Plant Anatomy

Complex Tissues:

A complex plant tissue is made up of more than one type of cells. There are two types of complex plant tissues, viz. xylem and phloem.

Xylem: Xylem is composed of four elements, viz. tracheids, vessels, xylem fibres and xylem parenchyma.


xylem

Primary xylem is of two types, viz. protoxylem and metaxylem. Protoxylem are the first formed primary xylem elements, while the metaxylem are formed later.

  1. Endarch: The protoxylem lies towards the pith in stem and the metaxylem lies towards the periphery. This type of primary xylem is called endarch.
  2. Exarch: The protoxylem lies towards the periphery in roots and the metaxylem lies towards the pith. This type of primary xylem is called exarch.

Transportation of water and minerals from roots to different plant parts is the main function of xylem. Xylem also provides mechanical strength.


Phloem: The phloem; in angiosperms; is composed of four elements, viz. sieve tube, companion cells, phloem parenchyma and phloem fibres. In case of gymnosperms, the phloem has albuminous cells and sieve cells. Sieve tubes and companion cells are absent in the phloem in gymnosperms.

phloem


The primary phloem which is first formed consists of narrow sieve tubes and is called protophloem. The later formed phloem has bigger sieve tubes and is called metaphloem.



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