Levélhullás

Levélhullás, also known as leaf fall or defoliation, is a natural process in deciduous plants where leaves are shed. This phenomenon occurs typically in autumn in temperate climates, but can also be triggered by various factors in other seasons. The primary reason for leaf fall in autumn is the shortening of daylight hours and decreasing temperatures, which signal to the plant that winter is approaching.

Before the leaves are shed, deciduous trees and shrubs undergo a period of senescence. During this phase, chlorophyll, the pigment responsible for the green color of leaves, breaks down. This unmasks other pigments, such as carotenoids (yellows and oranges) and anthocyanins (reds and purples), which were present in the leaves all along, leading to the vibrant autumn colors.

As the days grow shorter and colder, the plant forms an abscission layer at the base of the leaf stalk. This layer consists of specialized cells that weaken the connection between the leaf and the branch. Eventually, this layer seals the wound on the branch, preventing water loss and infection. The leaf is then detached from the branch, often falling due to wind or its own weight.

Apart from seasonal changes, levélhullás can also be induced by drought stress, disease, or insect infestation. In such cases, the plant sheds its leaves as a survival mechanism to conserve water and energy. While visually a sign of decline, levélhullás is a crucial part of the life cycle of deciduous plants, allowing them to endure harsh conditions and prepare for new growth in the spring. The fallen leaves contribute to the soil by decomposing and returning nutrients.