Dicot LeavesDicot Leaves
Leaves are the main photosynthetic organs of most plants. Dicot leaves generally have a multibranched network of major veins. All leaves have numerous minor cross veins. Xylem is on the top and phloem is located on the bottom.
The leaf is cloaked by its epidermis with cells tightly packed like pieces of a puzzle. Its waxy cuticle makes the epidermis a barrier to the loss of water from the plant. The epidermal barrier is interrupted only by the stomata, tiny pores flanked by guard cells. The stomata allow gas exchange between the surrounding air and the photosynthetic cells inside the leaf, but they are also the major avenue for the loss of water by evaporation.
The ground tissue of a leaf, sandwiched between the upper and lower epidermis is called mesophyll. It consists mainly of parenchyma cells equipped with chloroplasts and specialized for photosynthesis. The leaves of many dicots have two distinctive regions of mesophyll. On the upper half of the leaf is the palisades mesophyll made up of cells that are columnar in shape. Below is the spongy mesophyll which is a labyrinth of spaces through which air circulates.