Question

As a tree grows older which increases more rapidly in thickness?
A. Sapwood
B. Cortex
C. Phloem
D. Heartwood

Answer 1

Hint: As the tree grows older, its girth also increases. The increase in girth leads to an increase in the thickness of the stem of the plant. This increase in girth is due to the increase in the activity of the lateral meristematic tissue present in the plant.

Complete answer:
Sapwood is the outer layer of the secondary wood of the trees. It has live cells present in it. It helps to transport water and minerals to the crown region of the trees. These cells usually have a rich content of water. Sapwood is made up of xylem tissue. As it has high moisture content the sapwood is not used for any wood furniture. They tend to shrink when dried and can easily be affected by the fungi.
Heartwood is present in the core of the trunk of the tree. It is also called the duramen. It is darker in colour as compared to the sapwood. It contains the non-living and the dead cells of the secondary xylem. It stores many substances such as resins and tannins. Heartwood is non-living, resistant to fungal and insect attacks and is durable for making furniture. As the trees grow in size the heartwood also expands in thickness and provides rigidity and strength to the tree.

So, the answer is option D.

Note:
Cortex region is present in between the epidermis or the vascular tissue which are present in the roots and stems. They are the unspecialized cell structure. The phloem belongs to the complex permanent tissue type. It helps in the conduction of food material from the leaves to the other parts of the plant body.