Plant hormones

Plant hormones, also known as phytohormones, are chemical messengers that regulate growth, development, and responses to environmental stimuli in plants. In the WJEC GCSE Biology course, you will focus on auxins, gibberellins, and ethene (ethylene). Auxins control phototropism (growth towards light) and gravitropism (growth in response to gravity), while gibberellins promote seed germination and stem elongation. Ethene is a gas that speeds up fruit ripening and leaf fall. Understanding these hormones is crucial for explaining how plants adapt to their surroundings and for applications in agriculture and horticulture, such as using rooting powders or controlling fruit ripening.

This topic builds on your knowledge of plant cells and tissues, and it connects to broader concepts like homeostasis and response mechanisms in organisms. By studying plant hormones, you will see how even simple organisms use chemical signals to coordinate complex behaviours. In exams, you are expected to describe experiments that demonstrate tropisms, explain the role of auxins in bending responses, and evaluate the use of plant hormones in commercial settings. Mastering this topic will help you appreciate the sophistication of plant life and its practical importance in food production and gardening.

Plant hormones are a key part of the 'Response and Regulation' unit in WJEC GCSE Biology. They illustrate the principle that all living things must respond to changes in their environment to survive. For plants, which cannot move, hormonal control is essential for optimising growth towards light and water. This topic also introduces the idea of using scientific knowledge to solve real-world problems, such as using synthetic auxins as weedkillers or gibberellins to produce seedless grapes. By the end of this topic, you should be able to explain how these hormones work at a cellular level and apply your understanding to unfamiliar scenarios.