Changes of endogenous hormone content and enzyme activities during seed germination of Paris polyphylla

To investigate the germination physiological mechanism of Paris polyphylla seeds, different stages of the germination process were divided based on the seed embryo morphology and the changing rules in endogenous hormone content and related enzyme activities were analyzed at different stages. The results were as follows: (1) The germination process of the seeds could be divided into eight stages based on seed embryo morphology: non-germinating embryo stage (S1), heart-shaped embryo stage (S2), embryo swelling stage (S3), radicle not breaking through seed coat stage (S4), cotyledon petiole elongation and radicle breaking through seed coat stages (S5), lower hypocotyl breaking through seed coat stage (S6), upper hypocotyl elongation stage (S7), and radicle elongation stage (S8). (2) The α-amylase activity in the seeds was significantly higher than β-amylase activity at all germination stages. (3) Superoxide dismutase (SOD) activity was the highest at stage S5 and the lowest at stage S1; peroxidase (POD) and catalase (CAT) activities generally increased with seed germination progress; soluble protein content initially decreased and then increased with seed germination progress. (4) The contents of hormones such as indoleacetic acid (IAA), gibberellin (GA3), abscisic acid (ABA), and salicylic acid (SA) decreased overall, while 1-aminocyclopropane-1-carboxylic acid (ACC), jasmonic acid (JA), brassinolides (BRs) increased overall during seed germination. Cytokinins (CTKs) content showed no significant change. The ratios of IAA/ABA and GA3/ABA decreased initially and then increased, while CTKs/ABA continuously increased with seed germination progress. (5) The contents of ABA, IAA, GA3 were negatively correlated with embryo rate, while ACC, JA, BRs, POD, CAT, and β-amylase activity were positively correlated with embryo rate. In conclusion, the germination process of the seeds can be subdivided into eight stages based on seed embryo morphology, with varying endogenous hormone content and related enzyme activities at different stages. The activities of α-amylase and POD may be related to radicle elongation, while GA3 may affect the embryo formation, and ABA may inhibit the growth and development of the embryo.