Trans-aconitic acid inhibits the growth and photosynthesis of Glycine max

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 2.5-10 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 (g_s), which seems to be the main cause for a decreased photosynthetic rate (A). Due to low g_s, the limited CO₂ assimilation may have overexcited the photosystems, as indicated by the high production of H₂O₂ in leaves. After 96 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 (Φ_PSII) 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.

Keywords: Chlorophyll a fluorescence; Gas exchange; Photosynthetic rate; Reactive oxygen species.