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 6 nectaries DHJanzen101021.jpg high resolution
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It is very common for the reward to pollinators (and to visitors as well, though they are thieves) to be nectar produced by glands (a.k.a. floral nectaries) inside the flower at its base. You have already met extrafloral nectaries on the petioles of ant-acacia leaves. They also occur on developing fruits and on the outsides of flowers - not to attract pollinators, but to attract ants, ants that end up protecting the plant part as they possessively patrol the nectary or simply as they forage at it. This African ant is visiting extrafloral nectaries on immature fruits. Floral nectar is chemically complex, and may contain many different kinds of sugars and amino acids (among other things). This comment will be revisited below, but for the moment, suffice to say that selection has operated to generate different rewards for different sorts of pollinators. Equally as part of attracting certain pollinators and not attracting other pollinators/visitors, nectar is produced at distinctive times of day and at distinctive times in the cycle of opening-to-withering of the flower. |
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