STRUCTURE OF LEAVES

STRUCTURE OF LEAVES: 

STRUCTURE OF LEAVES

EXTERNAL STRUCTURE: 

EXTERNAL STRUCTURE

Simple Leaves: 

have a flat, undivided blade that is supported by a stalk called a petiole. The petiole is typically supported by collenchyma and sclerenchyma fibers . Simple Leaves

Compound Leaves: 

blades divided into leaflets that form in one plane and lack axillary buds. Each compound leaf has a single bud at the base of its petiole. There are two kinds of compound leaves: Pinnate Leaves form in pairs along a central stalk-like rachis Palmate Leaves attach at the same point . Compound Leaves

Perfoliate leaves: 

are sessile leaves that surround and are pierced by the stems Perfoliate leaves

Peltate Leaves: 

have petioles that attach to the middle of the blade. Peltate Leaves

INTERNAL STRUCTURE: 

INTERNAL STRUCTURE

Epidermis : 

The epidermis of leaves is a continuous layer of cells on all surfaces of the leaf, unbroken except for pores, the stomata ( stoma , singular), which facilitate the exchange of gases between the interior of the leaf and the atmosphere. Epidermis

Veins (vascular tissue) : 

Veins penetrate all parts of the leaf, forming a network that connects the leaf through the petiole to the vasculature of the stem and thereby to the root as well . Primary xylem cells occupy the upper part of the vein and phloem cells the lower. The vascular tissues are surrounded by a bundle sheath one or two layers thick, composed of fibers in the smaller veins and parenchyma in the larger. Veins (vascular tissue)

Mesophyll : 

The mesophyll tissue forms the bulk of most leaves and the chloroplasts in its cells are the principal sites of photosynthesis . The mesophyll is sandwiched between the epidermal layers. Also called the ground tissue Mesophyll