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Abiotic stress affects living organisms through non-living factors, with plants being more vulnerable due to their inability to move. Plants have developed responses and adaptations to deal with stressors such as drought, seasonal changes, soil factors, and air pollution. Climate change is a major source of stress for crops, leading to research for the development of more resistant crop plants.
Abiotic stress is a term used to describe non-living factors that adversely affect living organisms. Animals can be affected by abiotic stress, but plants are more vulnerable as they are unable to move to a less stressful environment. Biotic stressors would include insect pests and diseases, while abiotic stress of plants results from environmental factors. These can be related to climate – drought, extreme temperatures and wind, for example – or to chemical factors in the soil or atmosphere.
Plants exhibit a series of responses and adaptations that help determine tolerance to abiotic stress. Some of these involve structural or chemical changes, while others involve restricting the growing period based on conditions. In some cases, symbiotic relationships have developed as a response to stressors.
Drought is one of the most common forms of stress encountered by plants and those living in arid or semi-arid areas have developed several strategies to deal with it. One of them is succulence. Thick, fleshy stems and leaves can store large amounts of water and reduce the plant’s surface area to volume ratio, minimizing water loss through evaporation. A waxy coating on the stems and leaves also reduces evaporation. Some non-succulent plants may have long roots that extend down to the groundwater.
Plants can sometimes adapt to seasonal or periodic stresses simply by having a short life cycle that is timed to coincide with the most favorable conditions. For example, a plant may germinate, mature, flower, and produce seed during a short rainy season within an otherwise dry year, or it may lie dormant in an underground tuber for long periods, emerging after rain to quickly complete its life cycle. In temperate areas, the forest floor may be deprived of light for photosynthesis during the summer months, so low-growing forest plants can rapidly complete their life cycles during the spring, before the forest canopy has developed a dense foliage.
Abiotic stress can result from soil factors. A high salt content can be lethal for many plants, but some – known as halophytes – have adapted to brackish conditions, found both in coastal areas, such as salt marshes, and in inland arid areas where high evaporation tends to concentrate the original salts in the mineral content of the soil. These plants can either excrete salt from their leaves or store it within their cells in bodies known as vacuoles so that it is kept separate from the cell cytoplasm. Nutrient deficiencies or the presence of toxic substances such as heavy metals in the soil can also cause abiotic stresses.
Air pollution can be another source of stress. Sulfur dioxide and nitrogen oxides from burning fossil fuels can cause acid rain, which can damage the foliage of sensitive plants. Acid rain can also reduce soil pH, harming or killing plants that aren’t suited to acidic conditions.
Climate change is thought to be a major source of abiotic stress for crops. Changing temperature and rainfall patterns are impacting the growing of food and other crops, with some formerly productive areas suffering from droughts, floods or extreme temperatures. In order to alleviate the economic impact of crop failures, research is underway for the development, through breeding or genetic engineering, of crop plants more resistant to these forms of stress.
