Simple Science Fair Projects
...Tropism In Plants

You can do some interesting but simple science fair projects by learning a little about a process called "tropism" in plants. A tropism is a plant's response to a stimulus in its environment. The response is an increased growth in part of the plant causing a turning movement or bending of that part of the plant.

Types Of Plant Tropisms

Most of the time the stem of a plant will show positive phototropism and grow towards the source of light. Roots though usually show a negative phototropism and grow away from the light.

Plants have photo receptors that can sense different wavelengths of light. Blue light for example can cause a positive phototropic reaction in plant stems and a negative reaction in roots. But red light will usually cause a positive reaction in both roots and and stems causing them to grow towards that light.

You may be getting some ideas already about some simple science fair projects you could put together on this aspect of plant tropism.

Gravitropism- Gravity is the stimulus here. Cellular growth is more on the tops of root tips than on the under sides. This causes the roots to grow down towards the pull of gravity. Stems on the other hand grow in the opposite direction and away from the pull of gravity.

Hydrotropism- Water is the stimulus for this plant tropism. Roots will tend to bend and grow towards the highest concentration of water around them.

Positive thigmotropism- Cells elongate more on the stem side not touching and object and less on the opposite side. This causes shoot growth to coil around an object like a vine does.

Negative thigmotropism- Elongation of cells is greater on the side of a stem that is touching something than on the other side. Thus the plant grows away from the object its touching.

This type of plant tropism could certainly be easily developed into some simple science fair projects and with very little supplies too.