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Reproduction
in plants
Joanna
George-Johnson, Contributor
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| Members
of the Oberlin High School choir, winner of TVJ's 'All Together Sing' 2005, don
Jamaica's national colours as they rock the audience in TVJ's studios, on November
17, 2006. - Colin Hamilton/Freelance Photographer | One
of the fundamental characteristics of all living things is that they reproduce.
Plants are, therefore, no exception. Living
things have two main ways to reproduce, namely, asexual and sexual. Even though
it is possible to generate entire plants using asexual reproduction, especially
in farming, most plants have the ability to reproduce sexually. The advantage
to the plant is that its offspring have a selection of genes from two parents,
so each individual's genes are different. The offspring are not identical and
there is variety in the species. The
sexual organ of a plant is the flower. The flower contains both the male and female
sex structures. Some flowers have both, others have only one. A
flowering plant's sexual organs consist of: - The
stamen, or male sex structure, consisting of a filament and a pollen-bearing anther
at the tip.
- The
pistil, or female sex structure, consisting of ovary and ovule, style, and stigma
at the tip. (The pistil is also sometimes called the carpel.)
Here's
how it works: 1.
An insect or the wind carries pollen grains from the anther of another flower.
2. The
pollen grains land on the stigma and a pollen tube grows down through the style
to the ovary. 3.
The nucleus of the pollen grain passes down the tube. It fertilises the egg cell
inside the ovule. 4.
The fertilised egg cell develops into an embryo. 5.
The ovary becomes the fruit. 6.
The ovule becomes a seed - from which (once dispersed) the offspring plant will
grow. (See diagram.) 
The
function of the parts of the flower: - The
stamen (male part of flower).
- Anther
- This is found on the top of the stamen; it produces pollen.
- Pollen
- A yellow, powdery substance that contains the male gamete.
- Filament
- holds the anther upwards so it can be exposed to the elements for ease of pollination.
- The
pistil (female part of flower).
- Stigma
(top of the pistil) - Has a sticky surface that causes the pollen grains to stick
to it for pollination to occur.
- Produces
a substance that the pollen will use to make the pollen tube.
- The
ovary contains the ovules - female gametes.
Questions:
For
each of the structures of the flower, write the corresponding structure in the
human reproductive system. Give
two advantages and two disadvantages of sexual reproduction. Joanna
George-Johnson teaches at Ardenne High School.
Email: Masterbio@gmail.com.
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