Effects of osmotic stress on sorghum (Sorghum bicolor L. Moench) seed germination and embryo growth.

Romania is one of the European countries with vast areas of low productivity soils containing toxic salts, being frequently associated with poverty. The problems determined by osmotic stress are associated mostly with other abiotic stress factors, as drought and phosphorus deficit. The osmotic potential of a colloidal solution can mimic the soil water potential, and that is a most important parameter in controlling seed germination under normal farming conditions. The effects of osmotic stress on seed germination and early embryo growth were investigated in laboratory in three cultivars of sorghum – cv. “F135ST”, cv. „Sugargraze I” and „Sugargraze II”– to verify how stress may limit crop growth during the very early stages of growing season. Two water potentials (ψ) of the germination solution (from 0 to-0,3 and -0,6 MPa) in polyethylene glycol (PEG-6000) for osmotic stress tests were studied. The experimental design was Completely Random Design (CRD), which was based on factorial with 3 replications. In the experiment, seeds were germinated in covered, sterilized, disposable Petri dishes. Daily germination was recorded, radicle and shoot lengths were measured during 7 days after initial germination. Seed germination was reduced in stress conditions, and shoot/ root growth was adversely affected. Four parameters, namely germination percentage, germination rate, germination index and coefficient velocity of germination were estimated. The results of this study showed that different levels of the osmotic stress had significantly affected the germination percentage, germination rate, germination index and coefficient velocity of germination. The evaluation of the three varieties showed that F135ST (V1) had a higher germination percentage (89%) than the Sugargraze I (86%) and Sugargraze II (76,66%).The maximum germination index (624) and coefficient velocity of germination (74,88) were retrieved from F135ST. The cultivar with the longest coleoptil at the highest PEG concentration was F135ST and radicle at