Study of rhizome characters and endogenous hormones of Trifolium ambiguum at different growth stages

Caucasian clover (Trifolium ambiguum) is the only perennial grass with the roots of the genus Trifolium. It has developed underground roots and a strong clonal growth ability. Plant growth on the Caucasus clover was analyzed at the regreening, branching, flowering, and full-blossom stages in this experiment. The rhizome and endogenous hormone content in different parts of the root system were determined. The results showed that 1) plant height, branching number, bundle number, and rhizome amplitude all increased with the growth over the growth period; the ratio of the height to amplitude was approximately 1 at all four stages. 2) Among different growth stages, the root hormone content was highest at the full-flowering stage. Compared with the total amount of different hormones in the same growth period, the IAA content was highest at the regreening and flowering (2.88 and 6.25 μg·g^–1, respectively). Compared to the total amount of different hormones in the same period, at the branching stage and full-blossom stages, the ABA content was highest (3.75 and 9.63 μg·g^–1, respectively). 3) Barring the flowering stage, the contents of GA₃, IAA, and ABA at the other three stages of swollen non-buds were higher than those of swollen buds. Three kinds of hormones reacted together to inhibit the burgeoning of rhizome buds in swollen parts. IAA in all three parts firstly decreased and then increased with the progress of growth period, while ZT was continuously increased. ABA content with swollen buds and horizontal roots followed an N-type trend (up-down-up). 4) GA₃ was significantly positively correlated with branching number, as was ABA with amplitude, and bundle number; their correlation coefficients were 0.942, 0.899, and 0.813, respectively. This study is helpful to ascertain the characteristics of rhizome traits of the Caucasian clover, which gives a foundation for elucidation of the regulation mechanism of hormones and the occurrence of specific rhizome characteristics.