Foliar Application of Gibberellin Alleviates Adverse Impacts of Drought Stress and Improves Growth, Physiological and Biochemical Attributes of Canola (Brassica napus L.)

Under the current climate change scenario, water stress is one of the key factors that reduce the production of crops. Gibberellic acid (GA3) is an efficient endogenous plant hormone that shows a vital role in plant growth and development. Production of canola (Brassica napus L.) and its oil contents are severely affected under drought stress. The present study was conducted to investigate the potential of GA3 in alleviating drought stress in canola. Three levels of GA3 (G0 = 0 mg L−1, G1 = 100 mg L−1, and G2 = 150 mg L−1) as foliar applications were applied under two drought-stress conditions (D1 for three days of drought stress and D2 for six days of drought stress) on two canola varieties (Punjab canola and Faisal canola). Irrigation was applied after 3 weeks of germination, while foliar application of GA3 was done at intervals of 4 and 5 weeks after germination. When comparing the output of all the GA3 treatments, it was noticed that in G0 = 0 mg L−1 (control plants), water-stress conditions markedly reduced plant production and seed oil contents but increased protein and linoleic acid. With the application of G2 = 150 mg L−1, the maximum values of plant height (90.83 cm), no. of siliqua plant−1 (15.50), seed siliqua−1 (15.55), siliqua length (5.08 cm), relative water contents (77.60%), yield plant−1 (0.46 g), chlorophyll a (0.62), carotenoid contents (39.52), and oleic acid contents (60.20) were recorded under drought stress. Based on these results, it is concluded that the adverse effect of drought stress on different yield parameters of canola could be ameliorated by the exogenous application of GA3 through foliar application at a dose of 150 mg L–1. Moreover, the same treatment improves the quality parameters, i.e., the oleic acid contents of the oil, obtained from the canola.