Soybean and Bees

is the main characteristic of the nectar, but some of its compounds are known to protect
against microbial attack or against insects eating the developing fruit and its included seeds
(Carter et al., 1999; Carter and Thornburg, 2000; Thornburg et al., 2003).
Homer et al. (2003) mention three stages of soybean nectary development: preactive, active,
and postactive. During both preactive and active stages, nectaries are composed of a
single-layered epidermis, containing many open stomata, with guard cells having thickened
walls, starch-engorged plastids, and other organelles. During the active and postactive stages,
additional crystals of various types (prismatic, needle-like clusters, and cubical) are found
within some of the nectary cells, in intercellular spaces, and on the outside surface near the
base of the collapsed nectary. The composition of these crystals is not known. The receptacle
calcium oxalate crystals do not disappear during nectary development and degeneration
(HORNER et al., 2000; ILARSLAN et al., 1997; 2001).
Horner et al. (2003) presented a detailed description of the three stages of nectary development
on soybeans, associated to the soybean flower (as shown on Figure 23), which are described
below.
Photos: Decio Luiz Gazzoni
A B C
Figure 23. External view of the soybean flower, according to the stages of nectary development. A) Pre-active;
B) Active; C) Post-active.
Preactive stage
During this stage, the nectary is formed between the bases of the stamen ring and the gynoecium.
At the very beginning of the preactive nectary stage, there are no trichomes on
the young gynoecium. Thin-walled, single-cell, elongated non-glandular trichomes develop
soon after, followed by two- to three-celled, elongate trichomes with very thick walls, and
then short five- to seven-celled glandular trichomes. In addition, early in nectary development,
small globular bodies appear in the space between the young nectary and the gynoe-
78 SoybeAn and bees