Exploration of silicon functions to integrate with biotic stress tolerance and crop improvement

In the era of climate change, due to increased incidences of a wide range of various environmental stresses, especially biotic and abiotic stresses around the globe, the performance of plants can be affected by these stresses. After oxygen, silicon (Si) is the second most abundant element in the earth's crust. It is not considered as an important element, but can be thought of as a multi-beneficial quasi-essential element for plants. This review on silicon presents an overview of the versatile role of this element in a variety of plants. Plants absorb silicon through roots from the rhizospheric soil in the form of silicic or monosilicic acid. Silicon plays a key metabolic function in living organisms due to its relative abundance in the atmosphere. Plants with higher content of silicon in shoot or root are very few prone to attack by pests, and exhibit increased stress resistance. However, the more remarkable impact of silicon is the decrease in the number of seed intensities/soil-borne and foliar diseases of major plant varieties that are infected by biotrophic, hemi-biotrophic and necrotrophic pathogens. The amelioration in disease symptoms are due to the effect of silicon on a some factors involved in providing host resistance namely, duration of incubation, size, shape and number of lesions. The formation of a mechanical barrier beneath the cuticle and in the cell walls by the polymerization of silicon was first proposed as to how this element decreases plant disease severity. The current understanding of how this element enhances resistance in plants subjected to biotic stress, the exact functions and mechanisms by which it modulates plant biology by potentiating the host defence mechanism needs to be studied using genomics, metabolomics and proteomics. The role of silicon in helping the plants in adaption to biotic stress has been discussed which will help to plan in a systematic way the development of more sustainable agriculture for food security and safety in the future.

Insights into the microbial community structure of anaerobic digestion of municipal solid waste landfill leachate for methane production by adaptive thermophilic granular sludge

BACKGROUND: The amount of municipal solid waste (MSW) gradually increased along with the rapid development of modern cities. A large amount of landfill leachate are generated with excessive chemical oxygen demand (COD), which create a great deal of pressure on the environment-friendly treatment process. Anaerobic digestion is an ideal technique to solve the above problem. RESULTS: A thermophilic granular sludge was successfully adapted for anaerobic digestion of MSW leachate (from an aging large-scale landfill) for methane production. The COD degradation efficiency improved by 81.8%, while the methane production rate reached 117.3 mL CH4/(g VS d), which was 2.34-fold more than the control condition. The bacterial and archaeal communities involved in the process were revealed by 16S rRNA gene high-throughput pyrosequencing. The richness of the bacterial community decreased in the process of thermophilic granular sludge, while the archaeal community structure presented a reverse phenomenon. The bacterial genus, Methanosaeta was the most abundant during the mesophilic process, while Methanobacterium, Methanoculleus, Methanosaeta and Methanosarcina were more evenly distributed. The more balanced community distribution between hydrogenotrophic and acetotrophic methanogens implied a closer interaction between the microbes, which further contributed to higher methane productivity. The detailed relationship between the key functional communities and anaerobic digestion performances were demonstrated via the multivariate canonical correspondence analysis. Conclusions: With the assistance of adaptive thermophilic granular sludge, microbial community structure was more evenly distributed, while both of COD degradation rate and methane production was improved during anaerobic digestion of MSW landfill leachate.

Optimized Ultrasonic-Assisted Extraction of Polysaccharides from Chinese Traditional Medicinal Plant Paris fargesii Using Orthogonal Design.

Paris fargesii is a famous Chinese traditional medicinal plant used as antipyretic, antidotal, antiphlogistic and analgesic. This research aimed at the determination of the total polysaccharides contents in P. fargesii, which were collected from Baoxing country of Sichuan Province in order to get the optimized extraction technology. Ultrasonic method was adopted in the extraction of total polysaccharides from P. fargesii. Through single factor experiment and orthogonal test, the effects of ultrasonic extraction conditions on the total polysaccharides extraction were measured, including solid-liquid ratio, ultrasonic temperature, ultrasonic power and ultrasonic time. Then colorimetric method was applied for the assaying. The optimized extraction conditions of total polysaccharides from P. fargesii were as follows: ultrasonic power: 600w, solid-liquid ratio: 1:20, ultrasonic extraction time: 1.5h and ultrasonic temperature: 90℃. Under the optimum parameters, the total polysaccharides extraction efficiency was 0.0715%.