Abundant pith is characteristic of

Assertion : In collateral vascular bundles, phloem is situated towards inner side.
Reason : In monocot stem, cambium is present

All the following statements regarding sieve tube elements are true except

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:

A vascular bundle without pith is

Write the precise function of

$(a)$ Sieve tube

$(b)$ Interfascicular cambium

$(c)$ Collenchyma

$(d)$ Aerenchyma