Effects of exogenous gibberellic acid 3 and cold stratification on seed dormancy and germination in Cephalotaxus sinensis

Cephalotaxus sinensis seeds often fail to germinate, even under favorable environment conditions. Some studies have shown that cold stratification and the application of gibberellic acid (GA) can break seed dormancy and promote seed germination. To investigate the effect of cold stratification and different concentrations of exogenous GA₃ on seed germination of C. sinensis, we measured germination rates and changes in soluble sugar, starch, amylase, soluble protein, free amino acids, and endogenous hormones on plants treated with GA₃ and cold stratification. Seeds that were stratified for five months had germination rates of 12.7%, while those cold stratified and also treated with 200, 400, or 600 mg/L of GA₃ had germination rates of 29.2%, 21.7% and 18.4%, respectively. Cold stratification resulted in a significant enhancement in free amino acid content, whereas soluble sugar content decreased the first 45 d and then increased constantly until the end of the study period. Cold stratification resulted in decreases in plant reserves, including starch and protein, but increases in the activities of α-amylase and α + β-amylase. Endogenous GA and IAA (indole-3-acetic acid) content increased, while ABA (abscisic acid) content decreased over the experiments. ZR (Zeatin riboside) content decreased in the early phase of cold stratification, but rebounded by the end of the experimental period.