Abstract
One of the characteristics of hyperhydric plants is the reduction of cell wall lignification (hypolignification), but how this is related to the observed abnormalities of hyperhydricity (HH), is still unclear. Lignin is hydrophobic, and we speculate that a reduction in lignin levels leads to more capillary action of the cell wall and consequently to more water in the apoplast. p-coumaric acid is the hydroxyl derivative of cinnamic acid and a precursor for lignin and flavonoids in higher plant. In the present study, we examined the role of lignin in the development of HH in Arabidopsis thaliana by checking the wild-types (Ler and Col-0) and mutants affected in phenylpropanoid biosynthesis, in the gene coding for cinnamate 4-hydroxylase, C4H (ref3-1 and ref3-3). Exogenously applied p-coumaric acid decreased the symptoms of HH in both wild-type and less-lignin mutants. Moreover, the results revealed that exogenously applied p-coumaric acid inhibited root growth and increased the total lignin content in both wild-type and less-lignin mutants. These effects appeared to diminish the symptoms of HH and suggest an important role for lignin in HH.
Highlights
Hyperhydricity (HH), refers to the abnormal growth that is observed in tissues grown in vitro in response to water availability from gelrite media, hormonal imbalance, and tissue culture conditions
The results indicated that the total lignin in the seedlings treated by piperonylic acid (PIP) significantly differed from those of the controls and that no significant difference was found with the less-lignin mutants
Our results showed that the possible influx of exogenously applied p-coumaric acid, a precursor for lignin, to Gelrite solidified medium, led to increases in total lignin that strengthen the cell wall and reduce root growth
Summary
Hyperhydricity (HH), refers to the abnormal growth that is observed in tissues grown in vitro in response to water availability from gelrite media, hormonal imbalance, and tissue culture conditions. Lignin plays several other important biological roles in plants Because it is much less hydrophilic than cellulose and hemicellulose, it prevents the absorption of water by these polysaccharides in plant cell to water, whereas lignin is more hydrophobic. Because it is much less hydrophilic than cellulose and hemicellulose, it prevents the absorption of water by these polysaccharides in plant cell walls and allows the efficient transport of water in the vascular tissues. The crosslinking of polysaccharides by lignin is an obstacle for water absorption i2notfo17the cell wall, allows for the efficient translocation of water and solutes over long distances within the vascular systems [11,12]
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