Bark is not entirely living; it's a complex structure with both living and non-living components.
Understanding Bark's Composition
The outer bark is primarily composed of non-living cells. These dead cells form a protective layer for the tree, shielding it from various threats like insects, diseases, and extreme weather conditions. Think of it like human skin – the outer layer is dead, but crucial for protection. This outer layer is often referred to as rhytidome. Conversely, the inner bark contains living cells, specifically the phloem, which transports nutrients throughout the tree. This inner, living part of the bark is active for a period of time before also becoming part of the non-living outer bark. The cambium layer, located between the inner bark and the wood, is also a living tissue responsible for the tree's growth.
Living Components:
- Inner bark (phloem): Transports sugars and other nutrients produced during photosynthesis.
- Cambium: A thin layer of actively dividing cells responsible for the tree's growth in girth.
Non-living Components:
- Outer bark (rhytidome): Provides protection from environmental stresses and pests. This layer is composed of dead cells.
The Role of Bark
Bark plays a vital role in the overall health and survival of a tree. It acts as:
- Protection: A shield against physical damage, pests, diseases, and extreme temperatures.
- Nutrient Transport: The inner bark facilitates the movement of essential nutrients.
- Water Regulation: Helps control water loss through transpiration.
Practical Insights
When observing a tree, remember that the superficial layer you see is mostly dead tissue, similar to human fingernails. The life of the tree is concentrated in the inner layers, beneath the bark's protective exterior. This explains why damage to the outer bark is often less severe than injuries that penetrate to the living cambium layer.
