Variability in C₃-plant cell-wall biosynthesis in a high-CO ₂ atmosphere by solid-state NMR spectroscopy

We have used a frequency-selective rotational-echo double-resonance (REDOR) solid-state NMR experiment to measure the concentrations of glycine-glycine pairs in proteins (and protein precursors) of intact leaves of plants exposed to both high- and low-CO₂ atomospheres. The results are interpreted in terms of differences in cell-wall biosynthesis between plant species. We illustrate this variability by comparing the assimilation of label in cheatgrass and soybean leaves labeled using ¹⁵N-fertilizer and ¹³CO₂ atmospheres. Cheatgrass and soybean are both C ₃ plants but differ in their response to a high-CO₂ environment. Based on REDOR results, we determined that cheatgrass (a plant that seems likely to flourish in future low-water, high-CO₂ environments) routes 2% of the assimilated carbon label that remains in the leaf after 1 h in a 600-ppm ¹³CO₂ atmosphere to glycine-rich protein (or its precursors), a structural component of cell walls cross-linked to lignins. In contrast, soybean under the same conditions routes none of its assimilated carbon to glycine-rich protein.