$(a)$ $A$ gas is released during photosynthesis. Name the gas and also state the way by which the gas is evolved.
$(b)$ What are stomata? What governs the opening and closing of stomata?

(N/A) The gas released during photosynthesis is $O_2$ (Oxygen).
It is evolved through the photolysis (splitting) of water molecules $(H_2O)$ in the presence of light.
$(b)$ Stomata are tiny pores present on the surface of leaves that facilitate gas exchange.
The opening and closing of stomatal pores are governed by the guard cells.
When water flows into the guard cells, they swell and become turgid, causing the stomatal pore to open.
When the guard cells lose water, they shrink and become flaccid, causing the stomatal pore to close.