Phenylmercuric acetate $(PMA)$ results in which of the following effects?

What causes the opening of stomata in plants?

$A$ are structures present in the epidermis of leaves. They regulate the process of transpiration and $B$ exchange. It is composed of two bean-shaped cells known as $C$ cells.
Choose the correct combination of $A, B$ and $C$ from the following options:

Identify the purposes of transpiration.
$I -$ Transpiration creates a transpiration pull for absorption and transport in plants.
$II -$ It supplies water for photosynthesis.
$III -$ It transports minerals from the soil to all parts of the plant.
$IV -$ It cools leaf surfaces by $10-15^{\circ} C$ through evaporation.
$V -$ It maintains the shape and structure of plants by keeping cells turgid.

Transpiration is minimised by the deposition of

Describe the transpiration pull model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?