Effects of elevated CO2 concentration on leaves and berries of black elder (Sambucus nigra) using UHPLC-ESI-QTOF-MS/MS and gas exchange measurements.

The effect of elevated CO₂ concentration on leaves of black elder (Sambucus nigra) was investigated based on leaf gas exchange, chlorophyll content as well as on the analysis of the underlying metabolite profile of the fruits. The measurements were carried out once a month over a period of time of 4 months. The CO₂ uptake rate, the transpiration rate and stomatal conductance were significantly higher in plants under ambient CO₂, in comparison to plants grown under elevated CO₂ concentrations. On the other hand, at the initial phase of the experiments, the photosynthesis rate was higher in CO₂ loaded plants compared to plants grown under normal conditions. Remarkably, after about one month a habituation effect could be observed leading to a decrease of the photosynthetic efficiency approaching again the normal level. To understand the observed effects on a molecular level, non-targeted fingerprinting analysis was performed on the ripe elder berries using LC-qToF-ESI-MS(/MS). Differences in the composition of various phenols, triglycerides and PC (36:5) as well as a stigmasterole-derivate could be detected. In contrast, central metabolic pathways such as photosynthesis, the tricarboxylic acid cycle as well as the biosynthesis of essential amino acids obviously are not considerably affected.