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Anatomy of Dicot and Monocot Plants
The anatomy of monocot root is similar to dicot root due to the presence of epidermis, cortex, endodermis, pericycle, vascular bundles and pith. In contrast to dicot root, there are more than six xylem bundles in the monocot root. The pith of monocot roots is large and well-developed. The monocot roots do not exhibit any secondary growth.
The outermost layer of dicot stem is lined with epidermis. The epidermal cells are covered with a thin layer of cuticle bearing trichomes and stomata. The cortex is representated by multiple layers of cells arranged between epidermis and pericycle. The cortex consists of three sub-zones namely, outer hypodermis, cortical layers and endodermis.
Outer hypodermis: The hypodermis is made up of few layers of collenchymatous cells present below the epidermis, providing mechanical strength to the young stem.
Cortical layersare layers of rounded thin wall parenchymatous cells with conspicuous intercellular spaces present beneath the hypodermis.
Endodermis is the innermost layer of the cortex. The cells of the endodermis are rich in starch grains thus referred to as starch sheath. On the inner side of the endodermis, pericycle is present. Above the phloem, the semi-lunar patches of sclerenchymatous cells are present. Between the vascular bundles, there are few layers of parenchymatous cells arranged radially these cells are known as medullary rays. The ring arrangement of vascular bundles is characteristic feature of dicot stem with each vascular bundle being conjoint, open with endarch protoxylem. Pith is defined as several rounded parenchymatous cells with large intracellular spaces that occupy the central portion of the stem.
In monocotyledonous plants, the stem has a sclerenchymatous hypodermis with large number of scattered vascular bundles each surrounded by a sclerenchymatous bundle sheath and a large parenchymatous ground tissue. In monocot stems, the vascular bundles are conjoint and closed. The phloem parenchyma is absent due to which the water-containing cavities are present in the vascular bundles.