Does silicon really matter for the photosynthetic machinery in plants ?

Silicon (Si) is known to alleviate the adverse impact of different abiotic and biotic stresses by different mechanisms including morphological, physiological, and genetic changes. Photosynthesis, one of the most important physiological processes in the plant is sensitive to different stress factors. Several studies have shown that Si ameliorates the stress effects on photosynthesis by protecting photosynthetic machinery and its function. In stressed plants, several photosynthesis-related processes including PSII maximum photochemical quantum yield (Fv/Fm), the yield of photosystem II (φPSII), electron transport rates (ETR), and photochemical quenching (qP) were observed to be regulated when supplemented with Si, which indicates that Si effectively protects the photosynthetic machinery. In addition, studies also suggested that Si is capable enough to maintain the uneven swelling, disintegrated, and missing thylakoid membranes caused during stress. Furthermore, several photosynthesis-related genes were also regulated by Si supplementation. Taking into account the key impact of Si on the evolutionarily conserved process of photosynthesis in plants, this review article is focused on the aspects of silicon and photosynthesis interrelationships during stress and signaling pathways. The assemblages of this discussion shall fulfill the lack of constructive literature related to the influence of Si on one of the most dynamic and important processes of plant life i.e. photosynthesis.

COVID-19 Prophylaxis Efforts Based on Natural Antiviral Plant Extracts and Their Compounds.

During the time of the novel coronavirus disease 2019 (COVID-19) pandemic, it has been crucial to search for novel antiviral drugs from plants and well as other natural sources as alternatives for prophylaxis. This work reviews the antiviral potential of plant extracts, and the results of previous research for the treatment and prophylaxis of coronavirus disease and previous kinds of representative coronaviruses group. Detailed descriptions of medicinal herbs and crops based on their origin native area, plant parts used, and their antiviral potentials have been conducted. The possible role of plant-derived natural antiviral compounds for the development of plant-based drugs against coronavirus has been described. To identify useful scientific trends, VOSviewer visualization of presented scientific data analysis was used.

Effect of Cold Stress on Photosynthetic Traits, Carbohydrates, Morphology, and Anatomy in Nine Cultivars of Stevia rebaudiana.

Stevia rebaudiana Bertoni is a sweet medicinal herb that is cultivated worldwide. This study aimed to identify the genotypic responses and function of nine cultivars of S. rebaudiana (accession numbers 1-9 from the EUSTAS Stevia Gene Bank) to low temperature. Plants were grown in vitro and incubated under controlled conditions at 5° or 25°C for 1 month. Cold stress significantly decreased the maximum quantum yield of photosystem II (Fv/Fm) in all cultivars, which was more pronounced in cultivars 5, 6, 8, and 9. The efficiency of photosystems I and II (PIABS) also declined in cold-stressed plants and was accompanied by reductions in net photosynthesis (PN), intercellular CO2 (Ci), water use efficiency (WUE), and chlorophyll a, chlorophyll b and carotenoid contents, more so in cultivars 5, 6, 8, and 9. Regardless of the downregulation of photosynthetic capacity, the cold stress increased water-soluble carbohydrates in all cultivars, which was accompanied by an increase in fresh leaf mass and area, more so in cultivars 5, 6, 8, and 9. Furthermore, cold stress increased the stomatal index and density, epidermal cell density, stem diameter, xylem vessel width, phloem tissue width, and number of sclerenchyma in all cultivars. Even though the nine cultivars of S. rebaudiana had lower PSII efficiencies at low temperatures, the increase in carbohydrates and leaf mass suggests that damage to PSII is not responsible for the reduction in its efficiency.