Although it might seem like plants live a carefree life filled with sunbaths and rain showers, most plants live in hostile environments where they have to deal with pests, harsh weather, pollution, and scarce resources. Surviving and even thriving in such environments requires that they adapt and gain advantages that will enable them to:
- Adapt to local conditions like droughts, higher temperatures or increased salinity and
- Bounce back from any injury, e.g. from hail, herbivores or pests.
Plant tolerance is a type adaption that manifests when a plant grows better and stronger than other plants in the same physical setting. This indicates that plant tolerance is a response to abiotic, i.e. physical, stressors.
These natural capacities are often enhanced by humans, e.g. by saving seed from the most fit plants, meaning that there are elements that can be passed on from generation to generation. Accordingly, plant tolerance is considered both an adaption and a defense mechanism.
However, plant tolerance does not necessarily take place at the genetic level, as is the case with plant resistance. Instead, plant tolerance relates to strategies and adaptions from the plant that make it more vigorous and capable of reaching sexual maturity despite environmental challenges.
There are several ways that tolerance in plants manifests:
- Higher net photosynthetic rates after damage
- Growth rates that are higher relative to other plants
- More branching and/or tillering beyond the main stem of the plant
- Maintaining higher levels of carbon storage in roots that can be used for above-ground growth
- Transferring carbon from the roots to the shoots after damage
Most commonly, the concept of plant tolerance is a human construct that relates to agricultural production where plant tolerance is defined as a production level that remains above a particular economic threshold despite the impact of pests, diseases, or inclement weather.
However, there is a natural relationship between herbivores and flora that requires that plants continually tolerate and adapt to their presence. There is a similar relationship between plants and fire.
Nonetheless, as growing conditions throughout the world become less hospitable, e.g. due to rising temperatures, higher salinity and the globalized movement of pests, the importance of plant tolerance is growing – especially for plants living in their natural environments. This is because many plants are forced to more quickly adapt to their changing environments than they would in a situation where local conditions evolve at a natural place.
Thus, in combination with plant resistance, plant tolerance is an evolutionary adaption that continues to play an important role in the growth cycles of plants throughout the world.
- Strauss, S. Y., & Agrawal, A. A. (1999). The ecology and evolution of plant tolerance to herbivory. Trends in Ecology & Evolution, 14(5), 179-185.
- Vinocur, B., & Altman, A. (2005). Recent advances in engineering plant tolerance to abiotic stress: achievements and limitations. Current opinion in biotechnology, 16(2), 123-132.