Page 243 - Primary Six Notes

2. Geotropism

This is the growth movement of plant roots towards the direc-

tion of the force of gravity. Plant roots grow downwards due to
the force of gravity.

3. Hydrotropism

This is the growth movement of plant roots towards the

source of water or moisture

4. Thigmotropism

This is the growth movement of certain parts of some plants in

response to the stimulus which help climbing plants such as

passion fruits and beans to twine or clasp on other plants.

5. Chemotropism

This is the growth movement of plants parts towards a source

of chemicals, e.g pollen tubes grow towards the stigma,

through the style towards the ovary and finally towards the

ovules.

Summary

Tropism Stimulus

Phototropism light

Geotropism Force of gravity

Hydrotropism Water and moisture

Thigmotropism touch

Chemotropism Chemicals other than water