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

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 HO production in the roots increased the membrane permeability and reduced the water uptake. These effects culminated with a reduced stomatal conductance (g), which seems to be the main cause for a decreased photosynthetic rate (A). Due to low g, the limited CO assimilation may have overexcited the photosystems, as indicated by the high production of HO in leaves. After 96 h of incubation, and due to HO-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) 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.