Stems and Leaves

Stem internal structure A vascular bundle is a cord of xylem and phloem running through the stem (it’s thesame one that is found in the root)

Stem Internal Structure Inside each bundle, the phloem is often positioned facing the stem surface; the xylem is positioned facing the stem center.

Stem Internal Structure The vascular bundle is surrounded by ground tissue. Dermal tissue is on the outside of the stem.

Leaf Leaves represent a large surface area that is exposed to sunlight and carbon dioxide for photosynthesis

Leaf Internal Structure

Leaf Internal Structure The cuticle helps to prevent water loss.

Leaf Internal Structure Mesophyll is parenchyma specialized for photosynthesis

Leaf Internal Structure The palisade layer is exposed to direct sunlight Cells in the lower part of the leaf are loosely arranged in the spongy layer (air sacs participate in gaseous exchange)

Leaf Internal Structure Veins (vascular bundles of xylem and phloem) form a network for movement of water, solutes and photosynthetic products throughout the mesophyll

Leaf Internal Structure Stomata are located mostly on the lower epidermis.

Leaf Internal Structure Stomata are surrounded by two guard cells which open and close to regulate transpiration.

Leaf Internal Structure Stomata are typically more abundant on the lower surface of the leaf, and sometimes only found there (except for floating aquatic plants like water lilies)