but germination is inhibited, apparently, by the co mbined osmotic and ''ionic'' effects, especially at high NaCl concentr ations. Inhibition of germination by high NaCl concentrations is relat ively more severe in scarified than in intact seeds, indicating that t he seed coat acts as a partial barrier to Na+ influx. External applica tion of proline or betaine did not improve germination under saline co nditions. Dry seeds contain a significant amount of betaine and low le vels of proline, but during germination and in the presence of NaCl th e betaine content decreased while the proline content increased. Thus, the likely compatible solute in the germinating seed seems to be prol ine.