Question

What are tropic movements in plants? Why does the shoot of the plant bend towards light when it is kept in a cardboard box with a small hole on one of its side?

Answer 1

• The tropic movements in plants can be defined as growth movement in response to a specific stimulus such as light, gravity, temperature, chemical substances, water, solid particles. The plants can show either positive (towards the stimulus) or negative (away from the stimulus) growth movement in response to the particular stimulus.
  
• The shoot of the plant bend towards the light when it is kept in a cardboard box with a small hole on one of its side, this happens due to phototropism.
• Phototropism is a phenomenon in which the growth of plants takes place in response to the light stimulus. Usually, plant shoots and leaves show positive phototropism whereas roots exhibit negative phototropism. Auxin plays an important role in phototropism. Depending on the direction of light stimulus plants begin redistribution of the auxin molecules to the farthest side from the light. As a result, the plant cells located distant from the sunlight contain greater auxin concentration show faster growth, which eventually causes the shoot to bend towards the light that enters through the hole of the cardboard box. This mechanism enables plants to receive more amount of light to enhance the rate of photosynthesis.