**2.1 Drought**

Water scarcity is a significant environmental limitation on plant productivity. Drought-induced crop output losses are likely to outnumber losses from all other sources because both the severity and duration of the stress are crucial [8].

**Figure 1.**

*An overview of major abiotic and biotic stresses [7].*

#### *Stresses in Plants: Biotic and Abiotic DOI: http://dx.doi.org/10.5772/intechopen.100501*

The severity of the drought depends on the occurrence and distribution of rainfall, evaporative demands, and moisture storing capacity of soils, all of which are unpredictable [9]. Nowadays, climate has changed all around the globe by continuously increasing in temperatures and atmospheric CO2 levels. The distribution of rainfall is unequal as a result of climate change, which functions as a major stress in the form of drought. Due to extreme drought conditions, the amount of soil water available to plants is steadily decreasing, causing plants to die prematurely. After drought is imposed on crop plants, growth will be arrested. Drought circumstances cause plants to lower their shoot growth, as well as their metabolic demands [7].

## **2.2 Salt**

One of the most important limiting factors for crop growth and productivity is salt stress. Soil salinity is a global danger to world agriculture because it reduces crop yields and, as a result, crop productivity in salt-affected areas. Salinity is caused by the accumulation of salts in the soil or groundwater over a lengthy period of time as a result of natural processes or through human activities, for example, wethering of rocks or as a result of irrigation schemes using salt-rich irrigation water or having insufficient drainage [10]. There are several ways by which salt stress reduces the growth and yield of crops. Salt stress has two main effects on crop plants: osmotic stress and ion toxicity. These primary effects of salinity stress cause some secondary effects such as assimilate production, reduced cell expansion, and membrane function as well as decreased cytosolic metabolism [2].
