Final answer:
Plants detect changes in the seasons through the length of daylight and respond by changing the color and shedding their leaves in autumn.
Step-by-step explanation:
Plants can detect changes in the seasons by sensing the length of daylight, also known as the photoperiod. In autumn, the days become shorter, which triggers a response in plants. As the days shorten, plants produce less chlorophyll, allowing other leaf pigments such as oranges and yellows to be seen, resulting in the changing colors of tree and shrub leaves.
This seasonal change is a strategy for reducing water loss during periods of extreme dryness. Shedding leaves helps plants conserve energy and matter during the dormant winter months, and they can grow new leaves when spring arrives. Plants can also sense temperature and water availability, along with day length, to determine the time of year and adjust their physiology accordingly.
So, to summarize, plants detect changes in the seasons through the length of daylight and respond by changing the color and shedding their leaves in autumn.