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.