Effect of temperature, salinity and water potential on seed germination of annual grass Stipa capensis

Abstract

The effect of water stress, salinity and temperature on the germination of Stipa capensis seeds were estimated herein. Seed germination was determined over different temperatures (10 °C, 15 °C, 20 °C, 25 °C and 30 °C), across a range of osmotic potentials of the polyethylene glycol solutions (0.0; −0.2; −0.5; −0.8; −1.6 MPa) and four salinity levels (0, 50; 100; 150 mmol/l−1) in four replicates of 50 caryopses for a period of 20 d. Results showed that temperature significantly affected the germinative percentage of Stipa capensis seeds (p < .001). The optimum temperature was 20 °C. The final germination percentage increased at the sub-optimal temperature range (10 °C–20 °C). However, from 20 to 30 °C, the final germination percentage decreased. The base temperature (Tb) was thus determined at 11.36 °C and the ceiling temperature (Tc) at 31.55 °C. Moreover, the highest germination percentage was found in osmotic potential 0 MPa (81 ± 2.4%). The increase in PEG6000 concentration resulted in an important decrease of germination percentage, with only 40% of seeds germinating at 0.8 MPa. Stipa capensis was also sensitive to high salinity (150 mmol/l−1) with a 29 ± 1.5 germination percentage. Overall, the study has shown the ability of Stipa capensis seed to germinate under low temperatures, water and salt stress that characterize most arid and semi-arid regions.