Xerophytes - adapted to very dry habitats 2. Hydrophytes - adapted to moist habitats, often floating or submerged 3. A. Epidermis - Since leaves are the result of primary growth their dermal system consists of an epidermis 1. Leaves have both an upper and lower epidermis consisting of compactly arranged cells. Hairs called trichomes, may also be present 2.
Most leaves have an epidermis only one cell thick.
However, some xerophytes may have up to three layers of cells. It contains many intercellular air spaces for the diffusion of gasses as well as chloroplasts for photosynthesis. Most of the photosynthetic activity takes place in the palisade layer. Therefore its cells have many more chloroplasts than the spongy layer b. Cells of the spongy layer have fewer chloroplasts than the palisade layer and photosynthetic activity is lower than in the palisade layer.