Question

Vascular tissue having abundant vessels and fibers is

• A. Primary xylem
• B. Secondary xylem
• C. Protoxylem
• D. Metaxylem

Answer 1

The correct option is B Secondary xylem

Secondary xylem is formed by vascular cambium and consists of pitted vessels, tracheids, fibre and parenchyma. Cambial activity during secondary growth forms more vessel and tracheids with wider cavities to compensate the demand for additional vessels to supply sap to new leaves, thus it has more vessels as compared to that of primary xylem. It has thick-walled fibres with bordered pits.

The xylem formed first is termed as protoxylem, while metaxylem is developed afterwards present towards the periphery. Protoxylem has tracheids, spiral and scalariform vessels and parenchyma cells while metaxylem has reticulate and pitted vessels with few tracheids. Being the product of primary cell growth, both protoxylem and metaxylem have less number of vessels than that of secondary xylem and lack fibres. Thus, the correct answer is option B.