Cork cambium remains more active during autumn.

Explanation:
The cork cambium is a type of lateral meristem found in the bark of woody plants. It is responsible for the production of cork cells, which make up the outer protective layer of the plant stem. During autumn, several changes occur in the plant's physiology in preparation for the winter season. One of these changes is the formation of a protective layer of cork cells, which helps to protect the plant from harsh environmental conditions.

During autumn, the activity of the cork cambium increases. This increased activity is triggered by various environmental cues such as changes in temperature and day length. The cork cambium starts producing more cork cells, which are dead at maturity and have thick cell walls impregnated with suberin, a waxy substance that makes them impermeable to water and gases.

The increased activity of the cork cambium during autumn is essential for the plant's survival. The cork cells produced by the cork cambium form a protective barrier that prevents the loss of water and nutrients from the stem. This barrier also protects the plant from pathogens, mechanical damage, and extreme temperature fluctuations.

The increased activity of the cork cambium during autumn can be observed through the thickening of the bark. As the cork cells are produced by the cork cambium, they accumulate on the outside of the stem, causing the outer bark to become thicker. This thickening of the bark is particularly noticeable in woody plants such as trees and shrubs.

In conclusion, the cork cambium remains more active during autumn as it produces cork cells that form a protective layer in the plant's stem. This increased activity helps the plant prepare for the harsh conditions of winter and ensures its survival.