Thursday, 29 April 2021

Intrafascicular cambium takes part in secondary growth

Intrafascicular cambium takes part in secondary growth

Vascular Strand : It consists of a ring of vascular bundles. The adjacent vascular bundles are separated by medullary rays. Such vascular strand is called eustele. In Cucurbita vascular bundles occur in two alternate rings. Vascular bundles are wedge-shaped in outline with the broader side towards the pericycle and narrower side towards the centre. 

Each vascular bundle is conjoint, that is, it possesses both phloem and xylem. The vascular bundles are collateral with phloem lying on the outer side and xylem towards the inner side with both being present on the same radius. The vascular bundles in Cucurbita are bicollateral. 

A strip of intrafascicular cambium occurs in between a phloem and xylem. Such a vascular bundle is called open vascular bundle. The cambial cells are thin walled and meristematic. They are actually fusiform in outline but appear reƧtangular in T.S. Intrafascicular cambium takes part in secondary growth or formation of secondary vascular tissues.

  It consists of sieve tubes, companion cells, phloem parenchyma and a few phloem fibres. Companion cells control the function of sieve tubes. Phloem parenchyma stores food. It also allows lateral flow of the same.

 Phloem fibres provide mechanical strength. a In phloem, a distinction of protophloem and metaphloem is absent but in xylem distinction into proto xylem and metaxylem is well.

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