Why are vascular bundles closed in monocots ?
Answers
Xylem and phloem of the shoots of mono- and dicots are usually arranged opposite to each other in the vascular bundles (collateral vascular bundles). The xylem is normally at the inside, the phloem at the outside. In dicots, both components are separated by thefascicular cambium. It is also spoken of an open vascular bundle in contrast to the 'closed' bundles of monocots that lack the cambium.
Xylem and phloem are surrounded by a bundle sheath of parenchyma that is often starch-containing. The prime object for the demonstration of structure and arrangement of monocot bundles is the shoot of corn (Zea mays). Although the vascular bundles seem to be scattered in cross-section, do they
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Vascular bundles closed in monocots because vascular cambium is not present.
Explanation:
The vascular system consists of complex tissues, phloem, and xylene. The xylem and the phloem together are vascular bundles of dicotyledonous stems, cambium is present between phloem and xylem. Owing to the presence of cambium, such vascular bundles have the ability to form secondary xylem and phloem tissues and are thus referred to as free vascular bundles.
In monocotyledons, there is no cambium present in the vascular bundles. Therefore, they do not form secondary tissues and are therefore referred to as closed tissues.
Vascular bundles are scattered in the tissues of the ground. They are of different sizes, with the smaller being limited to the periphery. They appear to be embedded in the tissue of the ground. Each vascular bundle is encircled by a bundle sheath made of sclerenchyma. There's no bundle cap in there.
Each vascular bundle is joint, collateral, or lepto centric and closed, i.e. there is no cambium. Protoxylem and metaxylem are arranged in the form of capital 'Y '. Phloem is situated between and above the metalaxyl. Usually, a protoxylem lacuna is formed. In them, secondary vascular tissues are not formed as there is no cambium.
Extra Information:
Vascular bundles typically represent the organization of two vascular tissues, phloem, and xylem. Phloem is a route for dissolved carbohydrates that are transported from tissues that are net producers of photoassimilates to tissues that are net users.
In addition, phloem provides a pathway for translocation of peptides, proteins, and mRNAs involved in plant growth and development and in the defense against pathogens. The xylem is the primary transport mechanism for water and mineral nutrients from the root to the evapotranspiration sites in the shoot system.
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