Pesticide effects on secondary metabolism of higher plants

Abstract

Secondary compounds serve both endogenous and exogenous functions in higher plants because they are involved in plant growth and development as well as intraspecies and interspecies interactions. Documentation of the effects of pesticides on secondary compound biosynthesis in higher plants is increasing. While several herbicides have been reported to reduce levels of secondary compounds by non‐specific mechanisms, a few herbicides, such as alachlor and glyphosate, directly affect specific biosynthetic steps. Alachlor reduces flavonoid synthesis at a step late in the biosynthetic pathway, and glyphosate blocks synthesis of all cinnamate derivatives by inhibiting 5‐enolpyruvyl shikimate‐3‐phosphate (EPSP) synthase. Inhibition of EPSP synthase also leads to the accumulation of high levels of shikimate, benzoic acids and benzoic acid derivatives. The sulfonylureas and p‐nitro‐substituted diphenylether (DPE) herbicides can cause increases in the level of cinnamatederived phenolic compounds and the DPEs can cause dramatic increases in terpenoid stress metabolites. Certain fungicides are thought to act through enhancing the capacity of plants to produce phytoalexins. These and other data suggest that sublethal effects of pesticides on target and non‐target plants can significantly affect agricultural ecosystems by altering the synthesis of compounds important in inter‐ and intraspecies interactions.

Aplicação foliar de manganês em soja transgênica tolerante ao glyphosate

“…Na soja Roundup Ready, o glyphosate é aplicado em pós-emergência durante a fase vegetativa da cultura, absorvido e translocado nas plantas, promovendo eficiente controle das plantas daninhas em um estádio em que essa competição seria extremamente prejudicial à cultura comercial. Embora o glyphosate seja eficiente no controle de plantas daninhas, existem relatos por parte de alguns pesquisadores dos diferentes efeitos fisiológicos induzidos por esse herbicida (LYDON & DUKE, 1989).…”

Selected Phenolic Compounds in Cultivated Plants: Ecologic Functions, Health Implications, and Modulation by Pesticides

“…Other herbicides have more specific effects. Glyphosate blocks the shikimate pathway, thereby reducing the synthesis of aromatic amino acids (phenylalanine, tyrosine, tryptophan) and causing an accumulation of shikimate (52,53). Gallic acids, which are components of hydrolyzable tannins, are mainly synthesized from shikimate.…”

“…Possibly as a protective reaction to the oxidative damages, plants increase the PAL synthesis and synthesize more flavonoids. For example, xanthotoxin content in celery is increased after the application of acifluorfen ( (52,53) amide, and carbamate classes) are able to reduce the PAL synthesis in soy seedlings (54). Some fungicides can also modulate concentrations of secondary compounds.…”

“…Maneb, benomyl, and nabam induced the synthesis of hydroxyphaseollin in soy (53). The effect of insecticides on plant phenolics was not extensively investigated (52). Methomyl modulates the contents of tannin in cotton (52).…”

Glyphosate e associações em pós-emergência no desempenho agronômico e na qualidade das sementes de soja RR®

“…(Padgette et al, 1995), a qual é insensível ao glyphosate. Contudo, podem ocorrer problemas no metabolismo secundário (Lydon & Duke, 1989), na produção de fitoalexinas (Keen et al, 1982), na rizosfera (Kremer et al, 2005), na fixação biológica do nitrogênio (Zablotowicz & Reddy, 2004;María et al, 2006;Dvoranen et al, 2008), na nutrição mineral (Neumann et al, 2006;Zobiole et al, 2010a,b), na fotossíntese, uso da água e formação de biomassa (Zobiole et al, 2010c), na composição química das sementes (Zobiole et al 2010d), no conteúdo de lignina e produção de aminoácidos (Zobiole et al, 2010e) e na produção de metabólitos com potencial de injúria (Reddy et al, 2004).…”