Question

A collateral vascular bundle, is one in which xylem and phloem strands are present on the same radius with phloem towards

• A. Outer side of the xylem
• B. Inner side of the xylem
• C. All around the xylem
• D. On both sides of the xylem

Answer 1

The correct option is A Outer side of the xylem

A vascular bundle in which a strand of phloem is present external to the strand of xylem on the same radius side by side is known as a collateral bundle. Cambium may be present or absent in between xylem and phloem, and so there are the following two types of a collateral bundle:

(a) Closed collateral bundle: In this type cambium is absent in between xylem and phloem. Therefore stems having this type of bundle does not have normal secondary growth. Ex. Monocotyledonous stem. Usually, these bundles are enclosed within bundle sheath made up of sclerenchyma and those that lack the sheath are considered as anomalous (e.g. Asparagus stem).

(b) Open collateral bundle: An open collateral vascular bundle has cambium called fascicular cambium between xylem and phloem. The bundles can increase in diameter by normal secondary growth with the help of fascicular cambium. Ex. Dicotyledonous stem.

So, the correct answer is 'Outer side of the xylem'.