Plant Reproduction, Fertilisation and Pollination (Worksheet 4)
Carpel is the name given to the female parts of the flower. These are the stigma, the style and the ovary. Stamen is the name given to the male parts of the flower. These are the anther, the pollen grains and the filament.
The anther produces pollen grains, which are the male sex cell. These pollen grains (through pollination) will land on the stigma of a flower and grow a pollen tube through the style to the ovule (the female sex cell) within the ovary.
Once the pollen tube reaches the ovule, a nucleus of the
male cell can fuse with a nucleus in the female cell allowing fertilisation to
occur. Then the ovary turns into a fruit and the ovule will grow into a seed.
The way in which a pollen grain is transferred to a stigma is called
Pollination. It is interesting to note that plants can either self-pollinate
(pollen grain transfers to the stigma of the same plant) or cross-pollinate
(pollen grain transfer to stigma of another plant).
When cross-pollination occurs the pollen grain must
obviously be moved to another area where it can attach itself to a stigma.
Cross-pollination occurs in two ways - either by wind or by insects.
In order to attract insects to carry the pollen grains away, flowers normally
have bright coloured petals to draw the insects in. The pollen grains are sticky
and stick to the legs of insects that then carry the grains away where they will
attach to the stigma (which is also sticky). Flowers that depend on insect
pollination have other ways of attracting insects such as scented flowers or
sugary nectar.
Flowers that are dependent on wind pollination have no need to attract insects.
Hence the petals on these flowers tend to be not so brightly coloured and
generally have no scent or nectar. However in order to have the best possible
chance of pollination, these plants will tend to have long filaments which allow
the anther to hang outside of the flower so that the wind can catch and carry
the pollen grains to a stigma.
Answer the following:
| 1. | What name is given to the
female parts of the flower? |
| 2. | What are the three elements
of the female part of the flower? |
| 3. | What name is given to the
male parts of the flower? |
| 4. | What are the three elements
of the male part of the flower? |
| 5. | What part of the flower
produces the pollen grains? |
| 6. | To what part of the flower
must pollen grains be attached to for fertilisation to occur? |
| 7. | What is the male sex cell? |
| 8. | What is the female sex cell? |
| 9. | What is self-pollination? |
| 10. | What are the two ways in
which cross-pollination can occur? |
| 11. | Name three characteristics
of a flower that uses insect pollination. |
| 12. | Name one typical
characteristic of a flower that uses wind pollination. |