Phloem tissue in a leaf is concerned with transport of food materials. Phloem complex permanent tissue is made of sieve tubes and sieve pores, companion cells, phloem parenchyma and phloem fibers. Phloem complex tissue is present towards the lower epidermal surface of the leaf. Xylem in a vascular bundle is concerned with transport of water and minerals. Xylem complex permanent tissue consists of xylem tracheids, xylem vessels, xylem parenchyma and xylem fibers. Xylem tissue of a vascular bundle is present towards the upper epidermis of the leaf. Each vascular bundle consists of xylem and phloem complex tissues surrounded by bundle sheath. They represent the midrib and veins of a leaf. Vascular bundles are present within the mesophyll tissue. both palisade parenchyma and spongy parenchyma include chloroplast as well as chlorophyll concerned with food preparing process photosynthesis. Due to this only, the lower surface of a dicot leaf will be less green in color when compared to upper surface. The cells of spongy parenchyma are with less number of chloroplasts and less quantity of chlorophyll. The cells of spongy parenchyma are loosely arranged with lot of large intercellular spaces in between them. The cells of spongy parenchyma are small in size and irregular in shape. In between the palisade parenmchyma and lower epidermis, spongy parenchyma is present. Due this only, the upper surface of a dicot leaf will be more green in nature when compared to the lower surface. As chloroplasts are more in number in these layer, chlorophyll pigment present also will be more. The cells of this layer internally include more number of chloroplasts in them. The cells are closely packed in each layer with narrow inter cellular spaces in between them. The cells of palisade parenchyma are very much elongated and columnar in nature. This tissue is present in one or two layers. Palisade parenchyma is present just below the upper epidermis. It consists of two tissues- Palisade parenchyma and Spongy parenchyma. Mesophyll is a ground tissue present in between upper epidermis and lower epidermis. Presence of less number of stomata on the upper surface is an adaptation to reduce the loss of water through transpiration. On the upper epidermis less number of stomata are present when compared to the lower epidermis in a dicot leaf. Thick cuticle is mainly meant to check the loss of water through the surface of the leaf. The cuticle present on the upper epidermis is comparatively more thicker than the lower epidermis. Upper epidermis on its outer surface is covered by a thin cuticle. Chloroplasts cannot be seen in these cells. It is a single layered tissue made of cubical cells and arranged closely with no inter cellular spaces in between them. It is the uppermost layer or adaxial layer of a dicot leaf. Structure of a Dicot leaf as observed under a MicroscopeДЄ Transverse Section (T.S.) of a Dicot leaf shows the following internal organization. By taking a thin section of any Dicot leaf, mounting on a clean glass slide after staining and observing it under a normal Compound microscope, we can have a clear picture of the internal structure of a Dicot leaf. To know the physiological activity of the leaf we must have a clear understanding of the internal structure of the leaf. The various tissues present inside the leaf will carry out various functions. These tissues are arranged in a definite pattern internally in the leaf. Internally the leaf consists of various tissues. Anatomy is the study of the internal structure of an organ. Leaf is an important bifacial (two surfaced) photosynthetic organ of a plant.

Internal leaf structure and functions