The final characteristics of a soybean plant are variable, with factors such as genetics, soil quality, and climate affecting its form; however, fully mature soybean plants are generally between 51–127 cm (20–50 in) in height Soybeans form inconspicuous, self-fertile flowers which are borne in the axil of the leaf and are white, pink or purple.
Like many legumes, soybeans can fix atmospheric nitrogen, due to the presence of symbiotic bacteria from the Rhizobia group.
Together, protein and soybean oil content account for 56% of dry soybeans by weight (36% protein and 20% fat, table).
Most soy protein is a relatively heat-stable storage protein.
This heat stability enables soy food products requiring high temperature cooking, such as tofu, soy milk and textured vegetable protein (soy flour) to be made.
When naming the genus, Linnaeus observed that one of the species within the genus had a sweet root. The first photosynthetic structures, the cotyledons, develop from the hypocotyl, the first plant structure to emerge from the soil.
Based on the sweetness, the Greek word for sweet, glykós, was Latinized. These cotyledons both act as leaves and as a source of nutrients for the immature plant, providing the seedling nutrition for its first 7 to 10 days.Strains that continue nodal development after flowering are termed "indeterminates" and are best suited to climates with longer growing seasons.The fruit is a hairy pod that grows in clusters of three to five, each pod is 3–8 cm (1.2–3.1 in) long and usually contains two to four (rarely more) seeds 5–11 mm in diameter.If rhizobia are present, root nodulation begins by the time the third node appears.Nodulation typically continues for 8 weeks before the symbiotic infection process stabilizes.The remainder consists of 30% carbohydrates, 9% water and 5% ash (table).