SOYBEAN and BEES

Häusermann, 1960) and its presence can be identified only when nectar appears on the
plant surface, or they can form anatomically distinct and sometimes highly conspicuous
structures with a complex ultrastructure (Heil, 2011).
Nectaries can be connected to the phloem, the xylem, both or have no direct vascular connection,
as stated by Fahn (1988) and Wist and Davis (2006). The nectar exits through modified
stomata that remain permanently open or through specialized trichomes (Fahn, 1988;
Wist and Davis, 2006; Vassyliev, 2010; FRANCESCHI and GIAQUINTA, 1983). Such differences
can even occur within the same plant and functional types of nectaries. For example,
stipular extra-floral nectaries of cowpea (Vigna unguiculata) form an area of widely spaced
secretory trichomes that lacks any direct connection to the vascular system, according to
Kuo and Pate (1985). They also mention that extra floral nectaries on the inflorescence stalk
consist of a region with secretory, cone-shaped tissues that are connected to the phloem and
release EFN through permanent1y open stomata.
The nectary and glandular trichome secretions may be spatially and functionally timed and,
therefore, may jointly contribute to the final nectar composition. Broersma et al. (1972), Levin
(1973) and Rivera (1996) refers glandular floral and vegetative trichomes present on some
species, which could be sites of production of anti- microbial compounds.
Soybean nectaries and production of nectar
In recent years, several studies targeted to elucidate the development and the functional
features of nectaries (Durkee et al., 1981; Durkee, 1983; Dafni et al., 1988; Fahn, 1988;
Beardsell et al., 1989; Figueiredo and Pais, 1992; Zer and Fahn, 1992; Rabinowitch et
al., 1993; Belmonte et al., 1994; Stpiczynska, 1995; Nepi et al., 1996; O’Brien et al., 1996;
Gaffal et al., 1998). While some investigation focus on the mature stage when nectar is present
or on the whole composition of the nectar (Percival, 1961; Baker and Baker, 1981;
Rabinowitch et al., 1993; Ecroyd et al., 1995; Davis, 1997; Carter et al., 1999; Carter and
Thornburg, 2000; Thornburg et al., 2003), others concentrate on nectar sugars content,
like glucose, fructose, and sucrose, largely responsible for its functionality and characteristics
(Butler et al., 1972; Baker and Baker, 1981; Roshchina and Roshchina, 1993).
In spite that the family Fabaceae comprises several cultivated plants of economic importance,
there have been relatively few (Ancibor, 1969; Waddle and Lersten, 1973; Gulyás
and Kincsek, 1982) studies dealing with the development, anatomy, and ultrastructure of
76 SoybeAn and bees