Question

Heartwood and sapwood consist of

(A) bark.

(B) periderm.

(C) secondary xylem.

(D) secondary phloem.

Short answer

(A)The option “bark” isincorrect.

(B)The option “periderm” isincorrect.

(C)The option “secondary xylem” iscorrect.

(D)The option “secondary phloem” is incorrect.

Step-by-step solution

Heartwood and sapwood

Heartwood is the central part of the trunk that functions as a storage of biochemicals which may differ in different plants.The plant's mechanical support comes from the heartwood.

Sapwood is the light-colored outer layer of bark of the tree through which water flows from the roots to the leaves and where surplus food is frequently stored. It performs all the physiological activities, such as the transport of water and nutrients.

Explanation of option ‘(A)’

Heartwood and sapwood do not possess a bark as both the heartwood and softwood are parts of the bark. The outer layer of the bark is the softwood, and the inner layer that is the core of the bark is softwood.

Thus, heartwood and softwood do not consist of bark.

Therefore, the given option is incorrect.

Explanation of option ‘(B)’

The role of the periderm is to keep pathogens away from the plant. It is the outer layer of stems and roots that prevents excessive water loss. They also protect the plants from biotic and abiotic stresses.

Thus, heartwood and sapwood do not consist of the periderm.

Therefore, the given option is incorrect.

Explanation of option ‘(C)’

The role of heartwood and sapwood is to carry the water from the roots to the leaves, so it possesses the vascular tissue xylem. The function of the xylem is to transport water from the roots to all the other parts of the plant.

Thus, heartwood and sapwood consist of secondary xylem.

Therefore, the given option is correct.

Explanation of option ‘(D)’

Phloem is made up of primary and secondary phloem. The role of secondary phloem, a vascular tissue, is to carry stored starch as a nutrient for all the parts of the plant. The role of primary phloem is to form a procambium during primary growth.

Thus, heartwood and sapwood do not consist of the secondary phloem.

Therefore, the given option is incorrect.