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How Does Pollination
Help In The Study Of Climates?
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Sometimes when
taking a walk in a garden during the spring season, you may have
been seized with an unexpected bout of sneezing. There could be
a reason for this. It could be the time when millions of pollen
grains are wafting along, causing sneezing and watery eyes
associated with pollen allergies.
Why are they
suddenly wafting along in clouds? For a purpose, of course.
Nature has decided that a process called pollination needs to
takes place in order that all grains, fruits, vegetables,
wild flowers and trees may produce seed or fruit. Pollination
refers to the transfer of pollen grains from the male structure
of a plant to the female structure of a plant, preparing the
plant for fertilization. |
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Well, it sounds like an
easy process. The catch is that pollen grains are microscopic in
size. They range in diameter from less than 0.01 millimeter to a
little over 0.5 millimeters. The outer covering of pollen grains,
called the pollen wall, may be intricately sculpted with designs and
these designs are used to distinguish between plant species. A
chemical in the wall, called sporopollenin, renders the wall
resistant to decay.
Plants have two methods
of pollination: cross pollination or self pollination, but some
species are capable of both. Most plants are designed for
cross-pollination, in which pollen is transferred between different
plants of the same species. Cross-pollination introduces genetic
diversity at a rate that enables a species to cope with a changing
environment. New genes ensure that at least some individuals can
endure new diseases, climate changes, or new predators, enabling the
species as a whole to survive and reproduce. Cross-pollination also
ensures that beneficial genes are transmitted relatively rapidly to
succeeding generations.
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In self-pollination,
pollen is transferred from the stamens to the pistil within one
flower. The resulting seeds and the plants they produce inherit the
genetic information of only one parent, and the new plants are
genetically identical to the parent. The advantage of
self-pollination is the assurance of seed production when no
pollinators, such as bees or birds, are present. It also sets the
stage for rapid propagation—weeds typically self-pollinate, and they
can produce an entire population from a single plant. The primary
disadvantage of self-pollination is that it results in genetic
uniformity, which makes the population vulnerable to extinction.
Another disadvantage is that beneficial genes do not spread as
rapidly as in cross-pollination, because one plant with a beneficial
gene can transmit it only to its own offspring and not to other
plants.
Can pollination help
in the study of the climate of a region?
Although the single cell inside the wall is viable, or living, for
only a few weeks, the distinctive patterns of the pollen wall can
remain intact for thousands or millions of years. In fact,
scientists track long-term climate changes by studying layers of
pollen deposited in lake beds. For example, the tanglehead grass and
vine mesquite grass thrive in a dry climate and their pollen drifts
over lakes, settling in a layer at the bottom. If a climate change
brings increased moisture, desert species are gradually replaced by
forest species such as pines and spruce, whose pollen forms a layer
on top of the grass pollen. Scientists take samples of mud from the
lake bottom and analyze the pollen in the mud to identify plant
species. Comparing the identified species with their known climate
requirements, scientists can trace climate shifts over the
millennia. |
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