Effects of Plant Growth Regulators on Seed Germination and Biochemical Properties of Two Wheat Cultivars Under Water Deficit Conditions

Drought stress limits wheat production. Plant growth regulators (PGRs) may help decrease the harmful effects of drought stress on seed germination and plant growth. Therefore, two experiments investigated growth regulators' effects on wheat germination and biochemical characteristics. The first experiment was conducted as a factorial based on a completely randomized design with three replications on germination. The factors were the moisture levels 0 (non-stress), -0.4 and -0.8 MPa, two wheat cultivars (Sirvan and Homa), and the PGRs solutions used for seed priming, including control (non-priming), gibberellic acid (100 mu m), cytokinin (100 mu m) and cycocel (3 gr lit(-1)). The second experiment was a hydroponic experiment carried out as a factorial design with three replications. The factors were the same osmotic stress treatments, the same cultivars, and similar four levels PGRs as a foliar application. The highest root length (RL), shoot length (SL), and germination rate (GR) were recorded in Homa cultivar by priming with GA3 under non-stress conditions. Homa seeds primed with CCC recorded the highest root-to-shoot ratio (R/S) at -0.8 MPa. Germination percentage (GP) and GR were higher in this cultivar than in Sirvan. In the hydroponic experiment, drought stress significantly affected all traits. Drought stress reduced soluble protein (SP), whereas other traits increased. PGRs decreased malondialdehyde (MDA) and enhanced polyphenol oxidase (PPO), superoxide dismutase (SOD), proline (PRO), SP, and glycine betaine (GB) content. Therefore, PGRs can be considered an alternative way to alleviate the effect of drought stress on wheat germination and seedling growth.