Abiotic and biotic stresses and changes in the lignin ... - ResearchGate

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Cd concentrations varying from 0.2 mM to 1 mM reduced the growth of soybean
roots and increased the lignin content (Bhuiyan et al., 2007). This was accompanied by
increased POD (cationic and anionic) activity, elevated laccase activity, and increased
expression of genes related to POD. The authors also noted that the laccases are
responsible for the biosynthesis of lignin during the initial stages of treatment with Cd
and that POD participation become important at later stages.
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Gases (CO 2 and Ozone)
It is expected that atmospheric concentrations of CO 2 will change from 360
μmol -1 to 550-1000 μmol -1 in the next 100 years. This will probably interfere with the
primary and secondary metabolism of plants (Davey et al., 2004).
With respect to secondary metabolism, it is known that high concentrations of
CO 2 interfere with the biosynthesis of lignin. But it has been observed both increases in
(Koricheva et al., 1998; Richard et al., 2001), reduction in (Knops et al., 2007) or even
no effect on the concentration of lignin (Cotrufo et al., 2005) with increasing rates of
CO 2 . Moreover, the response to high CO 2 concentrations is influenced by fertilization
with N (Matros et al., 2006). Accordingly, high concentrations of CO 2 in the roots of
Nicotiana tabacum cv. Samsun-NN grown in 5 mM of NH 4 NO 3 led to an increase in
lignin content; however, under 8 mM of NH 4 NO 3 , no changes in the levels of lignin
were observed (Matros et al., 2006).
Plantago maritima maintained for a year in an atmosphere of 600 μmol CO 2
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showed an increase in the biomass of stems and roots and changes in
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vascularization and lignification when compared with plants kept in normal
concentrations of CO 2 (Davey et al., 2004). An atmosphere rich in CO 2 resulted in a