Question

Primary xylem is
A.Formed during primary growth
B.Formed before secondary xylem
C.Includes protoxylem and metaxylem
D.All of the above

Answer 1

Hint: Depending upon the structure and function of all cells in a plant, two types of permanent tissues are seen in plants. They are classified as simple permanent tissues and complex permanent tissues. During the primary growth of the plant, the primary xylem is formed from the procambium.

Complete answer:Complex permanent tissues are composed of different types of cells which are fused together to form and perform a single function. The two main types of complex permanent tissues are xylem and phloem. Both xylem and phloem are conducting tissues of the plants which form the vascular bundle. Xylem is a type of vascular tissue that regulates the function of transportation of water from roots to the stem. Xylem tissue is composed of four different types of cells. They are tracheids, vessels, xylem fibers, and xylem parenchyma. The tube-like cells which have a tapering end with a thick wall of the lining of lignin are called xylem tracheid. A central cavity is present in long cylindrical cells called xylem vessels. Xylem fibers are called dead fibers and provide mechanical support. Xylem parenchyma is the only living cell and stores fat and starch. The formation of the primary xylem takes place during primary growth. Primary xylem includes both protoxylem and metaxylem. The secondary xylem is formed from the primary xylem after the metaxylem layer.

So, option D is the correct answer.

Note: Xylem and phloem are conducting vessels of plants that form the vascular bundle. Secondary xylem is present just inner of the vascular cambium and grows towards the pith. Primary xylem is present in all plants but secondary xylem is absent in some plants.