9700 · 15.2
Control and coordination in plants
Ever wondered how a plant knows to grow towards the sunlight, or how its roots always find their way down? Unlike animals with complex nervous systems, plants rely on a sophisticated network of chemical signals – **plant hormones**, also known as **phytohormones**. These remarkable compounds coordinate growth, development, and responses to environmental stimuli, ensuring the plant thrives. In this lesson, we'll dive into the fascinating world of plant control and coordination, focusing on the key hormones and their crucial roles in processes like **phototropism** and **gravitropism**.
Need to know
What you need to know
- **Seed Germination:** When a seed absorbs water, the embryo produces gibberellins. These diffuse to the aleurone layer, stimulating the synthesis of hydrolytic enzymes like amylase. Amylase breaks down stored starch in the endosperm into maltose and glucose, which are used for respiration to provide ATP for the embryo's growth.
- **Stem Elongation:** Active gibberellin (GA1) stimulates stem elongation by causing the breakdown of DELLA protein repressors. DELLA proteins normally inhibit growth genes. By removing them, gibberellins allow for cell division and elongation, leading to an increase in internode length.
Explanation
Control and coordination in plants
- Explain the roles of auxins, gibberellins, abscisic acid (ABA), and ethene in plant growth and development.
- Describe and explain the role of auxins in phototropism of shoots and roots.
- Describe and explain the role of auxins in gravitropism of shoots and roots.