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  • Distinguish between the following:(a) Exarch and endarch condition of protoxylem (b) Stele and vascular bundle (c) Protoxylem and metaxylem (d) Interfasicular cambium and intrafasicular cambium

Distinguish between the following:
(a) Exarch and endarch condition of protoxylem
(b) Stele and vascular bundle
(c) Protoxylem and metaxylem
(d) Interfasicular cambium and intrafasicular cambium
(e) Open and closed vascular bundles
(f) Stem hair and root hair

Answers (1)

(a) Endarch is a protoxylem condition that occurs in the stem of a plant when the protoxylem is arranged in the centre and the metaxylem is arranged at the periphery of the stem. Exarch is a protoxylem condition that occurs in the roots of a plant. In this, the protoxylem lies at the periphery, and the metaxylem is arranged in the centre. This arrangement is called the exarch.

(b) The stele comprises the major part of the root and stem. Stele consists of the vascular bundles, pericycle and the pith. The vascular bundle is a part of the stele consisting of xylem and phloem-types of complex tissues.


(c) There are two kinds of primary xylem- protoxylem and metaxylem. The primary xylem which formed earlier and is smaller in size is the protoxylem and the one which is formed later and is larger is called the metaxylem.


(d) In dicot stems, the cambium cells that are present in between the primary xylem and primary phloem are called the intrafascicular cambium whereas the interfascicular cambium is formed by the adjoining medullary cells with the intrafascicular cambium. This meristematic form is the interfascicular cambium.

(e) A closed vascular bundle lacks cambium and therefore, cannot perform secondary growth whereas an opened vascular bundle has cambium and can very well perform secondary growth.

(f) Stem hairs are trichomes that grow on stems. Trichomes are multicellular epidermal cells, and these can be branched or unbranched and soft or rigid. These protect plants from physical dangers and also help in preventing much loss of water. Root hairs are unicellular epidermal cells present in the roots of the plants. Root hairs help absorb water and important minerals from the soil for the growth of the plant.

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