Abstract
Background: CPO refining which produces solid waste namely spent bleaching earth (SBE) in large quantities can pollute the environment. SBE from bentonite ores contains large amounts of silica, so it can be an alternative source of silica minerals. Silica plays an important role in increasing plant resistance and bioactive plant compound products. Methods: The application of Si in plants can increase secondary metabolites such as phenolic and anti-fungal compounds in response to disease pathogens. However, the low solubility of silica makes silica not sufficiently available for plants. Using microorganisms as silica solubilizing bacteria helps increasing solubility of silica in the soil. Bacteria dissolve silica by removing organic acids and producing indole acetic acid (AAI), which stimulates root hairs. Results: This review presents the results of a study on the utilization of silica-rich SBE waste as a source of available silica for plants with solubilizing method using bacteria to increase plant growth and resistance, as well as increase plant secondary metabolite compounds. Conclusions: The application of silica solubilizing bacteria has been known to play an important role in providing silica for plants, through enzymatic mechanisms, namely the production of organic acids and extracellular polysaccharides.
Highlights
One of the essential nutrients for plants is silica (Si), known as the beneficial element for rice plants (Epstein, 1999)
This review presents the results of a study on the utilization of silica-rich Spent Bleaching Earth (SBE) waste as a source of available silica to plants
Silica is polymerized within epidermal cells, strengthening plant cell membranes, maintaining water potential, and preventing electrolyte leakage (Agarie et al 1998)
Summary
One of the essential nutrients for plants is silica (Si), known as the beneficial element for rice plants (Epstein, 1999). Si's function in plants is to aid cell walls, prevent pests and pathogens, reduce water loss by evapotranspiration, and reduce heavy metals' toxicity and elements essential for normal development in some species (Savant et al, 1999). The availability of silica in the soil is a need for plants to deal with the growth period. Silica administration can increase phosphorus (P) availability and reduce the activity of Al, Fe, and Mn (Yukamgo & Yawono, 2007). Lack of nutrients Si can reduce the optimum productivity of plants because silica has an essential role in increasing plant resistance. The beneficial effects of the si are usually clearly indicated when the plant is under stress
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