It is believed that a yellow pigment related to riboflavin acts as a photoreceptor for light.
a. Following reception, plant hormone auxin migrates from bright side to shady side of a stem.
b. How reception of stimulus couples to production of auxin is not yet known.
4. Auxin is also involved in gravitropism, apical dominance, and root and seed development.
Phototropism is the growth or movement of plants in response to light. Plants use specialized cells called photoreceptors to detect light and then produce hormones that cause uneven growth, resulting in the plant bending towards the light source.
The two main types of photoreceptors involved in a plant's light response are blue-light photoreceptors and red/far-red light photoreceptors. Blue-light photoreceptors help plants sense the direction and intensity of light, while red/far-red light photoreceptors help regulate the plant's growth and development.
Plants use a process called phototropism to determine the direction of light. They do this by comparing the amount of light received by different parts of the plant, and then producing hormones that cause the plant to grow more on the shaded side, resulting in the plant bending towards the light source.
Aside from light, other environmental factors that can affect a plant's light response include temperature, humidity, and the presence of other plants. For example, high temperatures can inhibit a plant's growth towards light, and the presence of other plants can cause competition for light, resulting in altered growth patterns.
No, not all plants exhibit positive phototropism towards light. Some plants, like those in the pea family, exhibit negative phototropism, where they grow away from the light. This is because they have evolved to grow towards the darkness to avoid competition for light with other plants.