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Silicon enhances tolerance to abiotic and biotic stress

Wendy Zellner: University of Toledo

<div>Silicon (Si) is a plant nutrient critical for stress tolerance. Most of our knowledge regarding the uptake and function(s) of Si comes from studies with specific monocots that accumulate high foliar Si concentrations (1-10% Si dry weight). With this plant model system, Si has been shown to enhance defense as well as physically fortify cells for structural support. These physical responses are absent or reduced in plants, such as certain dicots, that accumulate less than 0.01% Si. Using tobacco, a low Si foliar accumulator, as a model system, <em>Tobacco Ringspot Virus</em> and copper (Cu) stress were shown to increase Si concentration in foliar tissue. Root Si concentrations were significantly higher than leaves, independent of the applied stress. Further studies indicated that root Si accumulation is not a significant source of soluble Si for leaves. In response to Cu, foliar accumulation in tobacco was obtained from media-absorbed Si at the time of stress, as opposed to mobilized root stores. These data suggest a regulated transport system within tobacco. In addition, studies with tobacco transporters, NtNIP2;1, NtPIP1;1 and NtRT-TIP1, resulted in permeability to Si in a <em>Xenopus</em> oocyte system. NtNIP2;1 was also shown to be Si-regulated. Low foliar accumulators provide the opportunity to more clearly understand Si-mediated defense, independent of physical fortification. Future research will focus on characterizing transporters involved in cellular movement of the element as well as document the alleviation of stress by Si.</div>

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