Variations in leaf epicuticular n-alkanes in some Broussonetia, Ficus and Humulus species.

Abstract: n-Alkanes are biosynthesized from very long-chain fatty acid wax precursors and its distribution grants the most useful taxonomic contribution for plant species. In current study, five species from three genera of Moraceae family were sampled separately from three areas (Mountain Jin-yun, Mountain Jin-fo and Bei-bei) in Chongqing, China, namely, Broussonetia papyrifera, Broussonetia kazinoki, Ficus virens, Ficus tikoua, and Humulus scandens. The amounts of n-alkanes in epicuticular wax enabled discrimination among areas, varying from 4.9 μg cm−2 to 16.9 μg cm−2 in Mountain Jin-yun, 6.9 μg cm−2 to 20.5 μg cm−2 in Bei–bei, and 4.7 μg cm−2 to 61.7 μg cm−2 in Mountain Jin-fo, respectively. Among the five species, the amount of n-alkanes was the highest in B. papyrifera and the lowest in F. tikoua for all areas, showing high species variation. The most abundant n-alkanes in all investigated species were two odd-numbered n-alkanes, i.e., C29 and C31. The epicuticular waxes of H. scandens from Bei-bei had a higher relative abundance of C29 than other species from Mountain Jin-yun and Mountain Jin-fo. The chain length of n-alkanes from Bei-bei was longer than that from other areas. The even/odd predominance (EOP) or odd/even predominance (OEP) occurred in short-chain n-alkanes of plant epicuticular wax might be correlated with their growing environments. All Carbon Preference Index (CPIs) and Average Chain Length (ACLs) from Bei-bei were lower than those from other sampling areas, mainly attributing to the higher numbers of short- and mid-chain n-alkanes in plants from Bei-bei. Cluster analysis revealed that H. scandens from Bei-bei and F. virens from Mountain Jin-yun were different from other species. Based on these findings, it seems that environmental conditions contribute to the complex patterns and variation of n-alkanes and different plant species had different responses to environment changes. The distribution of n-alkanes could be a good indicator to distinguish plant species under different growing conditions before other obvious morphological changes could be observed. [Copyright &y& Elsevier]