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Salinity and drought are two significant abiotic stresses that restrict crop production globally. While past research has primarily concentrated on crop responses to individual stresses, recent studies indicate that comprehending the combined effects of drought and salinity is essential for enhancing crop tolerance and productivity. This study aims to investigate the impact of single and combined stresses at varying concentrations of salt and drought on sugar beet. Chlorophyll content, net photosynthesis, stomatal conductance, intercellular CO2, and transpiration in sugar beet increased by 13%, 15%, 4%, and 4%, respectively, while growth parameters also improved under low salinity conditions. Conversely, under drought and high salinity conditions, the carotenoid content and indicators of oxidative damage (malondialdehyde and electrolyte leakage) in sugar beet plants increased significantly by 50% and 67%, respectively, leading to a marked reduction in photosynthesis and severely inhibiting plant growth. However, under the combined effect of low salinity and drought, the relative water content, water potential, and chlorophyll content increased sequentially to 17%, 20%, and 29% percent, photosynthetic efficiency, nutrient content, and potassium (K+) content of the plants increased significantly. On the other hand, sodium (Na+) content decreased significantly compared to the single drought condition. Meanwhile, the activities of antioxidant enzymes, such as catalase, ascorbate peroxidase, peroxidase, and superoxide dismutase, were down-regulated by 10%, 19%, 3%, and 40% sequentially in plants under this combined condition. This suggests that under the combined conditions of low salinity and drought, sugar beet effectively mitigated the negative effects of drought on growth through mechanisms such as improved nutrient uptake, maintenance of water and ion balance, and regulation of antioxidant enzyme activities and that this synergistic effect was mainly attributed to the positive impact of ion balance and osmoregulation. In contrast, the combination of high salinity and drought exacerbated the adverse effects caused by individual stressors. [ABSTRACT FROM AUTHOR]

Aims: Continuous cropping effects are a major constraint to the sugar beet industry. Although the microbial community of continuously cropped sugar beets has been studied, the effect of continuous cropping on microbial symbiotic networks and their function during plant development is unclear. Methods: We analyzed bulk soil and rhizosphere from continuously cropped sugar beet at four growth stages using amplicon and metagenome sequencing and explored the microbial composition, co-occurrence networks, and potential functions of the microbiome at each plant developmental stage. Soil metrics were correlated with microbial communities, and sugar beet from fields with a maize-beet crop rotation acted as a control group. Results: Continuous cropping and the plant developmental stage had far-reaching effects on plant compartment microbial diversity, composition, and cross-kingdom networks, with the strongest effects observed in the rhizosphere of plants at the sugar accumulation stage. Metagenomic analyses further showed that continuous cropping profoundly affects the assembly and function of the soil microbiome at the host developmental stage. Significant changes in the compositions of the fungal and bacterial communities were observed as the plants developed especially during the sugar accumulation stage, as disease-associated pathogens increased and became the core microbial population in the continuously cropped group. Conclusions: Continuous cropping alters the structure of the microbial core population and resulting in very strong selective regulation of the composition and potential function of the soil microbiome during plant development. [ABSTRACT FROM AUTHOR]

Global warming is contributing to an increase in the frequency of extreme climate events, leading to more frequent droughts that pose significant abiotic stressors affecting the growth and yield of sugar beet. To address the detrimental effects of drought stress on sugar beet seedlings, this study simulated a drought environment and examined the impact of arbuscular mycorrhizal fungi (AMF) symbiosis on seedling growth. The findings revealed that AMF inoculation under drought conditions enhanced the photosynthesis rate and increased the content of photosynthetic pigments in the leaves of sugar beet. Additionally, it effectively mitigated cell membrane damage in the seedlings, elevated the levels of osmoregulatory substances, and enhanced antioxidant enzyme activities in both leaves and roots. The inoculation of AMF regulates the physiological processes associated with sugar beet growth, alleviates the adverse effects of drought stress, and promotes seedling development. Consequently, AMF can be regarded as a valuable bioregulator in sugar beet cultivation under drought conditions, providing significant practical benefits for improving sugar beet yield. [ABSTRACT FROM AUTHOR]

Main conclusion: The comparison of the changes of the lipid content in plant cell boundary membranes demonstrates a substantial role of the vacuolar membrane in response to hyperosmotic stress. Comparison of variations in the lipid content of plant cell boundary membranes (vacuolar and plasma membranes) isolated from beet root tissues (Beta vulgaris L.) was conducted after the effect of hyperosmotic stress. Both types of membranes participate in the formation of protective mechanisms, but the role of the vacuolar membrane was considered as more essential. This conclusion was connected with more significant adaptive variations in the content and composition of sterols and fatty acids in the vacuolar membrane (although some of the adaptive variations, especially, in the composition of phospholipids and glycoglycerolipids were similar for both types of membranes). In the plasma membrane under hyperosmotic stress, the increase in the content of sphingolipids was noted that was not observed in the tonoplast. [ABSTRACT FROM AUTHOR]

Main conclusion: Variations in the content of tonoplast microdomains, isolated with the aid of a non-detergent technique, are induced by osmotic stress and may take part in plant cell adaptive mechanisms. Investigation of tonoplast microdomain lipids isolated with the aid of the non-detergent technique from beetroots (Beta vulgaris L.) subjected to either hyperosmotic or hypoosmotic stress was conducted. Earlier, an important role of tonoplast lipids in the protection of plant cells from stress was demonstrated (Ozolina et al. 2020a). In the present paper, we have put forward a hypothesis that lipids of microdomains of raft nature present in the tonoplast are responsible for this protective function. The variations in the content of lipids of the studied nondetergent-isolated microdomains (NIMs) under hyperosmotic and hypoosmotic stresses were different. Under hyperosmotic stress, in the scrutinized microdomains, some variations in the content of lipids were registered, which were characteristic of the already known protective anti-stress mechanisms. These variations were represented by an increase in sterols and polar lipids capable of stabilizing the bilayer structure of the membranes. The found variations in the content of sterols may be bound up with some intensification of the autophagy process under stress because sterols foster the formation of new membrane contacts necessary for this process. Under hypoosmotic stress, the pattern of redistribution of the lipids in the scrutinized membrane structures was different: the largest part of the lipids appeared to be represented by hydrocarbons, which fulfilled mainly a protective function in plants and could prevent the excess water influx into the vacuole. The results obtained not only demonstrate the possible functions of the vacuolar membrane microdomains but also put forward an assumption on the role of any membrane microdomain in the protection mechanisms of the plant cell. [ABSTRACT FROM AUTHOR]

Vacuolar and plasma membranes were isolated by a detergent-free method from beet roots (Beta vulgaris L.), and were fractionated in a sucrose density gradient of 15–60% by high-speed centrifugation at 200,000×g during 18 h. The membrane material distributed over the sucrose density gradient was analyzed for the presence of lipids characteristic of raft structures in different zones of the gradient. The quantitative and qualitative content of lipids and sterols, and the composition of fatty acids were analyzed. Some membrane structures differing in their biochemical characteristics were revealed to be located in different zones of the sucrose gradient. The results of the analysis allowed us to identify three zones in the sucrose gradient after the vacuolar membrane fractionation and two zones in the plasma membrane where membrane structures, which may be defined as rafts for their lipid composition, were presented. [ABSTRACT FROM AUTHOR]

Main conclusion: The vacuolar membrane is an essential component in protecting the plant cell from stress factors. Different variations in the tonoplast lipid content, which depend on the type of stress, have been reviewed. The lipid content of vacuolar membranes of beet roots (Beta vulgaris L.) under hypoosmotic, hyperosmotic and oxidative types of stress has been studied. These types of stress induce variations in the content of almost all the classes of studied lipids (phospholipids, glycoglycerolipids, sterols and fatty acids). The variations, which are characteristic of a single stress, include the variations (i) in the content of individual glycoglycerolipids and in their total content, (ii) in the total content of sterols, and (iii) in the ratio of content of phosphatidylcholine/phosphatidylethanolamine in the scope of tonoplast phospholipids. Variations observed under all of the types of stress under scrutiny include (i) variations in the content of fatty acids of tonoplast lipids, (ii) some decrease in the content of phosphatidic acid and phosphatidylethanolamine, and (iii) variations in the content of individual sterols. Stigmasterol, campesterol, as well as the stigmasterol/sitosterol ratio increased in varying degrees under all of the types of stress. The most substantial variations have been observed in the content of sterols under abiotic stress. This is probably due to role of sterols in regulation of such membrane characteristics as permeability and microviscosity. In our opinion, sterols may represent one of the main components of tonoplast adaptive mechanisms. [ABSTRACT FROM AUTHOR]