Saline–alkali stress seriously endangers the normal growth of cotton (Gossypium hirsutum). Arbuscular mycorrhizal fungi (AMF) could enhance salt tolerance by establishing symbiotic relationships with plants. Based on it, a pot experiment was conducted to simulate a salt environment in which cotton was inoculated with Paraglomus occultum to explore its effects on the saline–alkali tolerance of cotton. Our results showed that salt stress noticeably decreased cotton seedling growth parameters (such as plant height, number of leaves, dry weight, root system architecture, etc.), while AMF exhibited a remarkable effect on promoting growth. It was noteworthy that AMF significantly mitigated the inhibitory effect of salt on cotton seedlings. However, AMF colonization in root and soil hyphal length were collectively descended via salt stress. With regard to osmotic regulating substances, Pro and MDA values in roots were significantly increased when seedlings were exposed to salt stress, while AMF only partially mitigated these reactions. Salt stress increased ROS levels in the roots of cotton seedlings and enhanced antioxidant enzyme activity (SOD, POD, and CAT), while AMF mitigated the increases in ROS levels but further strengthened antioxidant enzyme activity. AMF inoculation increased the photosynthesis parameters of cotton seedling leaves to varying degrees, while salt stress decreased them dramatically. When inoculated with AMF under a salt stress environment, only partial mitigation of these photosynthesis values was observed. Under saline–alkali stress, AMF improved the leaf fluorescence parameters (φPSII, Fv′/Fm′, and qP) of cotton seedlings, leaf chlorophyll levels, and root endogenous hormones (IAA and BR); promoted the absorption of water; and maintained nitrogen balance, thus alleviating the damage from salt stress on the growth of cotton plants to some extent. In summary, mycorrhizal cotton seedlings may exhibit mechanisms involving root system architecture, the antioxidant system, photosynthesis, leaf fluorescence, endogenous hormones, water content, and nitrogen balance that increase their resistance to saline–alkali environments. This study provide a theoretical basis for further exploring the application of AMF to enhance the salt tolerance of cotton.

Arbuscular mycorrhizal fungi (AMF) are beneficial microorganisms ubiquitous in soil that form symbiotic mycorrhizal structures with plant roots. When the host plant is exposed to temperature stress, arbuscular mycorrhizal fungi can improve the host plant’s resistance by helping regulate the growth of underground and aboveground parts. In recent years, due to climate change, extremely high and low temperatures have occurred more frequently and for longer durations, significantly impacting plant growth, antioxidant systems, osmotic balance, photosynthesis, and related gene expression. Consequently, numerous scholars have used arbuscular mycorrhizal fungi to aid plants, confirming that arbuscular mycorrhizal fungi can help host plants improve their ability to resist temperature stress. In this paper, the quantitative research method of Meta-analysis was used to collate and build a database of 129 relevant works to evaluate the effects of AMF on plant resistance to temperature stress and explore the response mechanism of AMF to host plants subjected to temperature stress, providing a theoretical basis for further exploring arbuscular mycorrhizal fungi in improving plant resistance to temperature stress.

A Plant Biostimulant is any substance or microorganism applied to plants to enhance nutrition efficiency, abiotic stress tolerance, and/or crop quality traits, regardless of its nutrient content. The application of Plant biostimulants (PBs) in production can reduce the application of traditional pesticides and chemical fertilizers and improve the quality and yield of crops, which is conducive to the sustainable development of agriculture. An in-depth understanding of the mechanism and effect of various PBs is very important for how to apply PBs reasonably and effectively in the practice of crop production. This paper summarizes the main classification of PBs; The growth promotion mechanism of PBs was analyzed from four aspects: improving soil physical and chemical properties, enhancing crop nutrient absorption capacity, photosynthesis capacity, and abiotic stress tolerance; At the same time, the effects of PBs application on seed germination, seedling vigor, crop yield, and quality were summarized; Finally, how to continue to explore and study the use and mechanism of PBs in the future is analyzed and prospected, to better guide the application of PBs in crop production in the future.