Key Concepts: In dicotyledonous leaves there are two types of mesophyll cells, palisade mesophyll and spongy mesophyll. Palisade mesophyll cells form a layer beneath the upper epidermis whereas spongy mesophyll cells are internal to the lower epidermis. major role of leaf mesophyll cells is to contain large populations of chloroplasts, which carry out photosynthetic carbon assimilation facilitating plant growth. Keywords: palisade mesophyll; spongy mesophyll; airspace; bundle sheath; chloroplast. Figure 1.
A ridge or mountain ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. Ridges are usually termed hills or mountains as well, depending on size.
A plain may be defined broadly as any lowland area that is level or gently sloping or rolling. It normally has few, if any, prominent hills or valleys, but may have considerable slope. A plain may be forested or bare of trees. Many plains around the world are covered in grasses. A plain may be as small as several hundred square feet or as large as hundreds of thousands of square miles. A plateau is another landform that is relatively level, and some sources claim that a plateau is an elevated plain.