ABSTRACT
Grasses producing trans-aconitic acid, a geometric isomer of cis-aconitic acid, are often used in Glycine max rotation systems. However, the effects of trans-aconitic acid on Glycine max are unknown. We conducted a hydroponic experiment to evaluate the effects of 2.5-10â¯mM trans-aconitic acid on Glycine max growth and photosynthesis. The results revealed that the enhanced H2O2 production in the roots increased the membrane permeability and reduced the water uptake. These effects culminated with a reduced stomatal conductance (gs), which seems to be the main cause for a decreased photosynthetic rate (A). Due to low gs, the limited CO2 assimilation may have overexcited the photosystems, as indicated by the high production of H2O2 in leaves. After 96â¯h of incubation, and due to H2O2-induced damage to photosystems, a probable non-stomatal limitation for photosynthesis contributed to reducing A. This is corroborated by the significant decrease in the quantum yield of electron flow through photosystem II in vivo (ΦPSII) and the chlorophyll content. Taken together, the damage to the root system and photosynthetic apparatus caused by trans-aconitic acid significantly reduced the Glycine max plant growth.
Subject(s)
Aconitic Acid/pharmacology , Glycine max/growth & development , Photosynthesis/drug effects , Cell Membrane Permeability/drug effects , Chlorophyll/metabolism , Fluorescence , Gases/metabolism , Hydrogen Peroxide/metabolism , Plant Roots/drug effects , Plant Roots/metabolism , Plant Stomata/drug effects , Plant Stomata/physiology , Solutions , Glycine max/drug effectsABSTRACT
Velvet bean (Mucuna pruriens) is an efficient cover forage that controls weeds, pathogens and nematodes, and the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA) is its main allelochemical. The effects of 3 g L-1 of an aqueous extract of velvet bean seeds, along with 0.5 mM L-DOPA for comparison, were evaluated in roots, stems and leaves of soybean (Glycine max). The activities of phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) were determined, along with the lignin content and its monomeric composition. The results revealed similar effects caused by L-DOPA and the aqueous extract. Both treatments reduced PAL and CAD activities, lignin, and lignin monomer contents in roots; PAL and CAD activities in stems, and CAD activity in leaves. These findings provide further evidence that the effects of velvet bean cover forage on root lignification were due to the L-DOPA, its major allelochemical.
Subject(s)
Glycine max/metabolism , Mucuna/metabolism , Seeds/metabolism , Levodopa/metabolism , Lignin/metabolism , Phenylalanine Ammonia-Lyase/metabolism , Plant Roots/metabolism , Seeds/genetics , Glycine max/geneticsABSTRACT
The flavanone naringenin, an intermediate in flavonoid biosynthesis, was tested for its effect on root growth, phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, as well as phenolic compounds and lignin contents in soybean (Glycine max L. Merrill) seedlings. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), with or without 0.1 to 0.4 mM naringenin in a growth chamber (25°C, 12-h photoperiod, irradiance of 280 µmol m-2 s-1) for 24 h. Inhibitory effects on root growth (length, weight, cell viability), PAL and soluble POD activities were detected after naringenin treatments. These effects were associated with stimulatory activity of the cell wall-bound POD followed by an increase in the lignin contents, suggesting that naringenin-induced inhibition in soybean roots could be due to the lignification process.
Os efeitos de naringenina, um intermediário da biossíntese de flavonóides, foram avaliados sobre o crescimento das raízes, as atividades da fenilalanina amônia liase (PAL) e peroxidases, bem como sobre os teores de compostos fenólicos e de lignina em plântulas de soja (Glycine max L. Merrill). Plântulas de três dias foram cultivadas em solução nutritiva de Hoagland, meia-força (pH 6,0), contendo ou não, naringenina 0,1 a 0,4 mM, em uma câmara de germinação (25°C, fotoperíodo de 12 h, 280 µmol m-2 s-1) durante 24 h. Efeitos inibitórios no crescimento das raízes (comprimento, massa e viabilidade celular) e nas atividades da PAL e POD solúvel foram constatados após os tratamentos com naringenina. Estes efeitos foram associados com atividade estimulatória da POD ligada à parede celular, seguido por aumento nos teores de lignina, sugerindo que a inibição do crescimento das raízes pode ser devido ao processo de lignificação.
