Bark transpiration is the process of water loss in the form of water vapor through the internal tissues of the plant body, specifically through the bark of the plant body. This vital physiological process allows plants to release excess water into the atmosphere.
Understanding Bark Transpiration
Unlike stomatal transpiration, which primarily occurs through tiny pores (stomata) on leaves, bark transpiration takes place directly through the bark. While often less significant than stomatal transpiration in overall water loss, it plays a notable role, especially in woody plants or during periods when leaves are absent (e.g., deciduous trees in winter).
Key Characteristics and Significance
Based on the provided reference, bark transpiration holds particular importance due to:
- Pathway of Water Loss: It involves the direct passage of water vapor from the plant's internal tissues, through the protective outer bark, and into the surrounding environment. This highlights the bark's role not just as a protective layer but also as a conduit for water movement.
- Contribution Compared to Lenticular Transpiration: The reference explicitly states: "It contributes more than lenticular transpiration as the surface area of the bark is larger."
- Lenticular transpiration occurs through lenticels, which are small, raised pores on the bark of woody stems and fruits, facilitating gas exchange.
- The larger surface area of the bark means that even if the rate of water loss per unit area through the bark is lower than through stomata or lenticels, the sheer expanse of the bark can result in a significant total amount of water transpired. This is particularly relevant for large trees and woody shrubs where bark covers a substantial portion of the plant's above-ground biomass.
Practical Insights
Understanding bark transpiration is crucial for comprehending a plant's overall water balance, especially in environments or seasons where other forms of transpiration might be limited:
- Water Management in Woody Plants: In deciduous trees during winter, when leaves have fallen, bark transpiration can become a primary pathway for water loss, influencing the plant's water status during dormancy.
- Environmental Adaptations: Plants in arid environments or those facing water stress may have adaptations (e.g., thicker bark, waxy coatings on bark) to reduce this form of water loss.
- Physiological Studies: Researchers consider bark transpiration when modeling a plant's total water use and its interaction with the environment. It's a component of the plant's overall transpiration budget.
