Background Soil salinization and alkalization are widespread environmental problems that limit grapevine (Vitis vinifera L.) growth and yield. However, little is known about the response of grapevine to alkali stress. This study investigated the differences in physiological characteristics, chloroplast structure, transcriptome, and metabolome in grapevine plants under salt stress and alkali stress. Results We found that grapevine plants under salt stress and alkali stress showed leaf chlorosis, a decline in photosynthetic capacity, a decrease in chlorophyll content and Rubisco activity, an imbalance of Na+ and K+, and damaged chloroplast ultrastructure. Fv/Fm decreased under salt stress and alkali stress. NPQ increased under salt stress whereas decreased under alkali stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment showed the differentially expressed genes (DEGs) induced by salt stress and alkali stress were involved in different biological processes and have varied molecular functions. The expression of stress genes involved in the ABA and MAPK signaling pathways was markedly altered by salt stress and alkali stress. The genes encoding ion transporter (AKT1, HKT1, NHX1, NHX2, TPC1A, TPC1B) were up-regulated under salt stress and alkali stress. Down-regulation in the expression of numerous genes in the ‘Porphyrin and chlorophyll metabolism’, ‘Photosynthesis-antenna proteins’, and ‘Photosynthesis’ pathways were observed under alkali stress. Many genes in the ‘Carbon fixation in photosynthetic organisms’ pathway in salt stress and alkali stress were down-regulated. Metabolome showed that 431 and 378 differentially accumulated metabolites (DAMs) were identified in salt stress and alkali stress, respectively. L-Glutamic acid and 5-Aminolevulinate involved in chlorophyll synthesis decreased under salt stress and alkali stress. The abundance of 19 DAMs under salt stress related to photosynthesis decreased. The abundance of 16 organic acids in salt stress and 22 in alkali stress increased respectively. Conclusions Our findings suggested that alkali stress had more adverse effects on grapevine leaves, chloroplast structure, ion balance, and photosynthesis than salt stress. Transcriptional and metabolic profiling showed that there were significant differences in the effects of salt stress and alkali stress on the expression of key genes and the abundance of pivotal metabolites in grapevine plants.

Achieving strong light−matter interactions at room temperature is critical for the study of quantum optics and advanced quantum applications. In this paper, we constructed a hybrid system composed of Ag@Au hollow nanocubes (HNCs) and J-aggregates to realize the strong plasmon−exciton interaction at room temperature. First, by changing the shell thickness of Ag@ Au HNCs, we tuned the localized surface plasmon resonance wavelength (λ LSPR ) near the exciton peak (575 nm). Furthermore, there is an obvious anticrossing curve in the hybrid structure, and the Rabi splitting is about 179 meV. Finally, the finite-difference time-domain (FDTD) method was utilized to simulate the absorption spectra of the above nanostructure, and the results matched well with the experimental results. We believe that achieving strong interactions lies in decreasing the volume of the local surface plasmon mode of the Ag@Au HNCs, which is approximately 8645 nm 3 . This work may provide a useful reference value for further exploration of basic optical material research or the development of advanced quantum devices.

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Salt stress and alkali stress were two abiotic stressors which largely impact plant growth and development in grapevine (Vitis vinifera) plants. However, little is known about the mechanisms of grapevine plants response to salt stress and alkaline stress, and whether salt stress and alkali stress have differences in grapevine plants is still unidentified. Thus, we measured physiological parameters, identified chloroplast structure, and analyzed transcriptomics and metabolomics data to characterize the acclimation and difference of grapevine plant under neutral salt stress and alkali salt stress. The results showed that grapevine plants under salt stress and alkali stress were both accompanied by chlorosis of leaf, a decline in photosynthetic capacity, decrease in chlorophyll content and Rubisco activity, imbalance of Na+ and K+, and poorer chloroplast ultrastructure, compared with control. The chlorophyll fluorescence index (Fv/Fm, NPQ) showed the different response to salt stress and alkali stress. Fv/Fm were both decrease in salt stress and alkali stress, whereas NPQ were only decreased in alkali stress. Alkali stress led more serious damage to phenotype, chloroplast microstructure and physiological characteristics in grapevine plants than salt stress. Transcriptomic data showed that salt stress and alkali stress induced the differential expression of stress genes involved in ABA signal and MAPK signal pathways as well as up-regulation of gene encoding ion transporter such as AKT1, HKT1, NHX1, NHX2, TPC1A and TPC1B. However, alkali stress induced more down-regulated genes in ‘Porphyrin and chlorophyll metabolism’, ‘Photosynthesis-antenna proteins’ and ‘Photosynthesis’ pathways compared with salt stress, and both two salt stresses induced many down-regulated DEGs in ‘Carbon fixation in photosynthetic organisms’ pathway. Metabolomics data showed that two substrate involved in chlorophyll synthesis including L-Glutamic acid were down-regulated both under salt stress and alkali stress, but 5-Aminolevulinate (ALA) were only down-regulated under salt stress. In the ‘Carbon fixation in photosynthetic organisms’ pathway, two salt stresses commonly induced the increase of key metabolites including D-Sedoheptuiose 7-phosphate, D-Erythrose-4-phosphate and Dihydroxyacetone phosphate involved in Calvin cycle, but 3-Phospho-D-glyceric acid, D-Fructose 6-Phosphate and Sedoheptulose showed converse change. Many sugar metabolites showed decreased levels under salt stress. However, alkali stress induced an increase in 7 sugar metabolites including Rhamnose, Sedoheptulose, D-Sedoheptulose 7-phosphate, D-Fructose 6-Phosphate, D-Glucose 6-phosphate, Solatriose and Raffinose. Taken together, our results showed that salt stress and alkali stress affected the plant phenotype, chloroplast structure, gene expression and metabolite abundance, and alkali stress resulted in more serious damage to grapevine plants than that of salt stress.