What is a Cactus or Succulent? ... 1/2

What is succulence?

What exactly is a succulent plant?

The term succulent refers to a plant that has a capacity to store water in either stems, leaves or roots. They generally come from low rainfall areas (so called "deserts"), or rain may only fall for a few months/weeks of a season with long periods of drought in between, or what rain that does fall is not available readily (e.g. Epiphytes high up in trees in tropical forests, or a plant clinging to the rock face of a cliff), or the soil does not hold any water. Succulents are not a botanical family but an adaption found in many plant families.
In order to survive in these extreme climates, many plants have evolved characteristics whereby they store as much water as possible while it is available, for use later.
As well as storing water, mechanisms must be in place to ensure that precious stored water is not lost. This is done by: Special stems and reduced leaves, CAM metabolism, wide spreading and shallow root sytems, light-colored spines or bloom deposits on leaves/stems which can reflect intense light, a thick cuticle (the outside "skin") and/or sunken stomates (breathing holes).

As mentioned above succulents store water in at least one of three different places: roots, stems, or leaves:

• Leaf succulents are instantly recognisable, shown by the thickness of the plants "leaves" e.g. Agaves, Aloes and Echeverias to name but a few.
• Stem succulents have swollen stems or branches. Cacti and Euphorbias are two examples.
• Root succulents accumulate water in underground storage organs called caudexes. The caudexes are sometimes partially exposed naturally. In cultivation, growers often raise caudexes above the soil for effect (or to prevent rotting).

Xerophytes are plants that are adapted to survive in dry climates, all succulents are basically xerophytes but not all xerophytes are succulents ... succulents have evolved (amongst other things) special enlarged spongy tissue to store water ... other xerophytes have evolved means of conserving water loss e.g. hairs on leaves, reduced leaf size, grey or white leaves, thick leathery leaves, oily leaves, die back of leaves - but are not succulents, they include Acacias, Eucalypts, Creosote Bush, Bromeliads, Yucca and Olives.

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