Soybean and Bees

(Severson, 1983). He observed that white flowered varieties had a more uniform
carbohydrate content per flower throughout the day than did purple flowered varieties.
There were no significant differences in total carbohydrate content but fructose and
glucose content in white flowered varieties varied significantly with day, time, and
temperature while sucrose content of purple flowered varieties varied significantly with
time.
Severson (1983) examined nectar characteristics of soybean cvs. Centennial and Coker 237
grown in Marion, AR, during 1980 and 1981. Nectar secretion decreased with time and increased
with temperature, while fructose, glucose, sucrose, and total carbohydrate content
and carbohydrate per flower increased with time and temperature. He also observed that
environmental factors promoting plant stress appear to influence nectar carbohydrate composition
as water deficiency promoted a decrease in sucrose content and a 4-fold increase in
fructose and glucose content.
Severson (1983) also analyzed soybean cvs. Bragg, Centennial, Coker 237, and Davis for
honeybee attractiveness in cage studies. He found out that honeybee foraging was nonrandom
as individual bees exhibited greater varietal fidelity to ‘Centennial’ and ‘Davis’ than to ‘Bragg’
and ‘Coker 237’. Attractiveness to honeybees was not correlated with nectar characteristics
as ‘Coker 237’ and ‘Bragg’ appeared to produce a more highly attractive nectar (i.e. nectar
quantity and quality) than ‘Centennial’ or ‘Davis’. Initial honeybee attraction to soybean
flowers is theorized to be determined by floral volatile components with ‘Centennial’ and
‘Davis’ producing a more attractive volatile spectrum (i.e. quantity and/or quality) than the
cultivars Bragg or Coker 237.
Soybean flowers have a period of viability for pollination and fecundation, which regulates
bee foraging, highly related to the availability of pollen and nectar (monsi, 1942). According
to Free and Williams (1973), the sugar concentration of nectar in the flowers determines the
frequency of visitors, while the volume determines the quantity of honeybee foragers that
will visit. Under Brazilian conditions, the visit of honeybees to soybean flowers normally occurs
between 9:00h and 15:00h every day. The peak of these activities and the time in which
the flowers will remain open vary between the cultivar and the local environmental condition.
The contents of total sugar in nectar varied from 37 to 45%, and the sugar of soybean flowers
increased and the volume decreased according to the time of the day and temperature
(Erickson, 1984; Delaplane and Mayer, 2000). The intensity of foraging by honeybees is
linked to the nectar volume and nutritional characteristics (Heinrich, 1979; Hagler, 1990)
and particularly to the sugar profile (Waller, 1972; Abrol and Kapil, 1991; Abrol, 2012;
BIELESKI and REDGWELL, 1980; BREWER et al., 1974).
SoybeAn and bees
47