Morphology and Sexual Reproduction

The soybean plant is a branched, non-frost-tolerant annual about one meter above ground level and two meters below ground level. The stem tissues are mostly primary, although the basal and more mature portions of the stems develop secondary vascular tissues during later development. This woody development is in accord with the derivation of soybean from tree ancestors in the rosewood tribe, Dalbergieae. The nodulated root system is intermediate between a taproot type and a diffuse type. The foliage leaves are alternate, pinnately trifoliolate, with pulvini, stipels, and stipules.

The soybean flower is a standard papilionaceous flower with calyx of five united sepals; zygo-morphic corolla of carina, alae, and vexillum; androecium of ten diadelphous 9+1 stamens; and gynoecium of a single carpel. Two to four seeds develop in the pods. The seeds have two large cotyledons and scant endosperm.

The anthers mature in the bud and shed their pollen directly onto the stigma of the same flower, thus ensuring a high degree of self-pollination. Cross-pollination is less than 1%, often substantially so. Soybean plants are thus virtually pure breeding homozygous lines, although manual cross-pollination is practiced routinely in breeding programs.

0 0

Post a comment