Silicon potentiates host defense mechanisms against infection by plant pathogens

Document Type

Article

Publication Date

1-1-2015

Abstract

Several agronomic and horticultural crops, such as barley, cucumbers, oats, rice, sugarcane, and wheat, benefi t from applications of silicon. Growth enhancements results, in part, from reductions in the intensities of plant diseases. For the rice- Pyricularia oryzae model pathosystem, the mechanical barrier formed from silicon polymerization below the cuticle and in the cell walls was the fi rst proposed hypothesis to explain how this element reduced the number of blast lesions and the lesion sizes. However, new insights have revealed that silicon's effect on plant resistance to a number of diseases may also occur through mediated host plant resistance mechanisms against pathogen infection. Plants supplied with silicon exhibit potentiated activation of the phenylpropanoid pathway resulting in increases in total soluble phenolics and lignin. The activities of defense enzymes, such as chitinases and â -1,3-glucanases, are maintained at higher levels during infection and the transcription of defense related genes occur faster and with greater output. When plants are supplied with silicon and then challenged with a pathogen, there is an enhanced activation in antioxidant metabolism, which in turn, suppresses the damaging cytotoxic effect of the reactive oxygen species that causes lipid peroxidation in the cell membrane. At the physiological level, leaf gas exchange parameters of silicon-treated plants are higher upon pathogen infection for crops, such as common beans, rice, sorghum and wheat, indicating the ameliorating effect of this element on photosynthesis. Although our understanding of how silicon affects plants in response to infection has advanced, the exact mechanism(s) by which siliconmodulates plant physiology through the potentiation of host defense mechanisms still requires further investigation at the genomics, proteomics, and metabolomics levels.

Publication Source (Journal or Book title)

Silicon and Plant Diseases

First Page

109

Last Page

138

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