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The application of biochar to traditional soil and soilless growth media in agriculture has been reported to increase plant production. However, it remains unclear which biochar component drives this process or which biogeochemical process is attributed to better plant productivity. Therefore, this study aims to determine how biochar organic carbon (C) composition and thermal stability influence nitrogen availability and tomato production. Soilless growth media composed of a mixture of 60% and 40% coconut coir (CC) (Cocos nucifera L.) and fine pine bark (PB) (Pinus genus), respectively, was amended with 0, 1, 2, 3, 4, 6, 8, 10, and 12% biochar per dry weight. The amended media were used to grow Red Bounty tomatoes (Lycopersicum esculentum) for three months. After harvesting tomatoes and determining yield, organic C composition and C thermal stability of the biochar amended soilless growth media mixtures were determined using solid-state 13C nuclear magnetic resonance (13C NMR) and multi-elemental scanning thermal analysis (MESTA), respectively. Thermal stability data were used to determine the “R400 index”, and nitrate (NO3−) concentration was determined using the water extractable method. Results showed that biochar-amended media significantly increased pH (p < 0.0001) and NO3− (p = 0.0386) compared to the no-char control. Biochar amended soilless media organic C composition was dominated by O-alkyl-C as a result of a higher fraction of soilless media; however, total C, carboxyl-C, phenolic-C, and aromatic-C increased with increasing biochar content and related negatively to R400, which decreased with increasing biochar content. Nitrate retention and tomato yield increased with increasing total C, carboxyl-C, phenolic-C, and aromatic-C and decreasing R400. This indicates that the stable form of C, carboxyl-C, phenolic-C, aromatic-C, and low R400 enhanced NO3− sorption, reducing leaching and enhancing its availability for tomato growth.

Like other plant stresses, salinity is a central agricultural problem, mainly in arid or semi-arid regions. Therefore, salt-adapted plants have evolved several adaptation strategies to counteract salt-related events, such as photosynthesis inhibition, metabolic toxicity, and reactive oxygen species (ROS) formation. European grapes are usually grafted onto salt-tolerant rootstocks as a cultivation practice to alleviate salinity-dependent damage. In the current study, two grape rootstocks, 140 Ruggeri (RUG) and Millardet et de Grasset 420A (MGT), were utilized to evaluate the diversity of their salinity adaptation strategies. The results showed that RUG is able to maintain higher levels of the photosynthetic pigments (Chl-T, Chl-a, and Chl-b) under salt stress, and hence accumulates higher levels of total soluble sugars (TSS), monosaccharides, and disaccharides compared with the MGT rootstock. Moreover, it was revealed that the RUG rootstock maintains and/or increases the enzymatic activities of catalase, GPX, and SOD under salinity, giving it a more efficient ROS detoxification machinery under stress.

Salinity is one of the substantial threats to plant productivity and could be escorted by other stresses such as heat and drought. It impairs critical biological processes, such as photosynthesis, energy, and water/nutrient acquisition, ultimately leading to cell death when stress intensity becomes uncured. Therefore, plants deploy several proper processes to overcome such hostile circumstances. Grapevine is one of the most important crops worldwide that is relatively salt-tolerant and preferentially cultivated in hot and semi-arid areas. One of the most applicable strategies for sustainable viticulture is using salt-tolerant rootstock such as Ruggeri (RUG). The rootstock showed efficient capacity of photosynthesis, ROS detoxification, and carbohydrate accumulation under salinity. The current study utilized the transcriptome profiling approach to identify the molecular events of RUG throughout a regime of salt stress followed by a recovery procedure. The data showed progressive changes in the transcriptome profiling throughout salinity, underpinning the involvement of a large number of genes in transcriptional reprogramming during stress. Our results established a considerable enrichment of the biological process GO-terms related to salinity adaptation, such as signaling, hormones, photosynthesis, carbohydrates, and ROS homeostasis. Among the battery of molecular/cellular responses launched upon salinity, ROS homeostasis plays the central role of salt adaptation.

The influence of biostimulation using dissolved organic carbon (DOC) on rhizodegradation of perchlorate and plant uptake was studied under greenhouse conditions using soil and hydroponic bioreactors. One set of bioreactors planted with willow (Salix babylonica) plants was spiked with 300 mg L −1 DOC in the form of chicken manure extract, whereas a second set was not treated with DOC. A similar experiment without willow plants was run in parallel to the planted bioreactors. The planted soil bioreactors amended with DOC reduced perchlorate from 65.85 to 2.67 mg L −1 in 21 days for humic soil (95.95% removal) and from 68.99 to 0.06 mg L − 1 for sandy loam (99.91% removal) in 11 days. Nonplanted DOC treated soil bioreactors achieved complete perchlorate removal in 6 and 8 days for humic and sandy loam, respectively. Both planted and nonplanted soil bioreactors without DOC removed > 95% perchlorate within 8 days. Planted soil bioreactors respiked with perchlorate reduced perchlorate to nondetectable levels in 6 days. Hydroponics experiment amended with DOC reduced perchlorate from approximately 100 mg L − 1 to nondetectable levels within 7 to 9 days. Hydroponic bioreactors without DOC had low perchlorate removal rates, achieving 30% removal in 42 days. Leaf samples from sandy loam soil bioreactors without DOC had four times perchlorate phytoaccumulation than the DOC-treated plants. Similar results were obtained with the nonplanted bioreactors. Persistence of perchlorate in solution of planted hydroponic bioreactors without DOC amendment suggested that natural DOC from the plant exudates was not enough to biostimulate perchlorate reducing microbes. The hydroponic bioreactor study provided evidence that DOC is a limiting factor in the rhizodegradation of perchlorate.

In an effort to expand the technology of bioremediation of hydrophobic organic compounds, microencapsulation technology was investigated as a method of biosurfactant delivery to contaminated sites. Microparticles are composed of active or inactive materials encapsulated in a polymer coating designed for controlled release of the encapsulated substance. Surface morphology and release profiles of microparticles containing rhamnolipid biosurfactant were investigated for development of a controlled release bioremediation scheme. The evaluation was conducted under laboratory conditions with 45 mg/ml concentration of biosurfactant and a representative environmental medium; using artificial salt water (35 ppt) and deionized water medium as a control. The microparticles were prepared by the water-in-oil-in-water double emulsion solvent evaporation method. The surface morphology was examined after initial preparation, at 0, 15 and 31 days incubation, using light microscopy. Light microscopic images revealed smooth, spherical microparticles that degraded over time in the media. Results indicated that microparticle degradation occurred mostly in the salt water environment, suggesting that the presence of salts (Na + and Cl − ions) in the water enhanced microparticle degradation. The deionized water environment achieved polymeric degradation that was similar to what was generally reported in the literature. Biosurfactant release was evaluated for polymer molecular weights (M w ) 40, 80, and 200 kDa, in salt water and deionized water media, each of which showed a high initial burst release of biosurfactant, followed by pulse releases that occurred over the 31 day period. The highest level of biosurfactant release of all the molecular weights tested occurred in the M w 80 kDa. The release from M w 40 kDa and M w 200 kDa was not significantly different (P > 0.05). The results showed that this technology may be useful for enhancing bioremediation of residual hydrophobic organic contaminants (HOC) in estuarine and marine environments.