Elevated CO2 reduces vessel diameter and lignin deposition in some legume plants grown in mini-FACE rings

Abstract

Studies on stem (and leaf) structure and histology of a semi-natural grassland community, permanently growing in mini-FACE rings under elevated concentrations of atmospheric CO2 (560 μmol mol-1) are presented. Histochemical analysis of stem sections from legume plants grown under high CO2 concentration revealed both a reduction of lignin deposition in spring vascular bundles of Trifolium repens L., and a decrease in size of the xylem vessels in Vicia hybrida L. and Vicia sativa L. Thus, the effects of elevated CO2 on the stem histology of the species investigated are rather species-specific and/or organ-specific, and of major account especially in the early phases of vegetative growth, in particular as regards lignin deposition mechanisms. In leaves, neither differences as to lignification nor any other anatomical structure modification were found under CO2 enrichment.