Influence of Exogenous Application of Glycinebetaine on Reducing the Effect of Drought Stress at Germination and Early Seedling Growthof Corn (Zea mays L.)

In order to evaluate the effect of seed treatment with glycinebetaine, a factorial experiment with 5 glycinebetaine levels (0, 2, 4, 8 and 16 mM) and 6 drought stress levels (0, -0.1, -0.2, -0.4, -0.8 and -1 MPa) was conducted based on completely randomized design with 3 replications. Corn seeds were immersed in water for 24 hours at corresponding glycinebetaine concentrations. These seeds were placed in petri dish and were exposed to different drought stress levels using PEG 6000. Results showed that drought stress caused a significant reduction in all measured parameters at different glycinebetaine concentrations. However, glycinebetaine concentrations of 2 and 4 mM effectively decreased the drought stress impact on seeds. Seed treatment with glycinebetaine, however, could not alleviate the effect of drought stress on germination rate. The three-parameter logistic model fitted to germination percentage effectively successfully justified the advantageous effect of seed treatment with glycinebetaine under drought stress. According to the model estimation, the drought level which causes 50% reduction in germinability was happened at higher drought stress levels when seeds were treated with glycinebetaine. Seed treating with glycinebetaine could alleviate the effect of drought stress on germination percentage, radicle and coleoptile length and fresh weight. Nevertheless, increasing the glycinebetaine concentration above 8 mM negatively affected germination and related parameters.