Goal 2 - Parts of a Leaf Notes
Parts of a leaf (617-621 new, 637-641 old)
The epidermis is the “skin” or outer protective layer of cells on a leaf.
The epidermis is covered with a waxy coating called the cuticle.
Sun light comes from overhead, thus the cells that contain the chloroplasts are located under the top surface of the leaves.
Between the layers of epidermis coated with cuticle, is the mesophyll generally composed of two different types of cells.
A. the palisade mesophyll
B. the spongy mesophyll
The layer of cells just below the epidermis is composed of tightly packed, elongated palisade cells (cookie) that contain chloroplasts (chips in a cookie).
Beneath the palisade layer or layers of cells is a more loose arrangement of more irregular cells with space between them called the spongy mesophyll.
The palisade layer and the spongy mesophyll make up the mesophyll.
The epidermis is the “skin” or outer protective layer of cells on a leaf.
The epidermis is covered with a waxy coating called the cuticle.
- The cuticle keeps the leaf tissue from drying out and protects them from insects and diseases.
Sun light comes from overhead, thus the cells that contain the chloroplasts are located under the top surface of the leaves.
- Most chloroplasts are located in the palisade layer of cells just below the upper epidermis.
Between the layers of epidermis coated with cuticle, is the mesophyll generally composed of two different types of cells.
A. the palisade mesophyll
B. the spongy mesophyll
The layer of cells just below the epidermis is composed of tightly packed, elongated palisade cells (cookie) that contain chloroplasts (chips in a cookie).
- The palisade layer is where most photosynthesis occurs.
Beneath the palisade layer or layers of cells is a more loose arrangement of more irregular cells with space between them called the spongy mesophyll.
- Photosynthesis may occur in the spongy mesophyll, but it is a place where gases are exchanged.
The palisade layer and the spongy mesophyll make up the mesophyll.
Other Parts of the the Leaf
Carbon dioxide is required for photosynthesis and oxygen is a product of the process.
These enter and exit the leaf through openings called the stomata.
The opening and closing of the stomata are regulated by the guard cells.
Stomata are located on the underside of the leaf
Veins run through the mesophyll and are part of the plants plumbing system.
Phloem is located in the bottom portion of the vein and carries food from leaves to the plant.
Xylem is located in the upper portion of the vein and carries water and minerals from the root to the leaf “sucks water”.
These enter and exit the leaf through openings called the stomata.
- The stomata open and close depending on environmental conditions.
The opening and closing of the stomata are regulated by the guard cells.
- Stomata are closed during hot temperatures, dry weather, and darkness.
- Water vapor is also lost through stomata openings.
Stomata are located on the underside of the leaf
- to protect from excess loss of moisture through leaves
- to keep the stomata from being clogged with dust, and
- to prevent easy entry by fungal spores.
Veins run through the mesophyll and are part of the plants plumbing system.
- Veins carry water and nutrients to the leaves and transport away the products of photosynthesis.
- Veins contain phloem and xylem.
Phloem is located in the bottom portion of the vein and carries food from leaves to the plant.
Xylem is located in the upper portion of the vein and carries water and minerals from the root to the leaf “sucks water”.