1. Dermal Tissue: This is the outermost layer, analogous to skin in animals. It's responsible for:
* Protection: Provides a barrier against external threats like pathogens, insects, and physical damage.
* Regulation: Controls the exchange of gases (like carbon dioxide and oxygen) and water vapor.
* Absorption: In young roots, it helps absorb water and minerals from the soil.
* Secretion: It can produce protective coatings or substances that attract pollinators.
2. Vascular Tissue: This is the transport system of the tree. It consists of two components:
* Xylem: Conducts water and dissolved minerals from the roots to the leaves.
* Phloem: Transports sugars and other organic compounds produced by photosynthesis from the leaves to other parts of the tree, including storage organs.
3. Ground Tissue: This makes up the bulk of the tree's structure and performs a variety of functions:
* Photosynthesis: In leaves, ground tissue contains chloroplasts, which carry out photosynthesis.
* Storage: It can store sugars, starch, and other nutrients.
* Support: It provides structural support for the plant.
* Other functions: It plays a role in gas exchange and hormone production.
Important Note: Some sources may mention a fourth layer called the cambium, but it's not technically a separate tissue layer. The cambium is a meristematic tissue - a zone of rapidly dividing cells that produces both xylem and phloem. It's located within the vascular tissue, specifically between the xylem and phloem.
So, while the cambium is crucial for the tree's growth and development, it's not considered a separate layer in the same way as the dermal, vascular, and ground tissues.
