Time Scale of Plant Response to Environment
| March 30, 2024We define stress as an environmental factor that reduces the rate of some physiological process (e.g., growth or photosynthesis) below the maximum rate that the plant could otherwise sustain. Stresses can be generated by abiotic and/or biotic processes.
The immediate response of the plant to stress is a reduction in performance and plants compensate for the detrimental effects of stress through many mechanisms that operate over different time scales, depending on the nature of the stress and the physiological processes that are affected.
Together, these compensatory responses enable the plant to maintain a relatively constant rate of physiological processes despite occurrence of stresses that periodically reduce performance.
If a plant is going to be successful in a stressful environment, then there must be some degree of stress resistance. Mechanisms of stress resistance differ widely among species.
The most meaningful physiological processes to consider are growth and reproduction (survival and reproduction in a competitive environment). To understand the mechanism of plant response, however, we must consider the response of individual processes.
We recognize at least three distinct time scales of plant response to stress:
1. The stress response is the immediate detrimental effect of a stress on a plant process. This generally occurs over a time scale of seconds to days, resulting in a decline in performance of the process
2.Acclimation is the morphological and physiological adjustment by individual plants to compensate for the decline in performance following the initial stress response.
Acclimation occurs in response to environmental change through changes in the activity or synthesis of new biochemical constituents such as enzymes, often associated with the production of new tissue. These biochemical changes then initiate some series of effects that are observed at other levels, such as changes in rate photosynthesis, growth rate of whole plants, and morphology of organs or the entire plant.
Acclimation to stress always occurs within the lifetime of an individual plant, usually within days to weeks.
3. Adaptation is the evolutionary response resulting from genetic changes in populations that compensate for the decline in performance caused by stress. The physiological mechanisms of response are often similar to those of acclimation, because both require changes in the activity or synthesis of biochemical constituents and cause changes in rates of individual physiological processes and growth rate. In fact, adaptation may alter the potential of plants to acclimate to short-term environmental variation. Adaptation, as we define it, differs from acclimation in that it requires genetic changes in populations and therefore typically requires many generations to occur. This is one of the reasons why most stressed plant do not produce to their maximum genetic potentials