SOYBEAN and BEES

Photos: Decio Luiz Gazzoni
A
B
Figure 11. Soybean flowering: axillary and terminal inflorescence. A) Inflorescence in the axil of soybean; B)
Terminal inflorescence.
Structure of a soybean flower
Soybean produces a typical papilionaceous flower, with a tubular calix of five unequal sepal
lobes, and a five-parted corolla, consisting of a) one posterior banner petal; b) two lateral
wing petals; and c) two anterior keel petals in contact with each other but not fused.
When a bud in the axil of a trifoliolate leaf develops into an inflorescence, the stalk of that
inflorescence remains stem-like, with typical stem anatomy, including epidermis, cortex,
endodermis, vascular tissue, and considerable secondary growth from a vascular cambium
(Dzikowski, 1937). In the development of an inflorescence, the bract of each flower is homologous
to a trifoliolate leaf, and the two bracteoles are homologous to the prophylls that
normally develop at the base of every branch. After forming the primordia of the bracteoles,
the apical meristem of the flower gives rise directly to the floral organs.
The 10 stamens collectively called the androecium occur in two groups, in which the filaments
of nine of the stamens are fused and elevated as a single structure, whereas the posterior
remains separate.
The single pistil is unicarpellate and has one to four campylotropous ovules alternating
along the posterior suture (Carlson and Lester, 1987). The style is about half the length of
the ovary and curves backward toward the free posterior stamen, terminating in a capitate
stigma. Figures 12 and 13 show examples of flowers of the soybean family (Fabaceae), identifying
its parts. Figure 14 shows a top transversal view of structures of the soybean flower
and Figure 15 shows a schematic longitudinal view of a soybean flower.
SoybeAn and bees
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