OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What does ethene stimulate in a plant?

1. Cell division

2. Leaf expansion and fruit ripening

3. Root elongation

4. Growth of new shoots

The correct answer is: Leaf expansion and fruit ripening

Ethene, also known as ethylene, is a plant hormone that plays a significant role in several physiological processes. It is particularly known for stimulating leaf expansion and fruit ripening. In terms of leaf expansion, ethene influences the growth and development of leaves, allowing them to expand and reach their full size. This is crucial for maximizing photosynthesis and overall plant growth. Moreover, during the ripening process of fruits, ethene acts as a signaling molecule that triggers various biochemical changes. These changes include the breakdown of starches into sugars, softening of the fruit, and the development of aroma and color changes, all of which help to attract animals for seed dispersal. Other options, such as stimulating cell division, root elongation, or the growth of new shoots, are more typically associated with other plant hormones. For example, auxins are primarily responsible for cell elongation and shoot growth, while gibberellins promote seed germination and stem elongation. Therefore, the role of ethene is distinctly characterized by its stimulation of leaf expansion and fruit ripening.