Succulent plants, also known as succulents or fat plants, are water-retaining plants adapted to arid climate or soil conditions.
The storage of water often gives succulent plants a more swollen or fleshy appearance than other plants, a characteristic known as succulence. In addition to succulence, succulent plants variously have other water-saving features.
» absent, reduced, or cylindrical-to-spherical leaves
» reduction in the number of stomata
» stems as the main site of photosynthesis, rather than leaves
» compact, reduced, cushion-like, columnar, or spherical growth form
» ribs enabling rapid increases in plant volume and decreasing surface area exposed to the sun
» waxy, hairy, or spiny outer surface to create a humid micro-habitat around the plant, which reduces air movement near the surface of the plant, and thereby reduces water loss and creates shade
» roots very near the surface of the soil, so they are able to take up moisture from very small showers or even from heavy dew
» ability to remain plump and full of water even with high internal temperatures (e.g. 52° Celsius)
» very impervious outer cuticle (skin)
» mucilaginous substances, which retain water abundantly
Many succulents come from the dry areas of the tropics and subtropics, such as steppes, semi-desert, and desert. High temperatures and low precipitation force plants to collect and store water to survive long dry periods. Succulents also occur as epiphytes, "air plants", as such they have limited or no contact with the ground, and are dependent on their ability to store water. Succulents also occur as inhabitants of sea coasts, or salt pans which are exposed to high levels of dissolved minerals that are deadly to many other plant species.
The best known succulents are cacti (family: Cactaceae). Virtually all cacti are succulents, but not all succulents are cacti.
