Which of the following have sunken stomata?

In plants like Nymphaea which is attached emerged hydrophyte, the stomata are present on

Root cap is a specialized protective structure found on the tips of the terrestrial vascular plants only. The cells of this root cap are

What is the commercial source of cork ? How is it formed in the plant ?

Aerenchyma is helpful in plants by

$A$. According to Clowes root apex consists of an inverted cup like structure.
$B$. Low amount of $RNA$, $DNA$ and protein is characteristic of waiting meristem.
$C$. Cells of reserve meristem can divide only when the root apex gets injured.