Question

Name the cells that surround a stomatal pore.
A.Palisade parenchyma
B.Spongy parenchyma
C.Guard cells
D.Mesophyll

Answer 1

Hint: Stomata is a structure that is found on the surface of leaves, stems or other plant organs that help in the process of gaseous exchange. This exchange of gases takes place through the stomatal pore.

Complete answer:
The stomatal pore is surrounded by a pair of parenchyma cells known as guard cells that plays an important role in regulating the opening and closing of the stomata and in turn plays a role in the exchange of gases. The stomatal pore is generally closed unless conditions promote their opening. Conditions such as high light intensity or high humidity activates a proton pump that pumps H+ ions out of the guard cells. This makes the cell electrically negative which in turn activates potassium gated channels that pump K+ ion into the cell. Malate ions are also produced and as a result the solute concentration of the guard cell increases which results in movement of water molecules inside the cell due to osmosis. This leads to the opening of the stomatal pore since the guard cells bow apart from one another due to increase in turgor pressure. When the stomatal pore opens carbon dioxide enters into it which is required in photosynthesis and oxygen produced as a product diffuses out through it.

Hence, the correct answer is option (C)

Note: Stomata is present in almost all land plants except liverworts. The distribution of stomata varies between monocot and dicot plants. In dicot plants more stomata are present on the lower surface of the leaves than on the upper surface whereas for monocot plants more or less equal numbers of stomata are present on both the surfaces of leaves.