Due to extended periods of below-normal rainfall and rising temperatures, drought is a significant global issue for agricultural productivity. Hydrological, agricultural, and meteorological droughts all pose different problems with regard to the availability of water for important crops, which in turn impacts plant development and yield. Depending on the crop species and stage of maturity, drought stress degrades plant metabolism and physiological processes, resulting in decreased growth and yield losses that can range from 30% to 90%. Acclimatization and adaptation are the two basic techniques that plants use to survive drought. Rapid alterations in physiological processes and chemical composition, including modifications to osmotic pressure, root and leaf size, and antioxidant systems, are all part of acclimatization. Xerophytism and succulence are two characteristics that drought-resistant plants have evolved to assist preserve cellular integrity and water balance in water-limited environments. Even with these tactics, the majority of important crops—such as maize, rice, and wheat—remain extremely vulnerable to drought stress. To lessen the effects of drought, researchers have looked into a number of strategies, including both conventional and cutting-edge methods. Conventional techniques, like the application of plant growth-promoting bacteria (PGPB) and morphological modifications, remain essential for improving drought resilience. Recent breakthroughs have provided innovative alternatives such as nanoparticle (NP) treatments and biochar, which enhance plant resilience. Biochar enhances soil moisture retention and nutrient accessibility, whereas nanoparticles augment water absorption and bolster molecular resilience under stress. Furthermore, microbial inoculants such as plant growth-promoting bacteria (PGPB) enhance nutrient and water absorption, facilitating growth in arid conditions. This review examines the impacts of drought stress on three important staple crops, emphasizing both traditional and novel approaches to lessen the consequences of drought. We highlight how combining insights from ecology, biochemistry, molecular biology, and cutting-edge technologies like biochar and nanoparticles can boost agricultural production and plant resistance in water-scarce environments.

Anaerobic ammonium-oxidizing (anammox) bacteria, aerobic ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) are three groups of ammonium/ammonia-oxidizing prokaryotes (AOPs) that are involved in the nitrogen cycle. This research compared the AOP communities in a constructed freshwater wetland with a natural coastal marine wetland in the subtropical Hong Kong. Both vegetated/rhizosphere and nonvegetated sediments were investigated to identify the effects of different macrophytes on the AOP communities. The polymerase chain reaction (PCR)-amplified gene fragments of 16S rRNA and archaeal and bacterial amoA (encoding the ammonia monooxygenase alpha subunit) were applied as molecular biomarkers to analyze the AOPs’ phylogeny and diversity. Quantitative PCR was used to determine the abundances of AOPs in the sediments. The results showed that the relatively more heterogeneous freshwater wetland contained a broader range of phylotypes, higher diversity, more complex community structures, and more unevenly distributed abundances of AOPs than the coastal wetland. The effects of vegetation on the community structures of AOPs were plant-specific. The exotic Typha angustifolia affected the community structures of all AOPs and enhanced their abundances in the rhizosphere region. Both Phragmites australis and Cyperus malaccensis showed some effects on the community structures of AOB, but minimal effects on those of anammox bacteria or AOA. Kandelia obovata had almost no detectable effect on all AOPs due to their smaller size. This study suggested that the freshwater and coastal marine wetlands may have different contributions to the inorganic N removal due to the variations in AOP communities and plant types.

Mangrove wetlands are an important ecosystem in tropical and subtropical regions, and the sediments may contain both oxic and anoxic zones. In this study, ammonia/ammonium-oxidizing prokaryotes (AOPs) in yellow and black sediments with vegetation and non-vegetated sediments in a mangrove wetland of subtropical Hong Kong were investigated in winter and summer. The phylogenetic diversity of anammox bacterial 16S rRNA genes and archaeal and bacterial amoA genes (encoding ammonia monooxygenase alpha-subunit) were analyzed using PCR amplification and denaturing gradient gel electrophoresis to reveal their community structures. Quantitative PCR was also used to detect their gene abundances. The results showed that seasonality had little effect, but sediment type had a noticeable influence on the community structures and abundances of anammox bacteria. For ammonia-oxidizing archaea (AOA), seasonality had a small effect on their community structures, but a significant effect on their abundances: AOA amoA genes were significantly higher in winter than in summer. In winter, the vegetated yellow sediments had lower AOA amoA genes than the other types of sediments, but in summer, the vegetated yellow sediments had higher AOA amoA genes than the other types of sediments. Sediment type had no apparent effect on AOA community structures in winter. In summer, however, the vegetated yellow sediments showed obviously different AOA community structures from the other types of sediments. For ammonia-oxidizing bacteria (AOB), seasonality had a significant effect on their community structures and abundances: AOB amoA genes in winter were apparently higher than in summer, and AOB community structures were different between winter and summer. Sediment type had little effect on AOB community structures, but had a noticeable effect on the abundances: AOB amoA genes of the vegetated yellow sediments were obviously lower than the black ones in both seasons. This study has demonstrated that seasonality and sediment type affected community structures and abundances of AOPs differently in oxic and anoxic sediments of the mangrove wetland.

Ascorbic acid is a bacteriostatic agent; one of the many ways by which ascorbic acid hampers bacterial growth is by the production of hydrogen peroxide, which further converts into hydroxyl free radicals. Certain amino acids can counteract the inhibitory effect of hydroxyl free radicals by checking their oxidizing effect. Though ascorbic acid is bacteriostatic in nature, it facilitates prokaryotic respiration by decarboxylation. This study was carried out to understand how microbes from different horizons of the forest soil respond to the addition of a bacteriostatic agent (ascorbic acid) and growth promoting agent (amino acids), with respect to the soil respiration. We observed that the addition of either ascorbic acid or a combination of it with amino acid consistently results in increased soil respiration, and this increase is different for different soil types depending on soil composition and origin. Furthermore, we also found that beta alanine-induced maximum respiration in basic soils and L-glutamic in acidic soils. This study is significant because it can be used to explain how a strong reducing sugar, i.e., ascorbic acid, affects the soil respiration mediated via soil microbes. To the best of our knowledge, it is the first report that demonstrates the effect of bacteriostatic and the growth promoting agent together on microbe-mediated soil respiration.