Question

Bark includes?
A. Primary xylem and periderm
B. Primary phloem and primary xylem
C. Periderm & secondary phloem
D. Periderm and pith

Answer 1

Hint: In woody plants, the tissues that are external to the vascular cambium or the tissue that are present outside the wood form the bark. The outer bark is made up of dead tissues and forms a bast. The dead tissues are known as phellogen.

Complete answer: The outermost layer of stems and roots of the woody plants is known as bark. Shrubs, woody vines, and trees have bark. The tissue outside the vascular cambium forms the bark. It consists of outer bark and inner bark which overlays the wood. The living tissues in the older stems form the inner bark and it includes the innermost area of the periderm. The xylem that is formed during the primary growth from the procambium of the apical meristems is also present in the primary xylem. The inner soft bark or bast is derived from the vascular cambium and primarily consists of secondary phloem tissue. The dead cells in the barks are responsible for gaseous exchange and are known as lenticels.
Hence, the correct option is (A)-Primary xylem and periderm

Note: Bark forms the thinner parts than the woody tissues of the stem. Both outer and inner bark is formed by the vascular cambium. The outer bark contains secondary xylem whereas the inner bark contains secondary phloem. The inner bark accumulates dead tissues and the outer bark sloughs off dead tissues.