Soybean and Bees

The volume of nectar on each flower varied significantly between soybean cultivars (0.2
to 0.5 μL), also increasing with warmer temperatures, as observed by Sverson and Erikson
Junior (1984). When soybean flowers were compared as two distinct groups, there were no
apparent differences in nectar characteristics among white-flowered and purple-flowered
cultivars. Time of the day was the primary factor affecting soybean nectar characteristics;
nectar fructose, glucose, sucrose, and total carbohydrate content increased with time of day,
while the volume of nectar per flower decreased. Day-to-day and temperature effects on
nectar characteristics were minimal. Comparisons made within individual sampling periods
suggest that there are differences in nectar characteristics among cultivars, which could
encourage preferential foraging by honeybees.
Flower, pods and seeds abscission on soybeans
Several investigators have reported that a soybean plant produces many more flowers than
can develop into pods. From 20 to 80% of’ the flowers are subjected to abscise depending
on the genetic and environmental conditions (Dall’Agnol, 1980 ; Hansen; Shibles, 1978;
Hardman, 1970; Van Schaik; Probst, 1958; Wiebold et al., 1981). Most cultivars with
many flowers per node have a higher percentage of flower abscission than those with few
flowers per node (ANDREWS, 1966).
Abscission is not restricted to flower and can happen from the triggering of flower development
to the pods. Abscission can occur at the time of bud initiation, during the development of
floral organs, at the time of fertilization, during the early proembryo stage, or at any stage of
cotyledon development (WEBSTER and LEOPOLD, 1977). Flower abscission occurs most often
from 1 to 7 days after the start of flowering (stage R1) (Kato and Sakaguchi, 1954; Kato
et al., 1955; Pamplin, 1963; Williams, 1950), and pod abscission after flowering (Carlson
and Lersten, 1987). Normally, the earliest and latest flowers are more often abscised, but
even after pod set, some of the seeds or even entire pods can be aborted (Zhang; Smith,
1999).
Apparently, the plant produce more flower than the photosynthates reserves can support if
thoroughly developed into pods and seeds, and a continuous balance is ongoing to fine-tune
the plant capacity to generate the maximum amount of viable seeds to perpetuate the species.
There are no reports of insects pests responsible for soybean flower abscission larger
than the natural process normally produces. This hypothesis is much in line with the wellknown
soybean resilience to insect pests attacks and damages, even along the reproductive
48 SoybeAn and bees