Question

Roots of plants grow towards light. Is it true or false?

Answer 1

Hint: Nearly all plants can photosynthesize, and photosynthesis is the key leading to survival of these plants. It allows them to make sugar molecules that serve the purpose of fuel and building materials. But sometimes plants respond to light i.e. to specific wavelengths of light and in other ways as well. These non-photosynthesis-related responses allow the plants to adjust in their environment and optimize growth.

Complete answer:
Proteins known as phototropins are the main photoreceptors responsible for the light detection during phototropism. The name itself reminds of their role! Like the other plant photoreceptors, phototropins are made up of a protein which is bound to a light-absorbing organic molecule, known as the chromophore. Phototropins absorb the light in the blue range of the light spectrum. When they absorb light, they change their shape, and become active, and can determine change the activity of other proteins in the cell.
When a coleoptile is further exposed to a source of light, mainly sunlight, these phototropin molecules on the illuminated side absorb a lot of light, while the molecules on the shady side absorb very much less. Such different levels of phototropin activation leads to a plant hormone known as auxin to be transported unequally down to the two sides of the coleoptile.

Hence, the correct answer is True.

Note:
Auxin causes cell elongation, causing the plant to grow more on the shady region and bend in the direction of the light source. Phototropism is a phenomenon causing directional response which allows plants to grow towards, or in some cases away from, a source of light.