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Title: THE INFLUENCE OF ROOT APPLIED BRASSINOSTEROIDS AND CARBENOXOLONE ON GROWTH AND NODULATION OF SOYBEAN (GLYCINE MAX. L.) SEEDLINGS.

Author
item Hunter, William
item BAKER, M - UNIV. OF CA/ SAN DIEGO CA

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2000
Publication Date: 12/21/2000
Citation: Hunter, W.J., Baker, M.E. 2000. The influence of root applied brassinosteroids and carbenoxolone on growth and nodulation of soybean (Glycine max. l.) seedlings. Journal of Agronomy and Crop Science. 186(4): 217-222.

Interpretive Summary: This study examined the influence two plant-steroid hormones and an inhibitor of steroid metabolism had on the growth and nodulation of soybean plants. 24-Epibrassinolide and 28-homobrassinolide belong to the brassinosteroid family of plant steroid hormones that promote growth plant growth when applied to the stem or leaves. Carbenoxolone, an analog of glycyrrhizic acid, inhibits enzymes important in steroid and prostaglandin action in animals. We examined the effect these compounds had on root and shoot growth of Glycine max (L.) Merr. cv. Tracy M. Root application the brassinosteroids reduced total plant wet weight, root length, shoot length, first internode length and number of lateral roots. Effects were observed at concentrations as low as 0.1 uM. Nodulation was reduced by 24-epibrassinolide treatment. The effect may have been a direct one on nodulation or an indirect one resulting from the general inhibition that brassinosteroids had on root development. In the same assay, carbenoxolon reduced lateral root formation, but did not reduce nodule numbers, root length or weight, nor stem length. The influence of carbenoxolone on lateral root numbers implys the involvemnt of plant steroid hormones in their development.

Technical Abstract: 24-Epibrassinolide and 28-homobrassinolide belong to the brassinosteroid family of plant steroid hormones that promote growth. Carbenoxolone is a synthetic analog of glycyrrhizic acid which inhibits enzymes important in steroid and prostaglandin action in animals. We examined the effect these compounds had on root and shoot growth of Glycine max (L.) Merr. cv. Tracy M. Both brassinosteroids reduced total plant wet weight, root length, shoot length, first internode length and number of lateral roots. Effects were observed at concentrations as low as 0.1 uM. Nodulation was reduced by 24-epibrassinolide treatment. The effect may have been a direct one on nodulation or an indirect one resulting from the general inhibition that brassinosteroids had on root development. In the same assay, carbenoxolone reduced lateral root formation, but did not reduce nodule numbers, root length or weight, nor stem length or weight.