Concentration of $CO_2$ from nature which is able to induce closure of stomata is

Which of the following is $NOT$ an aim or function of transpiration?

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.

Water stomata are found in

The transpiring organ in plants is

Lewitt's explanation for stomatal action is due to