Silicon‐induced cadmium resistance in rice (Oryza sativa)

Abstract

Silicon (Si)‐induced cadmium (Cd) tolerance in rice (Oryza sativa L.) was investigated by analyzing Cd uptake, growth, and physiological parameters. Silicon treatments (0.0, 0.2, or 0.6 mM) were added to 6 d–old seedlings, and Cd treatments (0.0 or 5.0 μM) were added to 20 d–old seedlings. Parameters determined included: maximum net CO2 assimilation (Amax), stomatal conductance (gsmax), and transpiration (Emax) rates at varying intercellular CO2 concentrations (Ci). Also measured were chlorophyll fluorescence, growth, and Cd‐uptake parameters. Results showed a Si‐induced inhibition of Cd uptake. However, 0.2 mM or 0.6 mM Si treatment concentrations did not differentially inhibit Cd uptake or differentially alleviate Cd‐induced growth inhibition, despite a significant increase in tissue Si concentration due to 0.6 mM Si treatment compared to 0.2 mM Si treatment. Additionally, photosynthesis and chlorophyll‐fluorescence analysis showed that treatment with Cd significantly inhibited photosynthetic efficiency. Interestingly, the addition of 0.2 mM Si, more so than the addition of 0.6 mM Si, significantly alleviated the inhibitory effects of Cd toxicity on photosynthesis and chlorophyll‐fluorescence parameters. Our results suggest that 0.2 mM Si could be close to an optimum Si‐dose requirement for the alleviation of toxicity symptoms mediated by moderate (5 μM) Cd exposure.

Effects of Silicon on Alleviating Arsenic Toxicity in Maize Plants

“…An Si content greater than 1 % in the shoots characterizes the species as a accumulator of the element (Ma et al, 2001). Furthermore, greater Si accumulation in the shoots (leaves and stems) indicates that maize plants have a mechanism of active transport for this element, similar to rice (Nwugo and Huerta, 2008b).…”

Cadmium Toxicity in Plants and Role of Mineral Nutrients in Its Alleviation

“…Cd-induced inhibition of photosynthesis has also been attributed to an inhibition of the activity of key enzymes of the Calvin cycle and the photosynthetic electron transport chain in rice [30], and inhibition occurred at the uptake level or in translocation of nutrients. Cadmium may interfere with the nutrient uptake by altering the plasmamembrane permeability, leakage of nutrients through plasma membrane [31] and affect the element-transport processes across the membrane [32].…”

“…The potential of some of the important plant macro, micro and beneficial elements in alleviating Cd toxicity in plants is summarized below. Triticum aesitivum Increases ATP-S activity [5] Brassica juncea Increases GSH content [6,68] Ca Arabidopsis thaliana Decreases Cd content [77] Trifolium repens Decreases Cd accumulation [78] Mg Oryza sativa L. Decreases genes expression for Cd transport [80] Lupinus albus Protects photosynthetic tissues [86] Zn Triticum durum Addition of Zn to soil reduced crop Cd concentrations [95] Oryza sativa Inhibits Cd uptake [30] Brassica chinensis Suppresses Cd uptake and root-to-shoot transport [90] Arachis hypogaea Reduces shoot Cd accumulation and a stimulation of antioxidative enzymes [10] Se…”

“…The alleviation of the Cd-inhibitory effect on maize plants by Si was not due to exclusion of Cd from the plant, but due to increased cell-wall extensibility. Silicon promotes growth of rice plants through increasing cell wall extensibility and alleviates the low-level Cd toxicity by improving light-use-efficiency [30].…”

Review: The Functions of Phytoliths in Land Plants

“…in sodium hydroxide solution. Then a reducing mix including a colorant is added and finally the colouration of the solution is measured at a specific wavelength Nwugo and Huerta 2008). A sole standard method cannot be found.…”