Effect of ethephon and gibberellin A3 on Amaranthus caudatus seed germination and alpha- and beta-amylase activity under salinity stress

This study assessed the effects of different doses of ethephon and gibberellin A3 on germination and α- and β-amylase activity in Amaranthus caudatus seeds exposed to different levels of salt stress. NaCl at 25 and 50 mM only delayed germination; at 75, 100 and 125 mM it caused 50%, 90% and 99.5% inhibition of Amaranthus caudatus seed germination. Both ethephon and GA3 (0.01, 0.1, 0.3 mM) effectively counteracted inhibition of seed germination under salinity. The stimulatory effect of ethephon appeared earlier, and the seeds were more sensitive to ethephon than to GA3. Ethephon enabled seed germination in the presence of all NaCl concentrations (75, 100, 125 mM) even after 24 h. GA3 alleviated inhibition caused by 75 and 100 mM NaCl until 48 h and did not affect reduction of germination caused by NaCl at 125 mM. NaCl (100 mM) reduced α- and β-amylase activity and seed germination after 14 h, and enhanced α-amylase activity after 20 h, although germination was reduced. Ethephon and GA3 increased α- but not β-amylase activity under salt stress during the first 14 h of incubation