Xerophyte

A xerophyte (from Greek ξηρός xeros dry, φυτόν phuton plant) is a species of plant that has adaptations to survive in an environment with little liquid water, such as a desert or an ice- or snow-covered region in the Alps or the Arctic. Popular examples of xerophytes are cacti, pineapple and some Gymnosperm plants. A xerophyte (from Greek ξηρός xeros dry, φυτόν phuton plant) is a species of plant that has adaptations to survive in an environment with little liquid water, such as a desert or an ice- or snow-covered region in the Alps or the Arctic. Popular examples of xerophytes are cacti, pineapple and some Gymnosperm plants. The structural features (morphology) and fundamental chemical processes (physiology) of xerophytes are variously adapted to conserve water, also common to store large quantities of water, during dry periods. Other species are able to survive long periods of extreme dryness or desiccation of their tissues, during which their metabolic activity may effectively shut down. Plants with such morphological and physiological adaptations are xeromorphic. Xerophytes such as cacti are capable of withstanding extended periods of dry conditions as they have deep-spreading roots and capacity to store water. The leaves are waxy and thorny that prevents loss of water and moisture. Even their fleshy stems can store water. Plants absorb water from the soil, which then evaporates from their shoots and leaves; this process is known as transpiration. In dry environments, a typical mesophytic plant would evaporate water faster than the rate of water uptake from the soil, leading to wilting and even death. Xerophytic plants exhibit a diversity of specialized adaptations to survive in such water-limiting conditions. They may use water from their own storage, allocate water specifically to sites of new tissue growth, or lose less water to the atmosphere and so channel a greater proportion of water from the soil to photosynthesis and growth. Different plant species possess different qualities and mechanisms to manage water supply, enabling them to survive. Cacti and other succulents are commonly found in deserts, where there is little rainfall. Other xerophytes, such as certain bromeliads, can survive through both extremely wet and extremely dry periods and can be found in seasonally-moist habitats such as tropical forests, exploiting niches where water supplies are too intermittent for mesophytic plants to survive. Likewise, chaparral plants are adapted to Mediterranean climates, which have wet winters and dry summers. Plants that live under arctic conditions also have a need for xerophytic adaptations, since water is unavailable for uptake when the ground is frozen, such as the European resurrection plants Haberlea rhodopensis and Ramonda serbica. In an environment with very high salinity such as mangrove swamps and semi-deserts, water uptake by plants is a challenge due to the high salt ion levels. Besides that, such environments may cause an excess of ions to accumulate in the cells, which is very damaging. Halophytes and xerophytes evolved to survive in such environments. Some xerophytes may also be considered halophytes, however, halophytes are not necessarily xerophytes. The succulent xerophyte Zygophyllum xanthoxylum, for example, have specialised protein transporters in their cells which allow storage of excess ions in their vacuole to maintain normal cytosolic pH and ionic composition.