Seed Priming with Gibberellin Regulates the Germination of Cotton Seeds Under Low-Temperature Conditions

Exogenous substances play an important role in the response of cotton to low-temperature conditions during the germination stage, but little is known about the mechanism involved. To fill this knowledge gap, experiments were conducted to clarify the effects of the application of exogenous substances on the germination, storage substances, endogenous hormones and activities of antioxidant enzymes after gibberellin (GA 3 ) treatment under low-temperature conditions. The results showed that in XinLuZao65 (L) under low-temperature conditions, all exogenous substances tested increased the germination potential (GP) and germination index (GI) and decreased the mean time of germination (MTG), but GA 3 , 2,4-epibrassinolide (EBR), methyl jasmonate, fluridone, and salicylic acid elevated the germination rate in this variety. In XinHai35 (H) at 12 °C, exogenous substances increased the GI and decreased the MTG, but only EBR, hydrogen sulfide, and nitric oxide decreased the GP of this variety, whereas exogenous GA 3 had the best effect on seed germination at low temperature. After exogenous GA 3 and low-temperature treatment, the activities of superoxide dismutase and lipase, the contents of maize riboside, GA 3 and indole-acetic acid in cotton seeds were higher than those in the control, while the peroxidase (POD), catalase (CAT), and amylase activities and the contents of abscisic acid (ABA), malondialdehyde, hydrogen peroxide (H 2 O 2 ), starch, total sugars and total proteins were lower than those of the control. Correlation analysis revealed that ABA, adipose, CAT, H 2 O 2 , POD, GA 3 and GA 3 /ABA were the main factors affecting the germination of cotton seeds at low temperature. Therefore, exogenous GA 3 regulates the balance of endogenous hormones, enhances the activities of key enzymes, and reduces the accumulation of active oxygen, thereby accelerating the metabolism and conversion of materials and improving the low-temperature tolerance of cotton seeds during the germination stage.