Water shortages and crop responses to drought and salt stress are related to the efficient use of water resources and are closely related to food security. In addition, PEG or NaCl stress alone affect the root hydraulic conductivity (Lpr). However, the effects of combined PEG and NaCl stress on Lpr and the differences among wheat varieties are unknown. We investigated the effects of combined PEG and NaCl stress on the root parameters, nitrogen (N) and carbon content, antioxidant enzymes, osmotic adjustment, changes in sodium and potassium, and root hydraulic conductivity of Yannong 1212, Heng 4399, and Xinmai 19. PEG and NaCl stress appreciably decreased the root length (RL), root surface area (RS), root volume (RV), K⁺ and N content in shoots and roots, and Lpr of the three wheat varieties, while the antioxidant enzyme activity, malondialdehyde (MDA), osmotic adjustment, nonstructural carbon and Na⁺ content in shoots and roots, etc., remarkably remained increased. Furthermore, the root hydraulic conductivity had the greatest positive association with traits such as RL, RS, and N and K⁺ content in the shoots of the three wheat varieties. Moreover, the RL/RS directly and actively determined the Lpr, and it had an extremely positive effect on the N content in the shoots of wheat seedlings. Collectively, most of the root characteristics in the wheat seedlings decreased under stress conditions, resulting in a reduction in Lpr. As a result, the ability to transport nutrients—especially N—from the roots to the shoots was affected. Therefore, our study provides a novel insight into the physiological mechanisms of Lpr.

OsMADS1 plays a vital role in regulating floret development and grain shape, but whether it regulates rice grain quality still remains largely unknown. Therefore, we used comprehensive molecular genetics, plant biotechnology, and functional omics approaches, including phenotyping, mapping-by-sequencing, target gene seed-specific RNAi, transgenic experiments, and transcriptomic profiling to answer this biological and molecular question. Here, we report the characterization of the ‘Oat-like rice’ mutant, with poor grain quality, including chalky endosperms, abnormal morphology and loose arrangement of starch granules, and lower starch content but higher protein content in grains. The poor grain quality of Oat-like rice was found to be caused by the mutated OsMADS1^Olr allele through mapping-by-sequencing analysis and transgenic experiments. OsMADS1 protein is highly expressed in florets and developing seeds. Both OsMADS1-eGFP and OsMADS1^Olr-eGFP fusion proteins are localized in the nucleus. Moreover, seed-specific RNAi of OsMADS1 also caused decreased grain quality in transgenic lines, such as the Oat-like rice. Further transcriptomic profiling between Oat-like rice and Nipponbare grains revealed that OsMADS1 regulates gene expressions and regulatory networks of starch and storage protein metabolisms in rice grains, hereafter regulating rice quality. In conclusion, our results not only reveal the crucial role and preliminary mechanism of OsMADS1 in regulating rice grain quality but also highlight the application potentials of OsMADS1 and the target gene seed-specific RNAi system in improving rice grain quality by molecular breeding.

Drought and salinity stress reduce root hydraulic conductivity of plant seedlings, and melatonin application positively mitigates stress-induced damage. However, the underlying effect of melatonin priming on root hydraulic conductivity of seedlings under drought–salinity combined remains greatly unclear. In the current report, we investigated the influence of seeds of three wheat lines’ 12 h priming with 100 μM of melatonin on root hydraulic conductivity (Lpr) and relevant physiological indicators of seedlings under PEG, NaCl, and PEG + NaCl combined stress. A previous study found that the combined PEG and NaCl stress remarkably reduced the Lpr of three wheat varieties, and its value could not be detected. Melatonin priming mitigated the adverse effects of combined PEG + NaCl stress on Lpr of H4399, Y1212, and X19 to 0.0071 mL·h⁻¹·MPa⁻¹, 0.2477 mL·h⁻¹·MPa⁻¹, and 0.4444 mL·h⁻¹·MPa⁻¹, respectively, by modulating translation levels of aquaporin genes and contributed root elongation and seedlings growth. The root length of H4399, Y1212, and X19 was increased by 129.07%, 141.64%, and 497.58%, respectively, after seeds pre-treatment with melatonin under PEG + NaCl combined stress. Melatonin -priming appreciably regulated antioxidant enzyme activities, reduced accumulation of osmotic regulators, decreased levels of malondialdehyde (MDA), and increased K⁺ content in stems and root of H4399, Y1212, and X19 under PEG + NaCl stress. The path investigation displayed that seeds primed with melatonin altered the modification of the path relationship between Lpr and leaf area under stress. The present study suggested that melatonin priming was a strategy as regards the enhancement of root hydraulic conductivity under PEG, NaCl, and PEG + NaCl stress, which efficiently enhanced wheat resistant to drought–salinity stress.

To understand the distribution of the soil microbial community in natural walnut orchards at different altitude gradients (3000–3500 m) and to reveal the mechanism of the soil microbial activity in natural walnut orchards adapting to high-altitude environments, soil samples from four groups of natural walnut orchards in Gyaca County, southeast Tibet, were studied. Illumina MiSeq sequencing technology was used to analyze the community composition and diversity of soil bacteria and fungi and their responses to the altitudes. The alpha diversity results showed that the vertical distribution pattern of the fungal community was more obvious than that of the bacterial community and the bacterial community diversity first increased (~3364 m) and then decreased with altitude. The number of amplicon sequence variants (ASVs) in the soil bacterial community was significantly higher than that in the fungal community, but soil bacterial and fungal communities in walnut orchards at different altitudes exhibited both inheritance and uniqueness. At the phylum level, the dominant bacterial phyla at different altitudes were Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi (relative abundances > 10.0% in each treatment). With the increase in altitude, the relative abundance of Actinobacteria increased gradually while that of Acidobacteria and Proteobacteria decreased gradually. The dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota (relative abundances >5.0% in each treatment). With the increase in altitude, the relative abundance of Ascomycota increased significantly. At the genus level, the number of dominant bacteria and fungi in the soil decreased gradually with increased altitude and showed anisotropic distribution characteristics. The relative abundances of Actinobacteria among the bacterial phyla—and Olpidiomycota and Zoopagomycota among the fungal phyla—were positively correlated with the altitude (p < 0.05). Most dominant bacterial and fungal phyla were highly significantly (p < 0.01) or significantly (p < 0.05) negatively correlated with the altitude. Soil nitrogen and phosphorus availabilities are the main limiting factors of microbial community diversity. Therefore, altitude caused changes in soil physicochemical properties which directly or indirectly affected the composition and diversity of soil bacterial and fungal communities, and our study provides a theoretical basis for the altitudinal pattern and succession changes in soil microbial communities in the natural walnut orchards of southeast Tibet.

Global warming has led to increased rainfall and waterlogging in some areas, which poses a threat to global food security. The results showed that the negative effects of different waterlogging stresses on different maize were mitigated by spraying exogenous melatonin, which maximally increased POD activity in C 7− 2 maize leaves, SOD activity in ZD 958 maize leaves and CAT activity in Z 58 maize leaves, which in turn reduced MDA in ZD 958 maize leaves and proline content in Z 58 maize leaves, increased antioxidant enzyme activities, and slowed down the damage of the stress on the plant body. Moreover, exogenous melatonin maximally increased chlorophyll b in C 7− 2 maize leaves, chlorophyll and chlorophyll a content of Z 58 maize leaves under CF2 stress, which indicated that melatonin could alleviate the integrity of chloroplast membranes by stress. Meanwhile, exogenous melatonin also increased the stomatal conductance, interstitial carbon dioxide concentration, and transpiration rate of ZD 958, and raised the net photosynthetic rate of C 7 − 2, which enhanced photosynthesis, increased the content of carbohydrates, and directly provided an energy source for the maize growth and metabolism, providing energy source and maintaining cell activity. In conclusion, this study deeply explored the different regulatory effects of melatonin on maize varieties with different genetic backgrounds, showing that waterlogging stress had the least effect on Z 58 maize while melatonin had the best effect on alleviating the damage of ZD 958 under waterlogging stress, followed by Z 58, and lastly C 7 − 2, which deepened the understanding of the molecular mechanism of melatonin in alleviating adversity stress, and provided an opportunity to investigate the mechanism of melatonin action and to optimise its application in agricultural production.