Pyroligneous acid (PA) is a reddish-brown liquid obtained through the condensation of smoke formed during biochar production. PA contains bioactive compounds that can be utilized in agriculture to improve plant productivity and quality of edible parts. In this study, we investigated the biostimulatory effect of varying concentrations of PA (i.e., 0%, 0.25%, 0.5%, 1%, and 2% PA/ddH2O (v/v)) application on tomato (Solanum lycopersicum ‘Scotia’) plant growth and fruit quality under greenhouse conditions. Plants treated with 0.25% PA exhibited a significantly (p < 0.001) higher sub-stomatal CO2 concentration and a comparable leaf transpiration rate and stomatal conductance. The total number of fruits was significantly (p < 0.005) increased by approximately 65.6% and 34.4% following the application of 0.5% and 0.25% PA, respectively, compared to the control. The 0.5% PA enhanced the total weight of fruits by approximately 25.5%, while the 0.25% PA increased the elemental composition of the fruits. However, the highest PA concentration of 2% significantly (p > 0.05) reduced plant growth and yield, but significantly (p < 0.001) enhanced tomato fruit juice Brix, electrical conductivity, total dissolved solids, and titratable acidity. Additionally, total phenolic and flavonoid contents were significantly (p < 0.001) increased by the 2% PA. However, the highest carotenoid content was obtained with the 0.5% and 1% PA treatments. Additionally, PA treatment of the tomato plants resulted in a significantly (p < 0.001) high total ascorbate content, but reduced fruit peroxidase activity compared to the control. These indicate that PA can potentially be used as a biostimulant for a higher yield and nutritional quality of tomato.

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Background Pyroligneous acid (PA) is an aqueous smoky fraction produced during pyrolysis of biomass. The chemical composition of PA from different plant biomass has been studied, but reports on PA metabolites and elemental profiles are rare. In this study, we examined the metabolites, elemental profiles and the associated chemical activities of PA derived from white pine (Pinus strobus) at 1100 °C compared to similar work done elsewhere using different biomass at lower temperatures. Results PA from P. strobus biomass exhibited a lower electrical conductivity (2.05 mS/cm), salinity (1.03 g/L) and total dissolved solids (1.42 g/L) but higher oBrix content (9.35 ± 0.06) compared to PA from other feedstock. The P. strobus PA showed a higher antioxidant activity characterized by enhanced radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl free-radical (78.52%) and accumulation of higher total phenolic (95.81 ± 1.45 gallic acid equivalents (GAE)/mL) and flavonoid content (49.46 µg quercetin/mL). Metabolite profiling by direct injection mass spectrometry with a reverse-phase liquid chromatography–mass spectrometry (DI/LC–MS/MS) identified a total of 156 metabolites. Four (4) main groups including organic acids (90.87%), hexose (8.60%), carnitine (0.3%) and phospholipids (0.24%) were found in the PA. Mineral element analysis revealed that the P. strobus PA contained high concentrations of nitrogen (N), potassium (K), calcium (Ca) and zinc (Zn), while the content of sodium (Na) and trace/heavy metals were present at levels below the reported limit. Conclusion This study indicates that P. strobus PA is a valuable product that can be used in agriculture to improve plant growth and productivity under normal and environmentally stressful conditions. Graphical Abstract

Heterotrimeric G-proteins are complexes that regulate important signalling pathways essential for growth and development in both plants and animals. Although plant cells are composed of the core components (Ga, Gb and Gc subunits) found in animal G-proteins, the complexities of the architecture, function and signalling mechanisms of those in animals are dissimilar to those identified in some plants. Current studies on plant G-proteins have improved knowledge of the essential physiological and agronomic properties, which when harnessed, could potentially impact global food security. Extensive studies on the molecular mechanisms underlying these properties in diverse plant species will be imperative in improving our current understanding of G-protein signalling pathways involved in plant growth and development. The advancement of G-protein signalling networks in distinct plant species could significantly aid in better crop development. This review summarizes current progress, novel discoveries and future prospects for this area in potential crop improvement.

Aluminum (Al) is the third most ubiquitous metal in the earth’s crust. A decrease in soil pH below 5 increases its solubility and availability. However, its impact on plants depends largely on concentration, exposure time, plant species, developmental age, and growing conditions. Although Al can be beneficial to plants by stimulating growth and mitigating biotic and abiotic stresses, it remains unknown how Al mediates these effects since its biological significance in cellular systems is still unidentified. Al is considered a major limiting factor restricting plant growth and productivity in acidic soils. It instigates a series of phytotoxic symptoms in several Al-sensitive crops with inhibition of root growth and restriction of water and nutrient uptake as the obvious symptoms. This review explores advances in Al benefits, toxicity and tolerance mechanisms employed by plants on acidic soils. These insights will provide directions and future prospects for potential crop improvement.

Municipal solid waste (MSW) compost is used to enrich soils by virtue of its bio-physicochemical properties. But undesirable accumulation of chemical elements can reduce soil quality and cause food safety issues. A 5-year field study was carried out to investigate the impact of Compost Quality Alliance tested MSW compost application frequency (annual, biennial and no-compost) on soil quality and chemical elements accumulation in edible portions of lettuce (Lactuca sativa cv. Grand Rapids), beets (Beta vulgaris cv. Detroit Supreme), carrot (Daucus carota cv. Nantes) and green bean (Phaseolus vulgaris cv. Golden Wax). Analysis of soil showed that chemical elements were highest in annual followed by biennial, but less in control (no-compost) and fallow soils. Soil background levels of chemical elements influenced the concentrations of iron and manganese in green bean, aluminum in green bean and beets, and barium in carrot, beets, and lettuce. Cadmium concentration in beets, lettuce, and green bean grown in annual plot was increased by 48%, 52% and 62%, respectively while carrot recorded 56% increase in the biennial plot compared to no-compost. Bioaccumulation factors < 1 for all the essential and non-essential trace elements in all the plant species except boron and molybdenum. However, lettuce showed a higher tendency to accumulate cadmium, rubidium, and strontium. Overall, the health risk for human consumption is low. Although long-term annual application of compost to vegetables seemed safe for human consumption, it is necessary to continuously monitor potential chemical elements accumulation, particularly non-essential trace elements in soils and plants.

A combination of vermicast and sawdust mixed medium is commonly used in horticulture, but the added benefit of microbial inoculation and mechanism of nutrient availability are unknown. This study was done to determine nutrient mineralization and nutrient release patterns of different combinations or a mix of vermicast-sawdust growing media amended with or without Trichoderma viride (105 spores/g). The mixed-media treatments were (1) 80% vermicast+20% sawdust; (2) 60% vermicast+40% sawdust; (3) 40% vermicast+60% sawdust; (4) 20% vermicast+80% sawdust; and (5) sawdust alone (control). Total dissolved solids, electric conductivity and salinity increased with each sampling time following submergence in deionized. Nutrients released from media without T. viride were significantly higher than the corresponding media with added T. viride. Overall, the starting total nitrogen of the different media did not change during the incubation period, but nitrate-nitrogen was reduced to a negligible amount by the end of day 30 of incubation. A repeated measures analysis showed a significant effect of Time*T. viride*Treatment on total dissolved solids. Redundancy analysis demonstrated a positive and strong association between media composed of ≥40% vermicast and ≤60% sawdust with or without T. viride and mineral nutrients released, electrical conductivity, total dissolved solids and salinity. These findings suggest that fast-growing plants may benefit from 40% to 60% vermicast added to 40% to 60% sawdust without T. viride while slow-growing plants can benefit from the same mixed medium combined with the addition of T. viride. Further investigation is underway to assess microbial dynamics in the mixed media and their influence on plant growth.

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