All true plants are multicellular eukaryotes and members of the Kingdom Plantae. All plants extract a majority of their energy autotrophically from sunlight through a process known as photosynthesis.
Plant cells are distinctive and easy to identify. All plant cells have cellulose walls, which strengthen and protect them, as well as a nucleus that is usually offset from the center of the cell. The nucleus contains the plant's DNA, and it is surrounded by organelles that carry out the metabolic processes of the cell. Among these organelles is the chloroplast, which all plants have. The chloroplast is descended from what was once a free-living type of bacteria, and it is the chloroplast that contains the pigment chlorophyll and the substances needed to synthesize sugars from water, sunlight and carbon dioxide.
Photosynthesis is the signature characteristic of plants, and all plants use it to some extent. Plants form the base of the food chain in almost every environment on Earth. All plants take up carbon dioxide and secrete oxygen through holes, usually in their leaves, called stoma. Within these confines, the plant kingdom is very diverse, and such variety exists that few, if any, other traits can be taken as universal among member species.