Question

Wood of Cycas is
A. Monoxyhc and manoxyhc
B. Manoxylic and polyxylic
C. Diploxyli
D. Monoxylic

Answer 1

Hint: The plants consist of many different cells or tissues that involve many different functions. The vascular tissue is involved in the transportation of water, nutrients, and food throughout the plant. And also involve in the formation of different types of wood in plants.

Complete Answer:
- There are three types of cells that form the plant tissues. They function together to provide food production and storage; give flexibility, support, and strength to the plants. Parenchyma is the most flexible and thin cell found in the plants. They are responsible for the structure of plants and have many other functions like food storage, gas exchange, photosynthesis, and protection.
- The next cell is collenchyma; they are cylindrical in shape and give support around the cell. They consist of unevenly thickened cell walls. This cell retains the ability to process cell division once it matures. The third cell is the sclerenchyma; they lack cytoplasm and other living components get mature. They have thick and rigid cell walls; they involve in providing support to the cell and also help in transportation of materials within the cell.
- The transportation of nutrients, water, and other substances in plants are carried out by tissue like xylem and phloem; they are considered as vascular tissue. Xylem is made of dead cells while phloem is made of living cells.
- Xylem is complex tissues that involve in the transportation of water and other nutrients to the plant while phloem is the tissue involved in the transportation of food and organic matters. The xylem tissue composed of tracheids and fiber while the phloem tissue composed of fibers, sieve cells, sieve tubes, phloem parenchyma, and companion cells. The xylem is found in the centre of the vascular bundle while the phloem tissue is found in the outer cover of the vascular bundle.
- Now, the types of wood found in a plant depends on the amount of xylem cells present in the wood. According to this they are classified as manoxylic and polyxylic. Manoxylic wood is the non-compact wood that consists of a large amount of parenchyma, cortex mixed, and large pith and very less amount of xylem tracheids. Polyxylic wood is a dense wood with a high amount of secondary xylem.
- In the case of Cycas, the stem is manoxylic in the younger age that means it consists of a single ring of vascular bundles but it becomes polyxylic after secondary growth that means it has many rings of secondary vascular tissues.

Thus, the correct answer is ‘B’. Manoxylic and polyxylic.

Note: The manoxylic wood is found in pines. The wood is formed by one ring due to the presence of persistent cambium. In this wood, the pith and cortex are broad, wood is soft, parenchyma is broad, and cambium is short lived.