Parts of a Grass Leaf

Organ Structure

• A grass leaf consists of three principle parts: the blade, the sheath and the ligule. Other parts include the collar and auricle. The blade is the expanded part of the leaf and can be flat, V-shaped, rolled inward, thread-like, or boat-shaped. The leaves form from nodes along the plant's stem. The sheath originates at the node and encircles the stem like a tube. It is split down one side and can be separated from the stem without tearing. Some grasses have open sheaths, while others have closed, overlapping sheath margins. The ligule attaches firmly to the stem on the inside of the leaf where the sheath meets the blade and prevents water and dirt from getting between the two. The collar is on the outside of the leaf where the blade and sheath meet. Some grass leaves also have auricles, small appendages found on either side of the blade's base.

Tissue Systems

• Each leaf consists of three tissue systems: the dermal tissue system, the vascular tissue system and the ground or fundamental tissue system. The dermal tissue system protects the leaves and prevents water loss. The vascular tissue system transports food, water and minerals throughout the plant. The ground tissue system provides support, protection and food storage. It is also the part of the leaf where regeneration and photosynthesis occur.

Tissues

• Specific tissues make up each of the three grass leaf tissue systems. The component tissue of the dermal system is the epidermis. It covers the leaf's surface. The vascular system consists of xylem tissue and phloem tissue located in the parallel veins within the leaf. The mesophyll occupies the space between the leaf's upper and lower epidermis and comprises the ground tissue system.

Cells

• Cells make up grass leaf tissues . The epidermis contains epidermal cells and guard cells. Epidermal cells secrete a waxy cuticle that helps prevent plant dehydration. Guard cells regulate water, oxygen and carbon dioxide exchange. Xylem tissue contains tracheids. Tracheids are dead, hollow cells with perforated walls that conduct water and minerals from the plant's roots to the leaves. Companion cells and sieve cells in the phloem conduct food from leaves to the rest of the plant. Parenchyma, collenchyma and sclerechyma cells compose the mesophyll. Parenchyma cells function in storage and photosynthesis. Collenchyma and sclerenchyma cells support the leaf.