Pollination (continued)
Water pollination
Although the pollen grains of some plants can be made to
germinate in aqueous sugar solutions, water alone in most
cases will destroy them. Accordingly, water is seldom the true
medium of pollen dispersal, even in aquatic plants. In ribbon
weed (Vallisneria), the male and female flowers are released to
the surface separately. At the surface, male flowers are driven
by the wind until they bump into female flowers; the shock
causes the pollen to be catapulted over to the stigma. True
water dispersal of pollen (hydrophily), in which the grains are
wetted, is found only in the freshwater hornworts (Ceratophyl-
lum) and marine seagrasses (Zostera and Phyllospadix).
Ecology
Traditionally, pollination biology has considered mechanisms
that promote or guarantee the proper transfer of pollen from
one individual of a given plant species to another. Often this
involves a careful description of the transfer mechanism
coupled to a particular pollinating agent (such as hawkmoths,
bumblebees, bats, or wind). Pollinator-plant interactions,
however, have also been used as a model for understanding
broader evolutionary and ecological issues that pertain to all
living systems. Pollination systems have proven to be an excel-
lent model for studying many issues in population biology. In
addition, because plants have a variety of breeding structures,
they provide an opportunity for assessing the reproductive
value of different sexual strategies and for modeling the evolu-
tion of breeding systems. Moreover, if pollen movement is
considered as a measurable analog of gene movement, then
pollination systems are ideal for unraveling patterns of gene
flow and the concomitant genetic structuring of plant popula-
tions. Overall, the evolutionary ecology of many plants and pol-
linators may be best understood as a result of complex interac-
tions among populations of many species.
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