Comparative Effects of Salt and Water Stress on Seed Germination and Early Embryo Growth in Two Cultivars of Sweet Sorghum

In semiarid regions of the Mediterranean basin, water and salinity stresses restrict crop establishment. The effects of salt and water stress on seed germination and early embryo growth (radicle and shoot growth) were investigated in laboratory in two cultivars of sweet sorghum [Sorghum bicolor (L.) Moench] - cv. '90-5-2? and cv. 'Keller' - to verify how these stresses may limit crop growth during the very early stages of growing season. Six water potentials (w) of the imbibition solution (from 0 to 1.0 MPa) in NaCl or polyethylene glycol (PEG) for salt and water stress tests, respectively, were studied. Daily germination was recorded, and radicle and shoot lengths and dry weights (DWs) were measured 2 days after initial germination. Seed germination was reduced (8-30% lower than control) by water stress at w <0.6 MPa and was delayed (approx. +10 h) already at 0.4 MPa. Salt stress only prolonged germination time. Shoot and root growth was adversely affected by water stress (PEG), whereas the effect of salt stress was less relevant. Cv. '90-5-2' was less sensitive than cv. 'Keller' to both stresses. These cultivars exhibited a greater sensitivity to abiotic stresses in terms of root and shoot growth; therefore, other parameters beside germination, such as early embryo growth rate, may help in evaluating sorghum lines for adaptation to semi-arid areas.