Correct option is A
Explanation-
A. Wetland plants have structural barrier to prevent O₂ diffusion into soil - Correct.
Wetland (aquatic or semi-aquatic) plants often develop barriers like suberin deposition in root layers that prevent oxygen from diffusing out into the anaerobic surrounding soil. This helps conserve oxygen within the roots for their own metabolism, a crucial adaptation in submerged, low-oxygen environments.
B. Dryland plants have structural barrier to prevent O₂ diffusion into soil - Incorrect.
Dryland (terrestrial) plants do not generally evolve such barriers because oxygen availability in the soil is not a limiting factor. In fact, oxygen diffusion into the soil is essential for root respiration and aerobic microbial activity. So, such a structural barrier is not characteristic of dryland plants.
C. Lowering of cytosolic Ca²⁺ prevents aerenchyma formation - Correct.
Aerenchyma (air space) formation in roots is a common response to flooding. It often requires signaling via cytosolic calcium. A reduction in Ca²⁺ levels inhibits signal transduction required for programmed cell death (PCD), which is key for aerenchyma formation. So, lowering Ca²⁺ would indeed prevent aerenchyma development.
D. Activation of ethylene signal transduction pathway prevents aerenchyma formation - Incorrect.
Actually, ethylene promotes aerenchyma formation. Under hypoxic or waterlogged conditions, ethylene levels rise, triggering PCD in root cortical cells, leading to the development of aerenchyma. Therefore, activation of ethylene signaling facilitates, not prevents, aerenchyma.
The correct statements are: A and C only
So, the correct option is: Option a (A and C only).
