Table_1_Leaf Cuticular Transpiration Barrier Organization in Tea Tree Under Normal Growth Conditions.docx

The cuticle plays a major role in restricting nonstomatal water transpiration in plants. There is therefore a long-standing interest to understand the structure and function of the plant cuticle. Although many efforts have been devoted, it remains controversial to what degree the various cuticular parameters contribute to the water transpiration barrier. In this study, eight tea germplasms were grown under normal conditions; cuticle thickness, wax coverage, and compositions were analyzed from the epicuticular waxes and the intracuticular waxes of both leaf surfaces. The cuticular transpiration rates were measured from the individual leaf surface as well as the intracuticular wax layer. Epicuticular wax resistances were also calculated from both leaf surfaces. The correlation analysis between the cuticular transpiration rates (or resistances) and various cuticle parameters was conducted. We found that the abaxial cuticular transpiration rates accounted for 64–78% of total cuticular transpiration and were the dominant factor in the variations for the total cuticular transpiration. On the adaxial surface, the major cuticular transpiration barrier was located on the intracuticular waxes; however, on the abaxial surface, the major cuticular transpiration barrier was located on the epicuticular waxes. Cuticle thickness was not a factor affecting cuticular transpiration. However, the abaxial epicuticular wax coverage was found to be significantly and positively correlated with the abaxial epicuticular resistance. Correlation analysis suggested that the very-long-chain aliphatic compounds and glycol esters play major roles in the cuticular transpiration barrier in tea trees grown under normal conditions. Our results provided novel insights about the complex structure–functional relationships in the tea cuticle.

植物角质层（cuticle）在限制植物非气孔水分蒸腾过程中发挥核心作用。长期以来，学界始终致力于解析植物角质层的结构与功能。尽管已有大量研究投入该领域，但各类角质层参数对蒸腾屏障的贡献程度仍存在争议。本研究选取8份茶树种质资源于正常栽培条件下种植，分别分析了叶片正反两面表皮蜡质（epicuticular waxes）与角质层内蜡质（intracuticular waxes）的厚度、蜡质覆盖度及组成成分。我们测定了单张叶片正反两面的角质层蒸腾速率，检测了角质层内蜡质层的相关指标，并计算了叶片正反两面的表皮蜡质抗蒸腾能力。随后，针对角质层蒸腾速率（或抗蒸腾能力）与各类角质层参数开展了相关性分析。研究结果显示，叶背（abaxial）角质层蒸腾速率占总角质层蒸腾量的64%~78%，是影响总角质层蒸腾量变化的主导因素。在近轴面（adaxial，即叶面），主要的抗蒸腾屏障位于角质层内蜡质层；而在叶背（abaxial），主要抗蒸腾屏障则为表皮蜡质层。角质层厚度并非影响角质层蒸腾的关键因素，但叶背表皮蜡质覆盖度与叶背表皮蜡质抗蒸腾能力呈显著正相关。相关性分析结果表明，超长链脂肪族化合物（very-long-chain aliphatic compounds）与乙二醇酯（glycol esters）在正常栽培条件下茶树的角质层抗蒸腾屏障中发挥主要作用。本研究结果为解析茶树角质层复杂的结构-功能关联提供了全新的研究视角。