In a typical leaf, which two mesophyll layers contain chloroplasts and perform most of the photosynthesis?

• A. Xylem and phloem
• B. Palisade mesophyll and spongy mesophyll
• C. Cork cambium and vascular cambium
• D. Upper epidermis and lower epidermis

Answer: (B)

Verified step by step guidance

1. Understand the structure of a typical leaf, which includes several layers such as the upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, and vascular tissues (xylem and phloem).
2. Recall that photosynthesis primarily occurs in cells containing chloroplasts, which are organelles responsible for capturing light energy.
3. Identify which layers have cells rich in chloroplasts: the palisade mesophyll is composed of tightly packed cells with many chloroplasts, making it the main site of photosynthesis.
4. Recognize that the spongy mesophyll, located below the palisade layer, also contains chloroplasts but has loosely arranged cells to facilitate gas exchange, contributing to photosynthesis as well.
5. Conclude that the two mesophyll layers containing chloroplasts and performing most of the photosynthesis are the palisade mesophyll and the spongy mesophyll.