Abstract: Higher tiller than stem is one of the important factors that hinder the uniformity and mechanical production of Sorghum bicolor. Endogenous hormones and their interaction effects play a key role in plant height building. To further explore the effects of endogenous hormones on height difference between stem and tiller of sorghum, Sorghum K35-Y5 with the same height of stem and tiller and 1383 with higher tiller than stem were used to measure the plant height and endogenous hormone contents in main stem booting stage, tiller booting stage, main stem flowering stage and tiller flowering stage, and analyze the dynamic change and correlation. The difference of height of stem and tiller in different stages showed that the stem of K35-Y5 was higher than that of tiller in the first three periods, and the height of[1] stem and tiller was basically the same at tiller flowering stage. The stem height of 1383 was higher than that of tiller in main stem booting stage, the height of stem and tiller was basically the same in tiller booting stage, and the height of tiller was higher than that of stem in the latter two stages. The analysis of dynamic change of endogenous hormone in different stages showed that GA₃ content in stem and tiller was basically consistent with the change of plant height. The dynamic change of ABA in K35-Y5 stem and tiller is basically the same, was significantly higher than stem of 1383 tiller in main stem flowering stage. The contents of IAA, ICA, tZR, IPA, Dx and JA showed a decreasing trend. ACC, SA, JA and H₂JA had no obvious characteristics. The correlation analysis showed that the difference of tiller and stem was positively correlated with the relative content of GA₃ at tiller booting stage, main stem flowering stage and tiller flowering stage, and positively correlated with the relative ratio of GA₃/ABA at main stem flowering stage and tiller flowering stage. Above of all, the height difference of stem and tiller was closely related to the relative content of GA₃ at tiller booting stage, main stem flowering stage and tiller flowering stage. Through the treatment of GA₃ and paraffin section, we found that spraying GA₃ affects cell elongation to achieve the improvement of plant height uniformity. This will be of great significance for the breeding of sorghum varieties suitable for mechanized production.

Key words: Sorghum bicolor, main stem, tiller, heigh difference, endogenous hormones