Experimental Setup of Phototropism

Introduction to Experimental Setup of Phototropism

Light is responsible for various plant responses and physiological processes. Phototropism is the growth response of a certain plant to the direction of the light. A simple experiment can demonstrate this effect by growing potted plants in two different conditions: plants in pot A are put near a window, while plants in pot B are exposed to open sunlight. After a week, the plants near the window exhibit bending of the shoot tips in the direction of the light source, whereas the shoot tips in the other setup do not bend. Auxin is the plant hormone responsible for the plant’s movement in the direction of light.

Experiment Description

Pea and mustard plants are commonly used to demonstrate phototropism because their stems are more flexible than those of shrubs, making it simpler to observe the bending of the stem towards the light source.

In this virtual experiment, Pot A and Pot B, two potted healthy pea plants, were positioned next to a window and in direct sunlight. The plants in both conditions were watered on a regular basis to ensure optimal growth and were observed for 5 days.

Initially, no visible stem curvature was noticed in either experimental pots, but on day 5, significant stem curvature towards the light source was observed in pot A, which was put near the window, demonstrating light-induced plant movements known as phototropism.

Auxin, a plant hormone that stimulates cell elongation, causes shoots in pot A to bend towards a light source due to its concentration on the shadowed side. Plants in pot B did not bend their shoots even after five days due to the uniform distribution of auxin molecules in open sunlight.

Similar results were found for mustard plants also, indicating that when plants are exposed to a unidirectional light source, the shoots bend towards the light source, demonstrating plant phototropism.

FAQs on Experimental Setup of Phototropism

Q1.Define plant phototropism.

Ans. Phototropism is the growth response of a certain plant to the direction of the light.

Q2. Explain the role of auxin in plant phototropism.

Ans. Plant phototropism is caused by auxin, a plant hormone that promotes cell elongation. When plants are exposed to a unidirectional light source, auxin concentration is higher on the shaded side of the plant than on the light-exposed side. The enhanced cell elongation and growth caused by the differential concentration of the auxin hormone causes the shoot to bend towards the light source.

Q3. Why do the plants exposed to open sunlight not exhibit bending of shoots?

Ans. In open sunlight, all regions of the plant shoot are equally exposed, resulting in an even distribution of auxin hormones and no bending of the shoot.

Q4. Why herbaceous plants are recommended to study plant phototropism?

Ans. Herbaceous plants are used to demonstrate phototropism because their stems are more flexible than shrubs, making it easier to detect the bending of the stem towards the light source.

Q5. Explain the advantages to plants that exhibit positive phototropism.

Ans. Phototropism allows plants to develop faster and more efficiently by allowing them to reach areas of higher light intensity. It assists plants in orienting themselves in the direction of the sun, helping them to get the most out of their exposure to sunlight. Phototropism allows plants to avoid places of high wind, which can damage their leaves and branches.