Video Transcript
The graph provided shows the length increase in cells on the shaded and illuminated sides of a plant stem over time. Which group of hormones are responsible for increasing the cell length on the shaded side of the plant stem?
Hormones are chemical messengers that travel around an organism to their target cells or tissues where they cause an effect, usually in response to a stimulus. There are several hormones in plants that have different roles. Let’s take a look at some of them. Abscisic acid, also known as ABA, is a plant hormone that maintains dormancy in seeds. ABA helps seeds to survive drying out and cold weather by controlling water uptake in the seed’s embryo tissues.
Another important hormone group that plays a role in seeds is gibberellins. Gibberellins, also known as gibberellic acid, break seed dormancy and stimulate germination by allowing the uptake of water into the seed. Seed germination is the process by which a seed begins to grow when environmental conditions become suitable for the plant. Gibberellins also regulate various other developmental processes, such as stem elongation and flower development.
Auxins are a third group of hormones found in plants. Auxins are usually produced by cells in the tips of plant shoots and roots. Auxins have several roles within a plant. They are, for example, involved in cell elongation and tropisms. A tropism is a directional growth response that occurs when a plant grows toward or away from a stimulus, such as light. Growth toward or away from light is known as phototropism. When a plant grows toward light, auxins accumulate on the shaded side of the shoot and stimulate cell elongation, causing the shoot to bend in the direction of light.
So the group of hormones that are responsible for increasing the cell length on the shaded side of the plant stem are auxins.
