Cold adaptation acclimation temperature

Plant respiration is a relatively constant proportion of GPP, when ecosystems are compared. Although the respiration rate of any given plant increases exponentially with ambient temperature, acclimation and adaptation counterbalance this direct temperature effect on respiration. Plants from hot environments have lower respiration rates at a given temperature than do plants from cold places (Billings et al., 1971 Billings and Mooney, 1968 Mooney and Bilhngs, 1961). The net result of these counteracting temperature effects is that plants from different thermal environments have similar respiration rates, when measured at their mean habitat temperature (Semikhatova, 2000). 

Exposure to low, non-freezing temperatures induces a process, known as cold acclimation, which makes the plant able to increase its fireezing tolerance. Treatment of wheat, rye and bromegrass cell cultures with ABA for four days at 20°C bypasses the requirement for exposure to low temperature for increased freezing tolerance suggesting that cold acclimation involves ABA. The Arabidopsis aba mutant is unable to cold acclimate by incubation at 4°C but the phenotype can be reverted by treatment with ABA. This shows that adaptation to freezing temperatures requires endogenous ABA. 

Exceptions to cold temperature adaptation being accompanied by shorter chain or more unsaturated fatty acids Include mycelial phospholipids with greater unsaturation when grown at 36 C vs 20 C (77), and the lack of correlation of cold temperature acclimation with Increased lipid unsaturation or membrane fluidity by four fungi representative of four different fungal classes (78). 

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