are numerous, small and closely arranged in the peripheral portion. Towards the centre, the bundles are comparatively large in size and loosely arranged. Vascular bundles are skull or oval shaped. Phloem The phloem in the monocot stem consists of sieve tubes and companion cells.
Phloem parenchyma and phloem fibres are absent. It can be distinguished into an outer crushed protophloem and an inner metaphloem. Xylem Xylem vessels are arranged in the form of ’Y’ the two metaxylem vessels are located at the upper two arms and one or two protoxylem vessels at the base. In a mature bundle, the lowest protoxylem disintegrates and forms a cavity known as protoxylem lacuna .
Anatomy of a Dicot Leaf-sunflower Leaf Internal structure of dictoyledonous leaves reveal epidermis, Mesophyll and vascular tissues. Epidermis This leaf is generally dorsiventral. It has upper and lower epidermis. The epidermis is usually made up of a single layer of cells that are closely packed.
The cuticle on the upper epidermis is thicker than that of lower epidermis. The minute openings found on the epidermis are called stomata . Stomata Table . : Anatomical differences between dicot stem and monocot stem S.No.
Characters Dicot Stem Monocot Stem . Hypodermis Collenchymatous Sclerenchymatous . Ground tissue Differentiated into cortex, endodermis and pericycle and pith Not differentiated, but it is a continuous mass of parenchyma. .
Starch Sheath Present Absent . Medullary rays Present Absent . Vascular bundles (a) Collateral and open (a) Collateral and closed (b) Arranged in a ring (b) Scattered in ground tissue (c) Secondary growth occurs (c) Secondary growth usually does not occur. are more in number on the lower epidermis than on the upper epidermis.
A stomata is surrounded by a pair of bean shaped cells called guard cells. Each stoma internally opens into an air chamber. These guard cells contain chloroplasts, whereas other epidermal cells do not contain chloroplasts. The main function of the epidermis is to give protection to the inner tissue called mesosphyll .
The cuticle helps to check transpiration. Stomata are used for transpiration and gas exchange. Mesophyll The entire tissue between the upper