Temperature Stress

We know that temperature alongwith water is an important influence on the geographical distribution and range of organisms. Every organism is restricted to a definite range of temperature, which may be quite dissimilar for different species. In other words, there is an upper and lower lethal temperature above and below which a given organism cannot perform the normal life activities and may suffer irreversible damage or may die.

The lower minimum and upper maximum lethal temperatures and optimum temperature are termed as cardinal temperatures and these vary from species to species. Some organisms have narrow limits of tolerance to high or low temperature (stenothermal) while some tolerate a wide range of temperature (eurythermal) (Figure shown below). Besides tolerance temperature range, organisms have different optimum temperature for growth, development and reproduction i.e. at the specific temperature, they perform specific function with maximum efficiency. The characteristics of terrestrial biotic communities are determined by the temperature and rainfall. Thus we find that different biomes distributed throughout the globe in accordance with the temperature which in turn is influenced by other factors. Since the temperature varies with altitudes as well as with latitude the variation in the vegetation from equator to higher latitudes is somewhat similar to that from planes to higher altitude.

The biomes in different regions have been named according to the kind of vegetation they support such as coniferous forest, deciduous forest, grassland, savanna etc. The deserts and the tundras experience extremes of temperature. The organisms of such biomes survive at the limits of the temperature tolerance. We will now describe the temperature stress on the organisms living in these biomes.