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a After at least 2 h of exposure to cold b After 30 min of heat treatment c Temperature of liquid nitrogen (-196°C)

rather the temperature range of active life is. Plants are much more similar in this respect than they are with regard to their limiting temperatures. Day temperatures (air temperatures) of between 15 and 25 °C and night temperatures of about 10 K lower are, on average, optimal for plant growth. Organisms inhabiting extreme locations, such as snow and ice algae (Haemato-coccus pluvialis, and various Diatomeae) with a life range of between +5 and -5 °C or cyanobacteria and bacteria living in geysers or in the black smokers of the deep sea with optimal temperatures of between +80 and above 100 °C, are exceptions.

Types of organisms constitutively adapted to cold are called psychrophiles and those requiring high temperatures are called thermophiles (or extreme thermophiles), but most organisms are mesophiles.

Not all life processes of a plant have the same optimal temperatures. The temperature requirements of these processes must be adapted to the

Temperature Ranges and Temperatures Limiting Life

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