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 type of photosynthesis used by living organisms. Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of anoxygenic photosynthesis, used mostly by certain types of bacteria, which consume carbon dioxide but do not release oxygen. Carbon dioxide is converted into sugars in a process called carbon fixation; photosynthesis captures energy from sunlight to convert carbon dioxide into carbohydrate. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosyntesis is a process of reduction