The physiological basis for cytokinin induced increases in pod set in IX93-100 soybeans

• Published in: Plant physiology (Bethesda) 1987-06, Vol.84 (2), p.233-239
• Main Authors: Carlson, D.R, Dyer, D.J, Cotterman, C.D, Durley, R.C
• Format: Article
• Language: English
• Subjects: 6-BENZILADENINA; 6-BENZYLADENINE; ABSCISION; ABSCISSION; Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical agents; CITOCININAS; CYTOKININE; CYTOKININS; Development and Growth Regulation; Economic plant physiology; FLORA; FLORACION; FLOWERING; Flowers; Fructification, ripening. Postharvest physiology; FRUIT; FRUTO; Fundamental and applied biological sciences. Psychology; GLYCINE MAX; Growth and development; Inflorescences; PESO; Plant physiology and development; Plants; POIDS; PRO0595DUCTION DE SEMENCES; PRODUCCION DE SEMILLAS; Root pressure; SEED; SEED PRODUCTION; Seed weight; Seeds; SEMENCE; SEMILLAS; Soybeans; Vegetative apparatus, growth and morphogenesis. Senescence; WEIGHT
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.84.2.233

Previous investigations have shown the feasibility of increasing pod number on legumes by the application of 6-benzylaminopurine (BA) directly to the raceme. These investigations were designed to determine what reproductive parameter was affected by cytokinin application, and if these applications were overcoming a deficiency in root-produced cytokinins during late flowering. Five individual main stem racemes on greenhouse grown soybeans (Glycine max L. Merr.) were treated with 2 millimolar BA. A single application of BA when pods appeared at 25 to 50% of the proximal floral positions resulted in a 58% increase in pod set due primarily to a 33% reduction in floral abscission. Applications of BA at later intervals also resulted in significant reductions in total abscission. When three applications of BA were imposed on the upper five nodes of field grown soybeans, total pod number and seed weight were significantly increased in this section of the canopy by 27 and 18%, respectively. Throughout the flowering period, root pressure exudate was sampled for the subsequent separation and quantification of zeatin, dihydrozeatin, zeatin riboside, dihydrozeatin riboside, and isopentenyladenine. Total cytokinin flux peaked from 0 to 9 days after flowering began, and then dropped to one-half of this level by 15 days postanthesis. The probability that a flower would initiate a pod was directly related to the concentration of total cytokinins present in the exudate when the flower opened.