Question

A student observes grass and Hibiscus plants in his garden during noon. To his surprise, only the leaves of grass were found rolled inwards. The reason could be

• A. presence of more number of stomata on the grass leaves.
• B. undifferentiated mesophyll in grass leaves.
• C. presence of Bulliform cells in the grass leaves.
• D. due to higher rate of transpiration.

Answer 1

The Correct Option is C

(A) Presence of more number of stomata on the grass leaves.

• While grass leaves do have stomata, the presence of more stomata alone does not explain why grass leaves roll inward. Stomata are involved in gas exchange and transpiration, but the rolling mechanism is specifically due to bulliform cells, not just the number of stomata.
• This is not the correct explanation.

(B) Undifferentiated mesophyll in grass leaves.

• Mesophyll refers to the tissue between the upper and lower epidermis of a leaf, where photosynthesis occurs. Whether the mesophyll is differentiated or undifferentiated does not directly relate to the rolling of grass leaves.
• This is not relevant to the phenomenon observed.

(C) Presence of Bulliform cells in the grass leaves.

• Bulliform cells are specialized cells found in grass leaves. These cells are responsible for the rolling mechanism. When water is lost from these cells, they shrink, causing the leaf to curl inward. This is a well-documented adaptation in grasses to reduce water loss under stressful conditions like high temperatures or low soil moisture.
• This is the correct explanation.

(D) Due to higher rate of transpiration.

• While a higher rate of transpiration can contribute to water stress in grass, it does not directly explain why grass leaves roll inward. Transpiration is a general process affecting all plants, but the specific rolling mechanism is driven by bulliform cells in grass leaves.
• This is a contributing factor but not the primary reason for the rolling.

Thus, the correct option is (C): presence of Bulliform cells in the grass leaves.

Answer 2

Grass leaves roll inwards during noon (to reduce water loss), while Hibiscus leaves remain unchanged. This adaptive feature is specific to grasses (monocots) and related to their leaf anatomy.

The rolling of grass leaves is due to bulliform cells, which are absent in broad-leaved plants like Hibiscus. 

Thus, the correct option is C.