Figure 8.

2D-HSQC NMR spectra of stems from three olive cultivars (Giarraffa, Leccino, and Maurino) subjected to drought stress (DS) (bottom) and their corresponding stem controls (top). The primary lignin structures identified are also shown. A: β-O-4′ alkyl-aryl ethers; B: β-5′ phenylcoumarans; C: β-β′ resinols; F: β-1′-spirodienones Cinnamyl alcohol end-groups (I), cinnamaldehyde end-groups (J), p-hydroxyphenyl units (H), guaiacyl units (G), syringyl units (S), and Cα-oxidized syringyl units (Sʹ). The yellow boxes reflect semi-quantitative estimates of lignin units and compounds. Composition is expressed in molar percent (H + G + S = 100%), and end-groups are expressed as a fraction of the total lignin inter-unit linkage types A–F.