Application BL with seed soaking and culture media, and its effect on nodule formation and development in soybean (Glycine max L. Merr.) through influencing sugar accumulation.

摘要

Brassinolide (BL) is the most bioactive form in plant steroids, and has biological effects on many processes in plant kingdom. Currently, our understanding of BL associated with nodulation in soybean is limited. To assess the role of brassinolide (BL) in nodule formation and development of soybean, a protocol was designed based on 10 nM BL application to soybean cultured with nutrient solution. Two application methods, seed soaking defined as BL1 and addition to culture media as BL2, were used in the experiment. At 5 weeks after BL treatment, soybeans were sampled. Although nodule number was increased by BL treatment compared to control, this effect differed between seed soaking and addition to culture media. For seed soaking treatment, the increase of nodule was due to improve the taproot length and average root diameter to provide more opportunity for rhizobia infection to form nodule. Correspondingly, the nodule number per taproot length of addition BL to culture media was significantly higher (57.4%) than that of seed soaking. Not only addition BL to culture media significantly increased nodule biomass per plant, but had similar nodule size compared to control. This maybe due to much more sugar transported to nodules, and promoted nodule development compared to control. In reverse, the total soluble sugar and sucrose in roots and nodules of seed soaking treatment were less than that of control. These results suggested that both long-term and short-term BL treatment induced nodule formation in soybean, but only long-term BL treatment can improve nodule development through enhancing sugar accumulation.