You are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will you use to distinguish between the two ?
Secondary xylem
Secondary phloem
Protoxylem
Cortical cells
A vascular bundle without pith is
Vascular bundles in monocotyledons are considered closed because
The vertical section of a dorsoventral leaf through the lamina shows three main parts namely, epidermis, ...$A$... and vascular system. The epidermis, which covers the upper surface is ...$B$... and lower surface is covered by ...$C$... of the leaf.
Choose the correct combination of $A , B$ and $C$
$(i)$ The ...$a$... help in maintaining the pressure gradient in the sieve tubes
$(ii)$ Stomata regulate the process of ....$b$..... and gaseous exchange