Changes in cell wall composition and esterification patterns in response to drought stress
In order to investigate the potential source(s) of MeOH and AA emissions from poplar leaves and evaluate potential impacts of drought stress on the cell wall polysaccharide composition, leaf bulk monosaccharide composition was determined from AIR samples. Consistent with the expected high pectin content of rapidly expanding leaf primary cell walls, monosaccharide content of AIR from control poplar leaves was dominated by galacturonic acid (GalA, Figure 10a ). While the monosaccharide content, and by extension polysaccharide content of the cell walls remained largely unchanged during drought, we observed an increase in O -acetyl ester content during drought (Figure 10b ). AIR from control leaves released an average of 0.69 µg g-1 of free acetate following saponification which increased by 10% to 0.76 µg g-1 of free acetate g-1 from drought stressed leaves. Leaf AIRO -acetyl ester content increased throughout the drought, reaching a maximum after 7 days (Figure 10b ). After 7 days, the leaves were fully desiccated, and subsequently detached from the tree.