Final answer:
Hormones like abscisic acid and ethylene regulate the timing and process of leaf loss in deciduous plants.
Step-by-step explanation:
Hormones play a crucial role in leaf loss in deciduous plants. The primary hormone involved in this process is called abscisic acid (ABA). ABA is responsible for triggering the abscission process, which is the detachment of the leaf from the plant. It inhibits the production of auxin, another hormone that promotes leaf retention. When ABA levels increase in response to environmental cues such as shortening daylight hours and cooler temperatures, it signals the cells at the base of the leaf petiole to weaken and undergo cell separation, leading to leaf detachment.
Additionally, ethylene, another hormone, also plays a role in leaf abscission. Ethylene promotes the production of enzymes that break down cell walls, facilitating the detachment of the leaf. It is particularly important in the abscission of flower petals, but it can also contribute to leaf abscission in deciduous plants.