Atmospheric pCO 2 impacts leaf structural and physiological traits in Quercus petraea seedlings

Atmospheric p CO impacts Quercus petraea biomass production and cell wall composition of the leaves in favor of cellulose at the expense of lignin, and enhances foliar non-structural carbohydrate levels and sucrose contents in a pCO concentration-dependent manner. Sessile oak (Quercus petraea Liebl.) was grown for ca. half a year from seeds at ambient control (525 ppm), 750, 900, and 1000 ppm atmospheric pCO under controlled conditions. Increasing pCO enhanced biomass production, modified the cell wall composition of the leaves in favor of cellulose at the expense of lignin, and enhanced the foliar non-structural carbohydrate level, in particular the sucrose content; as well as total N content of leaves by increased levels of all major N fractions, i.e., soluble proteins, total amino acids, and structural N. The enhanced total amino acid level was largely due to 2-ketoglutarate and oxalo acetate-derived compounds. Increasing pCO alleviated oxidative stress in the leaves as indicated by reduced H O contents. High in vitro glutathione reductase activity at reduced H O contents suggests enhanced ROS scavenging, but increased lipid peroxidation may also have contributed, as indicated by a negative correlation between malone dialdehyde and H O contents. Almost all these effects were at least partially reversed, when pCO exceeded 750 or 900 ppm. Apparently, the interaction of atmospheric pCO with leaf structural and physiological traits of Q. petraea seedlings is characterized by a dynamic response depending on the pCO level.