The main difference between palisade and spongy mesophyll lies in their structure and function within plant leaves; palisade mesophyll is primarily responsible for light absorption due to its tightly packed, columnar cells, while spongy mesophyll facilitates gas exchange due to its loosely packed, irregularly shaped cells.
Here's a more detailed breakdown:
Structure and Arrangement:
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Palisade Mesophyll: Consists of one or more layers of tightly packed, elongated, columnar cells located directly beneath the upper epidermis of the leaf. This dense arrangement maximizes light absorption.
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Spongy Mesophyll: Located below the palisade mesophyll, characterized by irregularly shaped cells with large intercellular air spaces. These air spaces are crucial for the efficient diffusion of gases (CO2 and O2) within the leaf.
Function:
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Palisade Mesophyll: Primarily responsible for photosynthesis. The tightly packed cells contain a high concentration of chloroplasts, optimizing light capture for the photosynthetic process.
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Spongy Mesophyll: Primarily involved in gas exchange. The large intercellular spaces facilitate the diffusion of carbon dioxide from the stomata to the palisade cells and the diffusion of oxygen from the palisade cells to the stomata. Some photosynthesis also occurs in the spongy mesophyll, but to a lesser extent than in the palisade layer.
Summary Table:
| Feature | Palisade Mesophyll | Spongy Mesophyll |
|---|---|---|
| Cell Shape | Columnar, elongated | Irregular |
| Cell Arrangement | Tightly packed | Loosely packed with large air spaces |
| Location | Beneath the upper epidermis | Below the palisade mesophyll |
| Primary Function | Light absorption and photosynthesis | Gas exchange and some photosynthesis |
| Chloroplast Density | High | Lower (compared to palisade) |
In essence, the palisade mesophyll is optimized for light capture and photosynthesis, while the spongy mesophyll is optimized for gas exchange, working together to support the plant's photosynthetic needs.
