ABSTRACT
The establishment of homeostasis associated with the new acclimated state is not the result of a single physiological process but rather the result of many physiological processes that the plant integrates over time, that is, integrates over the acclimation period (Figure 14.1). Plants usually integrate
Acclimatisation of plants exposed to cold temperatures 345
Plants survive freezing temperatures by limiting ice formation 347
Cold-resistant plants tend to have membranes with more unsaturated fatty acids 347
Cold-acclimated plants secrete antifreeze proteins 347 Acclimation of the photosynthetic apparatus due to
high temperatures 348 14.7 Oxygen may protect during acclimation to various
stresses 349 14.8 Plant adaptation to environmental stress 351 Adaptation to heat stress 351 References 353
these physiological processes over a short-term as well as a long-term basis. Short-term acclimations involve responses occurring within minutes of environmental change and typically involve pre-existing components within a biochemical pathway; these responses are easily reversible, for example, increases in enzyme activity (i.e. Calvin cycle) in response to increases in temperature. Long-term acclimation, on the other hand, may begin within minutes, but is pronounced within days or weeks following an environmental change. These responses typically involve altered patterns of gene expression, reallocation of resources between the component processes of photosynthesis, and morphological change. The responses are not immediately reversible and often lead to the development of a visually different phenotype. Long-term responses represent acclimation if they improve performance in the altered environment. Acclimation usually involves the differential expression of specic sets of genes associated with exposure to a particular stress. The remarkable capacity to regulate gene expression in response to environmental change in a time-nested manner is the basis of plant plasticity. A good example is plants growing in shade develop larger leaves and an enhanced photosynthetic apparatus for improved light capture.
