Globally, different abiotic stresses like heat, heavy metals, flooding, salinity, cold and drought are the major reasons for reduction in development, growth and agriculture crop production [1]. Among all these different abiotic stresses the drought or water scarcity is the most important factor which limits the agriculture crop production [2]. Insufficient availability of water during crop life cycles limits the crop growth and never allows crop to shows its full genetic potential. Mostly every crop is very sensitive to drought stress, mainly during the stage of flowering to seed development. Even drought-resistant crops are negatively affected due to scarcity of water at reproductive and seed development stage [3]. The starting response of drought is closure of stomata which decreases the ability of photosynthesis and final dry matter [4]. Crop gathers proteins and osmolytes mainly intent resilience of stress under conditions of water deficiency and reduces the damage. In addition, plant tolerance equilibrium acts as radicals scavenging and decreases the harmful effects of the cells in abiotic stress conditions [5]. The attributes related to crop morphology such as thickness of roots and its development like ability of crop roots to break compact soil layers, its biomass and depth reduces stress tolerance [6]. It results in lessened germination, growth and seedling development [7] causes death of plant at premature stage [8] and reduces the plant harvestable yield [9]. Many researchers reported the negative effects of water stress on seed germination, growth and development of many crops like sugar beet [10], sunflower [11], kochia [12], sorghum [13] and maize [14]. Therefore, it desired to study the drought mechanism and adopt some strategies to combat drought stress to improve crop production. There are many methods to improve drought tolerance in the crops but application of selenium under drought stress is the best and most economical way to improve drought tolerance and reduce yield losses caused by water scarcity. Selenium is quite similar with Sulphur in several ways such as atomic size, electronegativity and both have similar oxidation states [15]. The Se antioxidant and physiological properties increased the oddity of many agriculture scientists in last few decades. While it does not directly take part in different process of metabolism of plants but helps to decrease the damage of crops under many physiological stresses [16,17].

Different studies confirmed the Se positive role against different abiotic stresses like, high temperature [16], salt [18], senescence [19], cold [20] UV-B [21], heavy metals [22], low water and excess water [23]. Several reports on selenium role for improving drought resistance are scanty. Se can regulate the status of water [24] and significantly increases production of biomass [25] by antioxidant apparatus activation of plants facing water stress. In past few decades literature shows positive effects of selenium at very low concentration in increasing tolerance of plant to drought and improving plants growth [26], increasing carotenoids and chlorophyll contents in leaves of plants [27], regulating status of water [28], compatible solutes accumulation and antioxidant machinery activation. Keeping in mind the importance of selenium, the present review focuses on effect of drought on agriculture crop production and role of selenium for improving crop production under drought conditions.