Seed priming improved germination, seedling quality and response to imposed drought stress in <i>Vachellia tortilis </i><i>subsp. spirocarpa</i> (Hochst. Ex A. Rich.)

Successful afforestation in arid lands requires rapid, uniform seed germination and good quality seedlings. Seed priming is a pre-treatment of seeds to improve germination and produce seedlings that withstand changing environmental conditions. Therefore, the present study aimed to test the effects of seed priming on Vachellia tortilis seed germination, nursery seedlings quality and the response of produced seedlings to imposed drought stress. Seed samples of V. tortilis were primed in three concentrations of osmo-priming solutions (polyethylene glycol (PEG-6000)) and three concentrations of hormonal priming solutions (Gibberellic acid (GA3)). Then, the effects were monitored during seed germination, nursery seedling development, and in the greenhouse under three successive cycles of drying and rewatering treatments. During germination, seed priming resulted in a higher total germination percentage (TGP), accelerated uniform germination (higher germination index (GI) and lower mean germination time (MGT)), and increased seedling vigour index (SVI). The recorded improvement in germination was associated with stimulation of antioxidant enzymes (peroxidase (POD) and polyphenol oxidase (PPO)) and hydrolytic enzymes (Polygalacturonase (PG) and α-amylase) activities in primed germinated seeds. While in the nursery, priming significantly improved the quality traits of seedlings, including root collar diameter, shoot-to-root ratio, sturdiness quotient, and Dickson’s quality index. GA3-300ppm, GA3-200ppm, and PEG-10% treatments resulted in increases in total dry weight of 160%, 121%, and 64%, respectively. The high-quality seedlings produced resulted in better growth and survival under imposed drought stress in the greenhouse. The findings concluded that seed priming is crucial for enhancing the germination and quality of V. tortilis seedlings.