Several environmental stresses, including biotic and abiotic factors, adversely affect the growth and development of crops, thereby lowering their yield. However, abiotic factors, e.g., drought, salinity, cold, heat, ultraviolet radiations (UVr), reactive oxygen species (ROS), trace metals (TM), and soil pH, are extremely destructive and decrease crop yield worldwide. It is expected that more than 50% of crop production losses are due to abiotic stresses. Moreover, these factors are responsible for physiological and biochemical changes in plants. The response of different plant species to such stresses is a complex phenomenon with individual features for several species. In addition, it has been shown that abiotic factors stimulate multi-gene responses by making modifications in the accumulation of the primary and secondary metabolites. Metabolomics is a promising way to interpret biotic and abiotic stress tolerance in plants. The study of metabolic profiling revealed different types of metabolites, e.g., amino acids, carbohydrates, phenols, polyamines, terpenes, etc, which are accumulated in plants. Among all, primary metabolites, such as amino acids, carbohydrates, lipids polyamines, and glycine betaine, are considered the major contributing factors that work as osmolytes and osmoprotectants for plants from various environmental stress factors. In contrast, plant-derived secondary metabolites, e.g., phenolics, terpenoids, and nitrogen-containing compounds (alkaloids), have no direct role in the growth and development of plants. Nevertheless, such metabolites could play a significant role as a defense by protecting plants from biotic factors such as herbivores, insects, and pathogens. In addition, they can enhance the resistance against abiotic factors. Therefore, metabolomics practices are becoming essential and influential in plants by identifying different phytochemicals that are part of the acclimation responses to various stimuli. Hence, an accurate metabolome analysis is important to understand the basics of stress physiology and biochemistry. This review provides insight into the current information related to the impact of biotic and abiotic factors on variations of various sets of metabolite levels and explores how primary and secondary metabolites help plants in response to these stresses.

Arbuscular mycorrhizal (AM) fungi are one of the important microbiota involved in a relationship with plant roots in which the plants and fungi both share and exchange nutrients and shelter. Cereal crops are the most essential sources of carbohydrates, dietary protein, and vitamin B for humans, and they supply the most fundamental diets. AM fungi are introduced as the optimal approach for real agricultural systems for increasing growth and productivity. According to a study from the previous decade, AM fungi were shown to promote crop growth and production, particularly in cereal crops. The AM fungi symbiosis provides a pleasant environment for microorganisms in the root and soil system, which promotes plant nutrition and water availability. AM fungi increase nutrient uptake and assimilation and also increase photosynthetic activity, which is directly associated with plant growth. Furthermore, AM fungi increase the primary and secondary metabolites, as well as soluble proteins and carbohydrates, in cereals crops. AM fungi have been shown to improve plant biomass, yield, and productivity in cereal crops. Additionally, the use of AM fungi enhances plants’ stress tolerance against various environmental stresses. In this review, we integrate the recent findings regarding the effects of AM fungi application on soil, root systems, nutrient availability and uptake, photosynthesis, metabolites, plant growth, and productivity. Furthermore, a large number of studies have been reviewed, and several limitations and research gaps have been identified that must be addressed in future studies.