Question

Stomatal frequency means
A. Number of stomata per unit area of leaf surface
B. Number of epidermal cells per unit area of leaf surface
C. Number of mesophyll cells per unit area of leaf surface
D. None of the above

Answer 1

Hint: The essential prerequisite to assess the rate of water loss through stomata are a total area of stomata covered in a leaf and determination of stomatal frequency. Stomatal frequency is affected by several genetic and environmental factors. The stomatal frequency decreases where the stomata are large.

Complete answer: Stomatal frequency means the number of stomata present per unit area of a leaf surface. Water availability, carbon dioxide concentration, temperature and light intensity are the environmental factors that change the stomatal frequency. Greater stomatal frequency is a result of water stress. Stomatal frequency is lower in plants growing in wet soil with high humidity than in plants growing in dry soil with low humidity. Pollution of the atmosphere reduces the stomatal frequency, an example is Trifolium pratense. Light intensity plays a vital role in the determination of stomatal frequency. Stomatal frequencies reduce in low light. When a plant grows in full sunlight, the Stomatal frequency becomes higher. Stomatal index refers to the number of stomata to the number of epidermal cells. Stomatal index is found to be reasonably constant for any particular species.
Hence, the correct answer is option A.

Note: The stomatal frequency within a plant is not constant. It keeps changing according to the surrounding environment. Highest stomatal frequencies are often found in those leaves that occur on the top of the plant. The stomatal frequency varies even within a leaf. For example, in grass leaf, the highest stomatal frequency is observed at the point of insertion of the leaf where the cells are still developing and the smallest and lowest at the tip.