Identifying dicot leaf structures in transverse section

Steps:

• Examine the section from outer to inner layers, starting with the protective covering.
• Note the layer of elongated, densely packed cells below the upper epidermis for photosynthesis.
• Identify the irregular, air-space-filled cells below for gas exchange.
• Locate the central vascular tissue with xylem and phloem for transport.

Why D is correct:

• D labels the spongy mesophyll, defined as the lower layer with loose cells and air spaces maximizing CO2 diffusion per leaf anatomy.

Why the others are wrong:

• A misidentifies upper epidermis as cuticle only, ignoring its full protective role.
• B confuses palisade mesophyll with vascular bundle, lacking transport vessels.
• C incorrectly places lower epidermis above spongy layer, reversing orientation.

Not enough information on exact choice labels.

Final answer: D