Integrated Science

Grade: 10 (2)

Topic: Sexual Reproduction in Plants

Sub Topic: Pollination

Pollination is the process that facilitates sexual reproduction in plants. It involves the transfer of pollen grains (male sex cells) from the anther to the stigma of the female reproductive organ. Once the male and female sex cells come in contact they fuse fertilisation occurs.

Since the male and female reproductive structures are separate, pollination can occur in two ways:

1 self-pollination

2 cross-pollination

Self-pollination occurs when the pollen grains are deposited on the stigma of the same flower or of a different flower on the same plant.

Cross-pollination occurs when the pollen grains are transferred from the anther of one flower to the stigma of a different flower.

Advantages of cross-pollination

1. Greater variety of offspring2. Offspring are usually stronger less susceptible to disease3. Increases the chance of successful reproduction4. Increase the chance of a new favourable traits developing5. Increase yield and quality

Agents of pollination

When the anther matures it splits open, releasing the pollen grains. The pollen grains are unable to move to the stigma of a flower on their own; therefore, they require the assistance from an external agent known as pollinators or agents of pollination. Wind, insects and other animals are agents of pollination. The table below outlines and compares the characteristics of the wind-pollinated and insect-pollinated flower.

Insect pollination

Insect often enter flowers in search of nectar. As the insect (or animal) brushes past the stamens, to enter into the flower, the pollen grains stick on its body. On visiting another flower the pollen is then brushed onto the surface of the stigma.

Wind pollination

The structure of wind-pollinated flowers is quite different from that of insect pollinated flowers, as noted in the table above. The petals of wind pollinated flowers are usually very reduced or inconspicuous. However, the stamens are feathery and are very long so that the anthers hang outside the flower into the wind. The pollen grains are made in very large quantities to improve the chances that some are successfully caught on the feathery stigma of another flower of the same species.

Insect pollination Wind pollination

Activity

Instruction: answer all the following questions.

1. What is pollination?2. Explain the difference between self and cross-pollination.3. What are agents of pollination?4. Give two examples of wind-pollinated flowers.5. State the differences between a wind-pollinated and an insect pollinated

flower.6. What type of pollinating agent would help to pollinate a flower that has a

smooth pollen and a feathery stigma?7. Why do wind-pollinated flowers produce large amount of pollen grains?

8. Is this flower wind or insect-pollinated?

9. How do the pollen grains becomes attached to the body of an insect?10.Why are the stamens of wind-pollinated flowers long and feathery?