Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017, Lisboa, Portugal.
Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017, Lisboa, Portugal.
Phytochemistry. 2021 Jan;181:112570. doi: 10.1016/j.phytochem.2020.112570. Epub 2020 Nov 6.
The cutin content and composition of cork oak (Quercus suber) leaves was determined in six provenances with different seed geographical origin spreading across the species natural distribution. The cutin layer on the leaf surface was on average 518 μg/cm of leaf area and represented 6.7% of the leaf dry weight, with no significant differences among provenances. Cutin depolymerisation was carried out by transesterification on whole leaves. The cutin composition of cork oak leaves is presented here for the first time. It is essentially composed of long-chain aliphatic ω-hydroxy fatty acids (44.4% of the total monomers), mostly with mid-chain hydroxyl and epoxy groups, fatty acids (20.7%), and a smaller proportion of α,ω-dicarboxylic acids (6.5%). The predominant compounds are 10,16-dihydroxy hexadecanoic acid (17.7-25.2%) and 9,10,18-trihydroxyoctadecanoic acid (15.6-18.0%). Alkanols represent 2.8% and aromatic compounds 12.8%, mainly coumarates. Isolation of cuticles from Q. suber leaves was performed using an enzymatic separation procedure and the fragments were analysed. Cuticle isolation is difficult and direct depolymerisation applied to whole leaves proved a suitable method to study cutin monomeric composition, which did not differ substantially to that of the isolated cuticles. No differences between provenances were found regarding cutin content and composition, thereby ruling out a significant genetic determination of these traits, but rather a highly adaptive phenotypic plasticity of cork oak. Although overall similar in their chemical nature, cutin and suberin in cork oak differ in the proportion of the major chemical families, i.e. ω-hydroxy acids, α,ω-diacids, and fatty acids.
本研究测定了六个具有不同种子地理起源的栓皮栎（Quercus suber）起源的叶片角质层的含量和组成，这些起源分布于该物种的自然分布区。叶片表面的角质层平均为 518μg/cm²的叶面积，占叶片干重的 6.7%，不同起源之间没有显著差异。通过对整个叶片进行酯交换反应进行角质层解聚。本文首次报道了栓皮栎叶片的角质层组成。它主要由长链脂肪族 ω-羟基脂肪酸（占总单体的 44.4%）组成，主要带有中链羟基和环氧化物基团、脂肪酸（20.7%）和较小比例的α，ω-二羧酸（6.5%）。主要化合物为 10,16-二羟基十六烷酸（17.7-25.2%）和 9,10,18-三羟基十八烷酸（15.6-18.0%）。烷醇占 2.8%，芳香族化合物占 12.8%，主要为香豆素。使用酶分离程序从栓皮栎叶片中分离角质层，并对碎片进行分析。角质层的分离很困难，直接对整个叶片进行解聚被证明是研究角质层单体组成的一种合适方法，其组成与分离的角质层没有显著差异。不同起源的栓皮栎在角质层含量和组成方面没有差异，从而排除了这些性状具有显著的遗传决定因素，而是栓皮栎具有高度适应性的表型可塑性。尽管栓皮栎的角质层和木栓层在化学性质上总体相似，但它们在主要化学家族的比例上存在差异，即 ω-羟基酸、α，ω-二羧酸和脂肪酸。
