Bark is the outermost layer of stems and roots in woody plants, encompassing all tissues outside the vascular cambium. Think of it as the plant's protective skin.
Understanding Bark
Bark isn't a single tissue type; it's a complex composite including:
- Inner Bark (Phloem): This living tissue transports sugars produced during photosynthesis from the leaves to other parts of the plant.
- Outer Bark (Rhytidome): This is the dead, protective outer layer. It's made up of layers of dead phloem and cork cells produced by the cork cambium (phellogen).
What Plants Have Bark?
Plants possessing bark include:
- Trees
- Woody vines
- Shrubs
Essentially, any plant with a woody stem will develop bark over time.
Functions of Bark
Bark provides several crucial functions for the plant:
- Protection: Acts as a barrier against physical damage, insect attacks, fungal infections, and extreme temperatures.
- Water Retention: Helps prevent water loss from the stem.
- Waste Storage: Can serve as a place to store metabolic waste products.
- Insulation: Protects the inner tissues from heat and cold.
Key Differences: Inner Bark vs. Outer Bark
| Feature | Inner Bark (Phloem) | Outer Bark (Rhytidome) |
|---|---|---|
| Living/Dead | Living | Dead |
| Function | Transports sugars | Protection |
| Composition | Phloem cells | Dead phloem & cork cells |
In summary, bark is the vital outer layer of woody plant stems and roots, comprising living inner tissues for sugar transport and dead outer tissues for protection.
