why does the epidermis on a leaf have no chloroplasts in it?

Answer 1

The epidermis has numerous functions: protection against various chemical and physical influences, against being fed upon by animals and against infestation by parasites protection of the plant against desiccation participation in gas exchange, in secretion of metabolic compounds and in absorption of water
site of receptors for light and mechanical stimuli that help to transform signals from the surrounding to the plant
The epidermis has accordingly a number of differentiated cell types to serve the various functions.Variations typical for certain species and different organizations of the epidermis in the miscellaneous plant organs add to the number of different cells. Three main types exist:
1. the basic epidermis cell
2. the cells of the stoma complexes and
3. the trichomes (gr.: trichoma = hair), epidermal attachments of varying shape, structure and function

The basic epidermis cells, i.e. the least specialized cells constitute the largest group of dermal cells. They seem either polygonal or elongated in top view. Their walls are often wavy or sinuate. It is unknown, what induces this shape during development, since the explanations given by the existing hypotheses seem insufficient. Elongated epidermis cells can be found at organs or parts of organs that are elongated themselves, like stems, leaf petioles, leaf veins or leaves of monocots. The epidermises of the leaf's upper- and undersurface may have different structures. The shape of the cells, the thickness of the walls as well as the distribution and number of specialized cells (guard cells and trichomes) per area may all vary. Wide varieties of different cell shapes may even exist in species of a single family, e. g. in the Crassulaceae family

The wall of epidermal cells that constitute the leaf's surface is often thicker than the other walls. This can be particularly well observed with the epidermis of conifer needles and that of xerophytes (plants living in dry habitats). Aquatic plants have usually thin walls. The wall of many seeds becomes stronger during ripening and may fill nearly all of the cell's lumen so that the protoplast is driven out and degenerates. The basic epidermal cells of most species contain no chloroplasts. Some ferns and several aquatic or shade plants are exceptions.

The epidermis is more often than not built from a single cell layer, though multi-layered, water-storing epidermises that evolved from initially single-layered tissues by periclinal division have been shown among the species of several families (Moraceae: most Ficus-species, Piperaceae: Peperonia, Begoniaceae, Malvaceae and others). Epidermis cells secrete a cuticle, that covers all epidermal surfaces like an uninterrupted film. It may either be smooth or structured by bulges, rods, filaments, folds, or furrows.
Although leaves are green most of the epidermal cells do not have functional chloroplasts.
In most plants guard cells are the only cells within a leaf's epidermis that contain chloroplasts
It does not function as a photosynthesizing tissue since it has various other primary functions thus in the process of evolution to increase its efficiency it may have lost its chloroplast
Although it should be noted that it is not entirely true that epidermal cell do not have chlp there are always exceptions to any rule in science

Answer 2

Leaf Epidermis

Answer 3

The lack of chloroplast is due to the function of the epidermis. The epidermis is transparent; to allow light to enter, it's waxy to prevent water loss due to evaporation and it is the first barrier for the leaf from the external environment very much like human skin. The epidermis protects, regulates and keeps the leaf airtight.

Answer 4

The absence of chloroplast in the epidermal layers clearly indicate the function of epidermis is not to prepare food but to protect the internal tissues.