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Question:

Some vascular bundles are described as open because these:
Are surrounded by pericycle but not to endodermis.
Are capable of producing secondary xylem and phloem.
Possess conjunctive tissue between xylem and phloem.
Are not surrounded by pericycle.

Are surrounded by pericycle but not to endodermis.

Are not surrounded by pericycle.

Are capable of producing secondary xylem and phloem.

Possess conjunctive tissue between xylem and phloem.

Solution:

A vascular bundle in which the phloem and xylem lie on the same radius, with the phloem located toward the periphery of the stem and the xylem toward the centre is called as collateral bundle. Collateral bundles may be closed or open. Closed collateral bundles lack secondary growth, because they contain no cambium. Closed collateral bundles are present in almost all monocotyledonous plants. In open collateral bundles, which are characteristic of the stems of dicotyledonous, gymnospermous, and some pteridoid plants, there is a layer of cambium cells between the phloem and the xylem. As a result of cell division in this layer, new elements of the phloem and xylem are formed (secondary thickening of the stem).Thus, the correct answer is option B.