The resulting introgression line resembled P. axillaris but produced only one-third of the nectar volume.
Researcher Martha Weiss compared the nectar volume, condition of the stigma (female receptacle of the flower), and pollen availability of pre- and postchange flowers and found that prechange flowers offered nectar rewards and were sexually viable, while postchange flowers did not offer nectar, lacked pollen, and appeared nonreceptive (Weiss 1991).
If the new food source has more nectar volume than the previous one, the bee will remember the new location and forget the old location information.
By comparing different environments we observed that nectar volume and concentration at the nectary and flower level were plastic traits sensitive to external conditions, emphasizing responsiveness to environmental changes and a consequent plasticity in nectar traits such as sugar concentration and volume.
An employed bee generates the modification of location (solution) in its memory according to local information (visual information) and tests the nectar volume (fitness value) of a new food source (new solution).
The location of a food source represents a possible optimization solution, and the nectar volume of a food source corresponds to the quality (fitness) of relevant solution, calculated by Eq. (4): {mathrm{fit}}_i=frac{1}{1+{f}_i} (4).
The concentration of floral nectar was measured immediately after collection using a temperature compensated refractometer (ATAGO N-10E refractometer, Leo Kübler GmbH, Karlsruhe, Germany) and the nectar volume was quantified using 5 µl micro-capillaries as described in [33].
Variability in nectar secretion by environmental and physiological factors [7] and the dynamic regulation of nectar volume by reabsorption [8] and refilling of nectaries upon removal [9] have been reported [3].
Using the same values in the efficiency model as used by Hodges to calculate net rate produces a critical nectar volume of 0.19 µl.
For statistics, the average nectar volume or nectar sugar concentration of all measured flowers of a plant was used.
