Response of Sophora alopecuroides and Thermopsis lanceolata seed germination and growth to drought stress

Seed germination and seedling stages are not only crucial stages of the life span of plants, but also important adaptation stages to different environmental conditions. The response of Sophora alopecuroides L. and Thermopsis lanceolate L. seed germination and seedling growth to drought stress in border desert lands of the Hexi Corridor were investigated under simulated drought conditions of polyethylene glycol-6000 (PEG) with -0.03 MPa, -0.10 MPa, -0.24 MPa, -0.42 MPa, -0.65 MPa and -0.94 MPa osmotic potentials. The main objectives of the study were to reveal the adaptive mechanisms of desert plants and to provide further technical guidance on seedling cultivation and restoration of desert vegetation. The result showed that the rate of seed water uptake, germination percentage, germination index, vigor index, seedling height, root length and plant water content decreased with increasing PEG drought stress. However, seedling and root dry weight and root/shoot ratio initially increased followed by a decrease. Furthermore, seed germination was sensitive to drought stress. The lowest osmotic potential threshold was -0.65 MPa for S. alopecuroides seeds and -0.42 MPa for T. lanceolate seeds. For seeds incapable of germination under drought stress, germination percentage was high once water was recovered. The results suggested that response of seed germination and seedling growth to drought stress was ecologically essential for later establishment of seedlings and vegetation. In artificial cultivation, however, a key step for successful planting was guaranteed soil moisture.