Protoxylem vessels are present towards the upper epidermis. The differences between the plants arising from a monocotyledonous seed and from a dicotyledonous seed are very evident. Endarch: Metaxylem lies towards the outer side and protoxylem towards the inner side. In dicot stem, the epidermis is the outermost layer along with the multicellular epidermal stem hairs. Hypodermis The hypodermis in the dicot stem is made up of the collenchyma. Conjoint, collateral, open and endarch vascular bundles ………… Stem c 1. The presence of air spaces is a special feature of spongy cells.
Cambium is a type of lateral meristematic tissues which increases the thickness of the plant through secondary growth. Cork cambium is one-to few cells deep and consists of barrel-shaped, thin-walled cells. The outer walls of the epidermal cells comprise a layer that is termed as cuticle. It is interrupted by the sclerenchymatous patches at certain intervals. Secondary bundles are peripheral in position, small in size, oval in transection and amphivasal, i. Phloem is situated in the form of patches of outer phloem and inner phloem.
Vascular bundles are skull shaped. The vascular tissue forms the skeleton of the leaf and they are known as veins. The remaining portion is parenchymatous ground tissue enclosing the scattered vascular bundles. Phloem parenchyma and phloem fibres are not present. It is well-differentiated into collenchyma, chlorenchyma, parenchyma and endodermis. Cells are polygonal is shape.
Chloroplasts are generally not present. Hypodermis present or absent; if present it is collenchymatous. This layer gives mechanical strength to the plant. A thick uninterrupted cuticle is present on the epidermis. Interfascicular cambium also soon becomes active and cuts internally the row of cells which becomes thick-walled and lignified and are known as conjunctive tissue.
Examples of Monocots and Dicots There are about 65,000 species of monocots. Secondary xylem is present just inner to the cambial ring and consists of mainly thick-walled wood parenchyma and fibres. Four vascular bundles are present in the cortex, situated one each in each protruded bulge. Each vascular bundle is surrounded by a parenchymatous bundle sheath. Endodermis is the innermost layer of cortex. Bougainvillea-Stem: It is circular in outline and exhibits following tissues from outside with-in: Epidermis: 1. These cells are compactly arranged without intercellular spaces.
Chlorenchyma is present below the furrows. Thus the morphological and anatomical features of the leaf help in its physiological functions. Medullary bundles are innermost secondary bundles. They intrude into the secondary xylem, and so the xylem cylinder appears ridged and furrowed. The bundle sheaths, which have the main function to regulate the substances between the parenchyma and vascular tissues, are absent in the dicots. These vascular bundles are wedge in shape. Name the Evolutionary process Models.
It is embody a waxy substance known as cutin. In the sunflower's stem Helianthus , some layers of sclerenchyma cells take place in patches outside the phloem in every vascular bundle. Central tissue is the pith, at foremost part it outlets meals, nonetheless secondarily given mechanical energy to the stem. Monocots and dicots differ in the design of the guard cells; they are dumbbell-shaped in monocots and look like a pair of sausages in dicots. It provides mechanical strength to the plant. Vascular bundles are of different sizes 8. In a mature bundle, the lowest protoxylem disintegrates and forms a cavity known as protoxylem lacuna.
Next to epidermis there are a few layers of parenchyma cells forming the cortex which is immediately followed by a band of chloroplast-containing cells called chlorophyllous tissues. Every vascular bundle is conjoint, collateral, endarch and open. Presence or absence of wood Both herbaceous and woody Herbaceous of seed leaves 2 seed leaves 1 seed leaf Examples Legumes pea, beans, lentils, peanuts daisies, mint, lettuce, tomato and oak are examples of dicots. It consists of primary phloem, secondary phloem, cambium, secondary xylem and primary xylem. Secondary phloem is present in the form of a complete ring and consists of sieve tubes, companion cells and phloem parenchyma. Vascular bundles are skull shaped. The cells are filled with starch grains and lack casparian strips.