Phosphorus and Serendipita indica synergism augments arsenic stress tolerance in rice by regulating secondary metabolism related enzymatic activity and root metabolic patterns.

The multifarious problems created by arsenic (As), for collective environment and human health, serve a cogent case for searching integrative agricultural approaches to attain food security. Rice (Oryza sativa L.) acts as a sponge for heavy metal(loid)s accretion, specifically As, due to anaerobic flooded growth conditions facilitating its uptake. Acclaimed for their positive impact on plant growth, development and phosphorus (P) nutrition, 'mycorrhizas' are able to promote stress tolerance. Albeit, the metabolic alterations underlying Serendipita indica (S. indica; S.i) symbiosis-mediated amelioration of As stress along with nutritional management of P are still understudied. By using biochemical, RT-qPCR and LC-MS/MS based untargeted metabolomics approach, rice roots of ZZY-1 and GD-6 colonized by S. indica, which were later treated with As (10 µM) and P (50 µM), were compared with non-colonized roots under the same treatments with a set of control plants. The responses of secondary metabolism related enzymes, especially polyphenol oxidase (PPO) activities in the foliage of ZZY-1 and GD-6 were enhanced 8.5 and 12-fold, respectively, compared to their respective control counterparts. The current study identified 360 cationic and 287 anionic metabolites in rice roots, and the commonly enriched pathway annotated by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was biosynthesis of phenylalanine, tyrosine and tryptophan, which validated the results of biochemical and gene expression analyses associated with secondary metabolic enzymes. Particularly under As+S.i+P comparison, both genotypes exhibited an upregulation of key detoxification and defense related metabolites, including fumaric acid, L-malic acid, choline, 3,4-dihydroxybenzoic acid, to name a few. The results of this study provided the novel insights into the promising role of exogenous P and S. indica in alleviating As stress.

Effects of CO2 enrichment by fermentation of CRAM on growth, yield and physiological traits of cherry tomato.

Carbon dioxide (CO2) concentration in greenhouses is sub-optimal for vegetable production. Many techniques have been used to increase CO2 concentration in greenhouses but most of them are expensive with certain limitations and drawbacks. We adopted a new strategy to elevate CO2 concentration in the greenhouse throughout the day via crop residues and animal manure composting (CRAM). During the whole cultivation period, CRAM-treated greenhouse had doubled CO2 concentration which significantly increased the yield of cherry tomatoes (Lycopersiconesculentum L.) i.e. up to 38%. The influence of CRAM procedure on cherry tomato quality was also investigated and the concentrations of total soluble solids (TSS) and soluble sugar were found to be significantly higher in cherry tomatoes grown under composting greenhouse than that of non-composting greenhouse. Additionally, CRAM-CO2 enrichment also resulted in increased concentrations of ascorbic acid (Vitamin C) and titrate acid as compared with the control. In contrast, the concentration of nitrate was considerably decreased in cherry tomato grown under CO2 enriched condition than that of control. The increase in active oxygen metabolisms such as POD, CAT and SOD while a decrease in MDA, as well as APX was observed for cherry tomatoes grown under CO2 enriched condition. Hence, CO2 fertilization by using CRAM in greenhouse significantly improved quality and increased the yield of cherry tomatoes.