Onion epidermal cell Onion epidermal cell The epidermal cells of onions provide a protective layer against viruses and fungi that may harm the sensitive tissues. Because of their simple structure and transparency they are often used to introduce students to plant anatomy or to demonstrate plasmolysis. The clear epidermal cells exist in a single layer and do not contain chloroplasts, because the onion fruiting body (bulb) is used for storing energy, not photosynthesis. Each plant cell has a cell wall, cell membrane, cytoplasm, nucleus, and a large vacuole. The nucleus is present at the periphery of the cytoplasm. The vacuole is prominent and
Photosynthesis light, oxidize cytochrome f, chlorophyll a (and other pigments) will absorb another light, but will reduce this same oxidized cytochrome, stating the two light reactions are in series. In 1893, Charles Reid Barnes proposed two terms, "photosyntax" and "photosynthesis", for the biological process of "synthesis of complex carbon compounds out of carbonic acid, in the presence of chlorophyll, under the influence of light". Over time, the term "photosynthesis" came into common usage as the term of choice. Later discovery of anoxygenic photosynthetic bacteria and photophosphorylation necessitated redefinition of the term. After WWII at late 1940 at the University of California,