Soybean and Bees

crose, fructose, and glucose; dominant fructose and glucose. It has been proposed that nectar
quantity and quality may play an important role in determining the search of foraging honeybees
(Waddington and Holden, 1979), although it is not clear whether bees alter their
foraging strategies considering the hourly and daily fluctuations in nectar characteristics of
individual species.
Frey-Wyssling (1955) supported the theory that nectar secretion is related to the phloem
supply to floral nectaries because the number of cells between phloem sieve tubes and the
surface of floral secretory tissue cannot exceed a certain amount (in most cases about ten
cells) for abundant nectar secretion to occur. However, nectar composition differs considerably
from that of phloem sap (Ziegler et al., 1959) and has been proposed by Luttge (1977)
to be a function of specific active transport mechanisms.
In this context, the primary enzyme would be the apoplastic invertase located in the tissues
surrounding the phloem unloading and that allows sucrose to non-photosynthetic organs
that follow an apoplastic pathway after the phloem, such as the reproductive organs. Ruhlman
et al. (2010) observed that the production of nectar is closely linked to the presence of
the enzyme apoplastic invertase; therefore, a greater nectar production was dependent on
an increase in enzyme activity in addition to the photosynthetic capacity of the plant itself.
These authors observed that in Arabdopsis, in the absence of genes encoding isoforms of the
enzyme, predominantly in reproductive organs, prevented the production of nectar.
Invertase promotes the hydrolysis of sucrose to the hexoses glucose and fructose and can be
located in the cell wall (apoplastic), vacuole (vacuolar) or cytoplasm (cytoplasmic). The cell
wall invertase is important when unloading the phloem follows an apoplastic path facilitating
the passage of sucrose to the drains tissues. Some studies even conclude that the importance
of apoplastic invertase is not restricted to the breakdown of the sucrose molecule, since the
injection of glucose and fructose has the same effect on the passage of photosynthates to the
phloem tissue drains. In this case, the authors attribute to the enzyme a possible broader role
as signaling or regulatory (Cheng and Chourey, 1999).
Further evidence of the importance of apoplastic invertase in phloem unloading process
that follows this path is the abundance of transcripts in these tissues (Jin et al., 2009) and its
almost non-existence in tissues with symplastic unloading (Ruan and Patrick, 1995), both
observed from tomato tissues. In Vicia faba, tissues surrounding the seed formation, which
have no connections of plasmodesmata, also show high expression of the enzyme (Weber
et al., 1996).
Honeybees collect sucrose solutions in the 30-50% range in preference to higher or lower
concentrations (Waller, 1972; Woodrow, 1968). Jamieson and Austin (1956) found that
SoybeAn and bees
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