In a leaf, where would you expect to find the greatest concentration of chlorophyll?

In a leaf, where would you expect to find the greatest concentration of chlorophyll?

• A. Palisade layer
• B. Lower epidermis
• C. Spongy mesophyll
• D. Vascular bundle

Answer: (A)

Chlorophyll is most abundant where photosynthesis happens most actively, which in a leaf is the palisade mesophyll. These tall, densely packed cells lie just beneath the upper surface and are packed with chloroplasts, so they soak up the most light and drive the bulk of the photosynthetic work. The light has to travel through the upper epidermis first, and the palisade layer is positioned to capture that light efficiently, maximizing the rate of light absorption and thus chlorophyll concentration where it matters most. In contrast, the lower epidermis mainly provides protection and houses stomata for gas exchange; the spongy mesophyll contains air spaces to assist diffusion and has fewer chloroplasts; the vascular bundle is focused on transport and contains little chlorophyll. So the palisade layer stands out as the region with the greatest concentration of chlorophyll.

Chlorophyll is most abundant where photosynthesis happens most actively, which in a leaf is the palisade mesophyll. These tall, densely packed cells lie just beneath the upper surface and are packed with chloroplasts, so they soak up the most light and drive the bulk of the photosynthetic work. The light has to travel through the upper epidermis first, and the palisade layer is positioned to capture that light efficiently, maximizing the rate of light absorption and thus chlorophyll concentration where it matters most.

In contrast, the lower epidermis mainly provides protection and houses stomata for gas exchange; the spongy mesophyll contains air spaces to assist diffusion and has fewer chloroplasts; the vascular bundle is focused on transport and contains little chlorophyll. So the palisade layer stands out as the region with the greatest concentration of chlorophyll.