WATER-SOLUBLE CARBOHYDRATE ACCUMULATION IN SOYBEAN PLANTS

Soybean [Glycine max (L.) Merrill] plant samples from field fertility experiments on Webster soil (Typic Halplaquoll) were collected and analyzed during 2 growing seasons to study the effect of different variables on WSC [water-soluble carbohydrate] contents of different plant parts at various stages of plant development. WSC in dried plant samples were extracted with hot water and determined using a phenol-colorimetric method with glucose as a standard. The WSC content of leaves and petioles increased at 9 a.m.-1p.m. daily. WSC contents generally were higher in 1971 than in 1972. Differences in WSC among cultivars and fertility levels were relatively small. Percentages of WSC in leaves increased throughout the growing season, but in stems and petioles increased only until seed development became rapid. WSC contents of stems, petioles and pods decreased as the seeds developed. This decrease may indicate that soluble CHO (metabolically active carbohydrate) becomes a limiting factor for seed production during the seed-filling period.