What is a secondary meristem ? One which originates from

Draw illustrations to bring out anatomical difference between

$(a)$ Monocot root and dicot root

$(b)$ Monocot stem and dicot stem

In old trees the greater part of secondary xylem is dark brown and resistant to insect attack due to:

$(a)$ secretion of secondary metabolities and their deposition in the lumen of vessels.

$(b)$ deposition of organic compounds like tannins and resins in the central layers of stem.

$(c)$ deposition of suberin and aromatic substances in the outer layer of stem.

$(d)$ deposition of tannins, gum, resin and aromatic substances in the peripheral layers of stem.

$(e)$ presence of parenchyma cells, functionally active xylem elements and essential oils.

Choose the correct answer from the options given below:

The cross-section of a plant material showed the following features when viewed under the microscope.

$(A)$ The vascular bundles were radially arranged.

$(B)$ Four xylem strands with exarch condition of protoxylem.

To which organ should it be assigned?

Assertion : In angiosperms, the conduction of water is more efficient because their xylem has vessels.
Reason : Conduction of water by vessel elements is an active process with energy supplied by xylem parenchyma rich in mitochondria

$(i)$ The ...$a$... help in maintaining the pressure gradient in the sieve tubes

$(ii)$ Stomata regulate the process of ....$b$..... and gaseous exchange