Abiotic stresses affect plants in different ways and are causes of reduction in crop productivity. In order to increase crop productivity it becomes necessary to evolve efficient low-cost technologies for abiotic stress management. Soil microorganisms, surviving in the soil under extreme conditions, have shown great properties, which, if exploited can serve agriculture for increasing and maintaining crop productivity. While it is well established that beneficial soil microorganisms can promote growth and increase productivity through mechanisms such as nutrient mobilization, hormone secretion and disease suppression, it is also becoming increasingly clear that their effects may be more far-reaching. Several studies have reported that soil microorganisms may have mechanisms for alleviation of abiotic stresses in plants such as water and temperature stress, salinity, heavy metals etc. Some of these include tolerance to salinity, drought (Azospirillum sp., Pseudomonas syringae, P. fluorescens, Bacillus sp.) and nutrient deficiency (Bacillus polymyxa, Pseudomonas alacaligenes). Other than bacteria, salinity- and drought-tolerant isolates of Trichoderma harzianum and the effect of other strains of Trichoderma in amelioration of such abiotic stresses have also been reported. Arbuscular mycorrhizal fungi (Glomus mosseae, G. etunicatum, G. intraradices, G. fasciculatum, G. macrocarpum, G. coronatum etc.) help in alleviating abiotic stresses in different crops by enhancing nutrient uptake (phosphorus, nitrogen, magnesium and calcium), biochemical (accumulation of proline, betaines, polyamines, carbohydrates and antioxidants), physiological, molecular and ultra-structural changes. In the present chapter, we attempt an overview of current knowledge on how plant-rhizobacteria, plant-Trichoderma as well as plant-mycorrhiza interactions help in alleviating abiotic stress conditions in different crop systems, which can be used for sustainable agriculture.

Concerns around food security have emerged in recent years, with rising food demand and the options to meet. The FAO projections indicate that global food demand may increase by 70 percent by 2050, with much of the projected increase in demand for major food crops expectedly coming from soaring population and their dietary changes.Moreover, various abiotic stresses accentuated with changing climate has jeopardized the crop production scenario. Ensuring secured food production in the face of climate change is a formidable challenge. Furthermore, in the post-green revolution period, practice of intensive cultivationand extravagant usage of high analysis fertilizers to over-responsive high yielding cultivars have caused havoc micronutrient mining from the soil itself and thus backfired on sustainable food production. In addition to micronutrients, certain beneficial elements are found to be very useful withbetter plant physiology led crop production and nutritive value of the consumables. These elements are collectively referred to as beneficial-trace elements and play a stellar role in moderating various abiotic stresses. Therefore, the application of beneficial-trace elementsas soil and foliar application is needed to be focusedon toassure quality food production through ensuring their effects on crop physiology

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In recent decades the significance of sustainable agriculture has risen to become one of the most important directions in agriculture. In both conventional and sustainable agriculture, plants are exposed to abiotic and biotic factors of the environment. These include factors such as drought, flooding, low temperature, heat, high light intensity, UV-B radiation and soil salinization. Environmental factors that limit plant growth and development are considered as stress factors. Maintaining growth and crop productivity under adverse environmental stresses is presumably the major challenge facing sustainable agriculture. Better understanding physiological and biochemical mechanisms of plant acclimation to stress conditions, and the relationship between plants and environment is the first step to meet this challenge. In this chapter recent information about the plant physiological reaction to different abiotic stress factors, as well as physiological and biochemical bases of acclimation are analysed. It is now known that tolerance to abiotic stress is complex and many authors suggest that the plasticity of cell metabolism and its fast acclimation to changes in environmental conditions is a main essential step in stress tolerance.