Internal Structure of Dicot Stem - Practice Questions & MCQ

SUMMARY - Internal Structure of Dicot Stem Showing Primary Growth

• The epidermis is the outermost protective layer of the stem.
• Covered with a thin layer of cuticle, it may bear trichomes and a few stomata.
• The cortex has three sub zones: hypodermis, general cortex and endodermis.
• The outer hypodermis, consists of a few layers of collenchymatous cells just below the epidermis, which provide mechanical strength to the young stem.
• Cortical layers below hypodermis consists of rounded thin walled parenchymatous  cells with conspicuous intercellular spaces. 
• The innermost layer of the cortex is called the endodermis. The cells of the endodermis are rich in starch grains and the layer is also referred to as the starch sheath
• The pericycle is present on the inner side of the endodermis and above the phloem in the form of semilunar patches of sclerenchyma.
• In between the vascular bundles there are a few layers of radially placed parenchymatous cells, which constitute medullary rays.
• A large number of vascular bundles are arranged in a ring.
• Each vascular bundle is conjoint, open, and with endarch protoxylem.
• Large number of rounded, parenchymatous cells with large intercellular spaces which occupy the central portion of the stem constitute the pith.

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