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Thermotolerance is the ability of an organism to survive high temperatures. An organism's natural tolerance of heat is their basal thermotolerance . [ 1 ] Meanwhile, acquired thermotolerance is defined as an enhanced level of thermotolerance after exposure to a heat stress.
The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature interval (a difference between two temperatures). From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere .
The hardiness scales do not take into account the reliability of snow cover in the colder zones. Snow acts as an insulator against extreme cold, protecting the root system of hibernating plants. If the snow cover is reliable, the actual temperature to which the roots are exposed will not be as low as the hardiness zone number would indicate.
Cymbopogon flexuosus, also called Cochin grass, East-Indian lemon grass or Malabar grass, is a perennial grass native to India, Sri Lanka, Burma, and Thailand.It is placed in the genus Cymbopogon (lemongrasses).
In 2007 it was found that the heat tolerance is conferred to the grass by a symbiosis between a fungus and a virus. When it is colonised by the fungus Curvularia protuberata and the fungus is in turn colonised by a particular virus, the grass is able to tolerate soil temperatures of up to 65 °C that would otherwise be lethal. [ 3 ]
Tender plants are those killed by freezing temperatures, while hardy plants survive freezing—at least down to certain temperatures, depending on the plant. "Half-hardy" is a term used sometimes in horticulture to describe bedding plants which are sown in heat in winter or early spring, and planted outside after all danger of frost has passed.
Generally a temperature rise, above usually 10 to 15 °C above ambient, can be considered heat shock or heat stress. Heat tolerance is broadly defined as the ability of the plant tolerate heat – means that grow and produce economic yield under high temperatures.
Growing degrees (GDs) is defined as the number of temperature degrees above a certain threshold base temperature, which varies among crop species. The base temperature is that temperature below which plant growth is zero. GDs are calculated each day as maximum temperature plus the minimum temperature divided by 2, minus the base temperature.