SOYBEAN and BEES

Illustration: Decio Luiz Gazzoni
Stigma
Filament
Style
Petal
Pollen grains
Anther
Fused stamens
Ovary
Ovule
Nectary
Calyx
Figure 15. Schematic representation of the soybean flower, including the nectary.
Before the margins of the leaf-like pistil fuse, two to four ovule primordia are produced alternately,
and develop simultaneously, on the inner surface of the margins of the placenta
(Guard, 1931; Pamplin, 1963). Each ovule becomes campylotropous, with its micropylar
end directed upward toward the stigma.
The nectary is visible, about 10 days before anthesis, as a rim of tissue between the base of
the pistil and the stamens. At the time of anthesis, the discoidal nectary is a fully formed
cup about 0.2 to 0.4 mm in height encircling the base of the staminal sheath (Carlson,
1973; Erickson; Garment, 1979).
The slightly oval nectary stomata are concentrated on each side of the adaxial indentation
of the nectary, where it contacts the filament of the free ventral stamen. Most of the stomata
are located over the rim and ventral interior surface of the nectar cup, occasionally in
groups of two or three. On the abaxial side of the cup there are only a few stomata (Waddle;
Lersten, 1973; Erickson; Garment, 1979) noted that nectaries are largely vasculated by
phloem branching from the staminal base.
Nectariferous tissue is, therefore, most closely associated with the stamens. It is not a random
structure, but deliberate associated in order to force the insects to have close contact
with the stamens to get the nectar. By the contact, the body of the pollinators is covered with
pollen, carried to the stigma of the same flower (perfect flowers) or to the female flower on
44 SoybeAn and bees