Basic Cognition of Melatonin Regulation of Plant Growth under Salt Stress: A Meta-Analysis

Research on the Mechanisms of Phytohormone Signaling in Regulating Root Development

Phytohormones are organic compounds produced in trace amounts within plants that regulate their physiological processes. Their physiological effects are highly complex and diverse. They influence processes ranging from cell division, elongation, and differentiation to plant germination and rooting. Therefore, phytohormones play a crucial regulatory role in plant growth and development. Recently, various studies have highlighted the role of PHs, such as auxin, cytokinin (CK), and abscisic acid (ABA), and newer classes of PHs, such as brassinosteroid (BR) and peptide hormone, in the plant responses toward environmental stresses. These hormones not only have distinct roles at different stages of plant growth but also interact to promote or inhibit each other, thus effectively regulating plant development. Roots are the primary organs for water and mineral absorption in plants. During seed germination, the radicle breaks through the seed coat and grows downward to form the primary root. This occurs because the root needs to quickly penetrate the soil to absorb water and nutrients, providing essential support for the plant's subsequent growth. Root development is a highly complex and precisely regulated process influenced by various signals. Changes in root architecture can affect the plant's ability to absorb nutrients and water, which in turn impacts crop yield. Thus, studying the regulation of root development is of great significance. Numerous studies have reported on the role of phytohormones, particularly auxins, in root regulation. This paper reviews recent studies on the regulation of root development by various phytohormones, both individually and in combination, providing a reference for researchers in this field and offering perspectives on future research directions for improving crop yields.

La (NO3)3 substantially fortified Glycyrrhiza uralensis's resilience against salt stress by interconnected pathways

The taproot of Glycyrrhiza uralensis is globally appreciated for its medicinal and commercial value and is one of the most popular medicinal plants. With the decline of wild G. uralensis resources, cultivated G. uralensis has become a key method to ensure supply. However, soil salinization poses challenges to G. uralensis cultivation and affects the yield and quality of it. In this study, the inhibitory effects of NaCl and Na2SO4 on yield and quality of G. uralensis were comprehensively evaluated in a three-year large-scale pot experiment, and the alleviating effects of supplementation with lanthanum nitrate (La (NO3)3) on G. uralensis were further evaluated under salt stress. The findings indicate that La (NO3)3 significantly strengthened the plant's salt tolerance by enhancing photosynthetic capacity, osmolyte accumulation, antioxidant defenses, and cellular balance of ions, which led to a substantial increase in root biomass and accumulation of major medicinal components. In comparison to the NaCl-stress treatment, the 0.75 M La (NO3)3 + NaCl treatment resulted in a 20% and 34% increase in taproot length and biomass, respectively, alongside a 52% and 43% rise in glycyrrhizic acid and glycyrrhizin content, respectively. Similar improvements were observed with 0.75 M La (NO3)3 + Na2SO4 treatment, which increased root length and biomass by 14% and 26%, respectively, and glycyrrhizic acid and glycyrrhizin content by 40% and 38%, respectively. The combined showed that application of La (NO3)3 not only significantly improved the salt resilience of G. uralensis, but also had a more pronounced alleviation of growth inhibition induced by NaCl compared to Na2SO4 stress except in the gas exchange parameters and root growth. This study provides a scientific basis for high-yield and high-quality cultivation of G. uralensis in saline soils and a new approach for other medicinal plants to improve their salt tolerance.

Microplastics change soil properties, plant performance, and bacterial communities in salt-affected soils

Microplastics (MPs) are emerging contaminants found globally. However, their effects on soil-plant systems in salt-affected habitats remain unknown. Here, we examined the effects of polyethylene (PE) and polylactic acid (PLA) on soil properties, maize performance, and bacterial communities in soils with different salinity levels. Overall, MPs decreased soil electrical conductivity and increased NH4+-N and NO3--N contents. Adding NaCl alone had promoting and inhibitive effects on plant growth in a concentration-dependent manner. Overall, the addition of 0.2% PLA increased shoot biomass, while 2% PLA decreased it. Salinity increased Na content and decreased K/Na ratio in plant tissues (particularly roots), which were further modified by MPs. NaCl and MPs singly and jointly regulated the expression of functional genes related to salt tolerance in leaves, including ZMSOS1, ZMHKT1, and ZMHAK1. Exposure to NaCl alone had a slight effect on soil bacterial α-diversity, but in most cases, MPs increased ACE, Chao1, and Shannon indexes. Both MPs and NaCl altered bacterial community composition, although the specific effects varied depending on the type and concentration of MPs and the salinity level. Overall, PLA had more pronounced effects on soil-plant systems compared to PE. These findings bridge knowledge gaps in the risks of MPs in salt-affected habitats.

Multifaceted roles of WRKY transcription factors in abiotic stress and flavonoid biosynthesis

Increasing biotic and abiotic stresses are seriously impeding the growth and yield of staple crops and threatening global food security. As one of the largest classes of regulators in vascular plants, WRKY transcription factors play critical roles governing flavonoid biosynthesis during stress responses. By binding major W-box cis-elements (TGACCA/T) in target promoters, WRKYs modulate diverse signaling pathways. In this review, we optimized existing WRKY phylogenetic trees by incorporating additional plant species with WRKY proteins implicated in stress tolerance and flavonoid regulation. Based on the improved frameworks and documented results, we aim to deduce unifying themes of distinct WRKY subfamilies governing specific stress responses and flavonoid metabolism. These analyses will generate experimentally testable hypotheses regarding the putative functions of uncharacterized WRKY homologs in tuning flavonoid accumulation to enhance stress resilience.