Final answer:
A leaf cross section comprises the upper epidermis with a waxy cuticle, palisade mesophyll with chloroplast-rich cells, spongy mesophyll for gas exchange, lower epidermis with stomata and guard cells, and central vein containing xylem and phloem.
Step-by-step explanation:
Leaf Cross Section Labeling
To label a cross section of a leaf, we need to identify several distinct parts that are involved in the structure and function of the leaf. Starting from the outermost layer, we find the upper epidermis, which is covered by a waxy cuticle to minimize water loss. Beneath the upper epidermis is the palisade mesophyll, consisting of tightly packed columnar cells that contain many chloroplasts, which play a crucial role in photosynthesis.
Beneath the palisade layer is the spongy mesophyll, which is made up of loosely packed, irregularly shaped cells with large air spaces between them, allowing for gas exchange. The lower epidermis is below the spongy mesophyll, and it contains regulated pores called stomata that facilitate gas exchange, with the opening and closing of the stomata controlled by guard cells.
Within the leaf, you will also find the vein, which includes the xylem and phloem. The xylem is responsible for transporting water throughout the plant, while the phloem transports nutrients. These vascular tissues are part of the larger vascular bundle. It's important to note that in many dicot leaves the veins run at various angles, so only the central vein may be clearly visible in the cross section.
The cross section of a leaf includes various structures such as the upper epidermis, lower epidermis, palisade layer, spongy layer, mesophyll, veins (xylem and phloem), and stomata. The upper epidermis is the outermost layer of the leaf, while the lower epidermis contains stomata for gas exchange.
The palisade layer is located just below the upper epidermis and consists of tightly packed columnar cells that contain chloroplasts for photosynthesis. The spongy layer is found below the palisade layer and contains loosely arranged cells with large air spaces for gas exchange.
The mesophyll is the general term used to describe the palisade layer and spongy layer together. The veins, which consist of xylem and phloem, provide support and transport water, nutrients, and sugars throughout the leaf.