Abiotic stress is defined as the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way. Abiotic stress factors or stressors are naturally occurring, often intangible, factors such as intense sunlight or wind that may cause harm to the plants and animals in the area affected, e.g., Water stress, salt stress, wind stress, heat stress, drought stress, nutrient stress, etc. Stresses can be studied classifying into the following different kinds:

1. Drought stress: It occurs when the available water in the soil is reduced and atmospheric conditions cause continuous loss of water by transpiration or evaporation. Drought stress tolerance is seen in almost all plants but its extent varies from species to species and even within species. Drought stress is characterized by reduction of water content, diminished leaf water potential and turgor loss, closure, nutrient metabolism and growth promoters.
2. Water stress: water stress may result in the arrest of photosynthesis, disturbance of metabolism and finally the death of plant. Water stress inhibits cell enlargement more than cell division. It reduces plant growth by affecting various physiological and biochemical processes, such as photosynthesis, respiration, translocation, ion uptake, carbohydrates, nutrient metabolism and growth promoters
3. Salt stress: there are wild plants that thrive in the saline environments along the sea shore, in estuaries and saline deserts. These plants, called halophytes, have distinct physiological and anatomical adaptations to counter the dual hazards of water deficit and ion toxicity. Salinity can affect any process in the plant's life cycle, so that tolerance will involve a complex interplay of characters. Research projects at Liverpool have investigated details of the physiology and biochemistry of salt tolerance and also looked at methods to screen overall plant performance that could be used in breeding programmes.
4. Heat stress: Heat stress often is defined as where temperatures are hot enough for sufficient time that they cause irreversible damage to plant function or development. In addition, high temperatures can increase the rate of reproductive development, which shortens the time for photosynthesis to contribute to fruit or seed production. I also will consider this as a heat-stress effect even though it may not cause permanent (irreversible) damage to development because the acceleration does substantially reduce total fruit or grain yield.
5. Wind stress: Wind stress is visual stress incurred by wind causes damage to seedlings, breaking branches and even uprooting the whole plants. It helps to covert ground fires to crown fires.
6. Nutrient stress: Nutrient stress is one of the major stresses causing dying back in plants. It causes due to the shortage of nutrients in soil
   such as nitrogen, phosphorus, iron, etc.