Composition of Cuticular Waxes Coating Flag Leaf Blades and Peduncles of Triticum Aestivum Cv. Bethlehem

The work herein presents comprehensive analyses of the cuticular wax mixtures covering the flag leaf blade and peduncle of bread wheat (Triticum aestivum) cv. Bethlehem. Overall, Gas Chromatography-Mass Spectrometry and Flame Ionization Detection revealed a wax coverage of flag leaf blades (16 μg/cm(2)) a third that of peduncles (49 μg/cm(2)). Flag leaf blade wax was dominated by 1-alkanols, while peduncle wax contained primarily β-diketone and hydroxy-β-diketones, thus suggesting differential regulation of the acyl reduction and β-diketone biosynthetic pathways in the two analyzed organs. The characteristic chain length distributions of the various wax compound classes are discussed in light of their individual biosynthetic pathways and biosynthetic relationships between classes. Along with previously reported wheat wax compound classes (fatty acids, 1-alkanols, 1-alkanol esters, aldehydes, alkanes, β-diketone, hydroxy-β-diketones, alkylresorcinols and methyl alkylresorcinols), esters of 2-alkanols and three types of aromatic esters (benzyl, phenethyl and p-hydroxyphenethyl) are also reported. In particular, 2-heptanol esters were identified. Detailed analyses of the isomer distributions within 1-alkanol and 2-alkanol ester homologs revealed distinct patterns of esterified acids and alcohols, suggesting several wax ester synthases with very different substrate preferences in both wheat organs. Terpenoids, including two terpenoid esters, were present only in peduncle wax.