Which tissue in leaves performs photosynthesis?

esophyll is the primary photosynthetic tissue in leaves.

Definition: Mesophyll is the ground tissue present between the upper (adaxial) and lower (abaxial) epidermis.

Structural Features:

• Composed of chlorophyll-rich parenchyma cells (chlorenchyma)
• Cells contain numerous chloroplasts
• Extensive intercellular spaces for gas exchange

Types of Mesophyll:

1. Dorsiventral Leaves (Dicots):

Mesophyll is differentiated into two zones:

1. a) Palisade Parenchyma:

• Located below adaxial epidermis
• Vertically elongated, columnar cells
• Tightly packed with minimal intercellular spaces
• High chloroplast density (80% of leaf chloroplasts)
• Main site of photosynthesis (maximum light absorption)
• Usually 1-2 layers

1. b) Spongy Parenchyma:

• Located above abaxial epidermis
• Oval or rounded cells
• Loosely arranged with large intercellular spaces and air cavities
• Fewer chloroplasts than palisade
• Facilitates gas exchange (CO₂ diffusion to palisade)

1. Isobilateral Leaves (Monocots):

• Mesophyll is not differentiated
• Uniform parenchymatous cells throughout
• Chloroplasts distributed evenly
• Example: Grasses, monocot crops

Photosynthetic Efficiency:

• C3 plants: Mesophyll performs full Calvin cycle
• C4 plants: Mesophyll fixes CO₂ into C4 acids (Kranz anatomy with bundle sheath chloroplasts)
• CAM plants: Temporal separation (night CO₂ fixation in mesophyll vacuoles)