bundle sheath generally contain starch grains. The xylem of the vascular bundle is the spongy cells contain lesser number of chloroplasts. Spongy cells facilitate the exchange of gases with the help of air spaces. The air space that is found next to the stomata is called respiratory cavity or substomatal cavity .
Vascular Tissues Vascular tissues are present in the veins of leaf. Vascular bundles are conjoint, Collateral and closed. Xylem is present towards the upper epidermis, while the phloem towards the lower epidermis. Vascular bundles are surrounded by a compact layer of parenchymatous cells called bundle sheath or border parenchyma .
Xylem consists of metaxylem and protoxylem elements. Protoxylem is present towards the upper epidermis,while the phloem consists of sieve tubes, companion cells and phloem parenchyma. Phloem fibres are absent. Xylem consists of vessels and xylem parenchyma.
Tracheids and xylem fibres are absent. Anatomy of a Monocot Leaf – Grass Leaf A transverse section of a grass leaf reveals the following internal structures. Epidermis The leaf has upper and lower epidermis. They are made up of a single layer of thin walled cells.
The outer walls are covered by thick cuticle. Cuticle Upper epidermis Palisade parenchyma Protoxylem Metaxylem Spongy parenchyma Phloem Bundle sheath Stoma Epidermal hair Lower epidermis Respiratory cavity Figure . : T.S. of Dicot Leaf (Sunflower) located towards the upper epidermis and the phloem towards the lower epidermis.In C grasses, the bundle sheath cells are living and involve in C photosynthesis.
This sheath is called Kranz sheath . Summary A Tissue is a group of cells that are alike in origin, structure and function.There are two principal groups: ( ) Meristematic tissues and ( ) Permanent tissues. Meristematic tissues comprise of self-perpetuating cells. Meristems are classified into several types on the basis of position, origin, function and activity.
Many anatomists illustrated the root and shoot apical meristems on the basis of the type and arrangement and accordingly proposed many theories. The permanent tissues normally develop from apical meristem. They are classified into two types: )Simple permanent tissues and )Complex permanent tissues. Simple