Question

Medullary rays are made up of.
A. Fibers
B. Tracheids
C. Sclerenchyma cells
D. Parenchymatous cells

Answer 1

Hint: They are sheets of cells running from inside of the plant to outside.

Complete answer:
Medullary rays are the cellular structure that is found in certain species of woods. They appear as radial planar structures, perpendicular to the growth rings.
These medullary rays are generally parenchymatous cells which later transform into xylem and phloem cells.

Additional information
- Medullary rays appear as radiating lines from the center of the wood in the transverse section, in the axial section they may appear as different transverse markings and in the tangential section, these rays are hard to see.
- Medullary rays are formed by the activity of fascicular cambium. During this process, cambium divides and cuts out the cells in both the outer and inner sides.
- Many cells transform into xylem and phloem while certain cells do not, these cells are cut out by the cambium towards the periphery are phloem parenchyma while those towards the pith are xylem parenchyma.
- Both of these xylem parenchyma and phloem parenchyma cells work together as secondary medullary rays.
- These medullary rays are important for the conduction of water, minerals, and other organic substances.
- They also transport substances from the center to the periphery.
- These cells are together known as vascular rays or pith rays.
- They are parenchymatous cells which allow the radial transport of sap and essential in the process of tylosis (outgrowth on parenchyma cells of xylem).

So, the correct answer is Parenchymatous cells.

Note: All the plants have conducting or vascular tissues in the form of xylem and phloem. The main function of these xylems and phloems helps in the transportation of water, minerals, and food respectively. They originate from medullary rays which helps in the radial conduction of substances.