目的 研究香蕉树冠层不同时期蕉叶的正、反面润湿行为，以期为农药雾滴在蕉叶表面滞留调控机制提供依据。方法 采用接触角测量仪表征蕉叶表面的静态润湿性能；利用高速摄像机记录液滴在蕉叶表面的动态润湿行为；使用场发射扫描电镜对蕉叶表面进行微观形貌观察获取表面结构信息，并借助傅立叶红外光谱仪分析其表面化学成分；基于Wenzel和Cassie润湿理论构建蕉叶表面微观结构模型，建立润湿方程阐述其润湿机理。结果 扫描电镜发现蕉叶正面呈现微米?纳米级双层复合结构，在微米级突起结构上布满了纳米级乳突结构，分布为4.6个/μm2，条状突起宽度为(16.03±3.48) μm，乳突平均直径为(0.116±0.068) μm，蕉叶背面微米级条状突起结构尺寸大于正面，宽度为(74.25±9.80) μm，纳米级结构上呈现出网状突起，宽度为(2.35±0.49) μm，蕉叶背面的润湿性普遍大于正面的；在不同生长时期的蕉叶中，剑叶正面表现出亲水性，静态接触角(Contact angle，CA)为71.46°±6.02°，而其他时期的蕉叶正、反面均表现出弱疏水性，表明嫩叶正面具有更强的润湿和铺展能力；通过对成熟蕉叶正表面构建Wenzel和Cassie润湿模型，分析计算得出成熟蕉叶正表面本征CA为20.76°，具有超亲水性，表明其纳米级乳突结构为多糖。结论 蕉叶表面疏水的微米?纳米级双层复合结构以及亲水的化学成分共同作用导致了其表面表现出弱疏水性的润湿状态，而纳米级乳突结构的多糖是导致其表面具有亲水效应及高黏附效应的原因。
Objective The wetting behavior of the front and back surfaces of banana leaves at different growth stages of the banana tree canopy was studied, in order to provide a basis for the regulation mechanism of pesticide droplets retention on the surface of banana leaves. Method The static wetting properties of the banana leaf surface were characterized by a contact angle measuring instrument, the dynamic wetting behavior of droplets on the surface of the banana leaf was recorded by a high-speed camera, and the structural information of the banana leaf surface was observed by a field emission scanning electron microscope. The surface chemical composition was analyzed using the Fourier transform infrared spectrometer. The surface microstructure model of banana leaf was constructed based on the Wenzel and Cassie wetting theory, and the wetting equation was established to describe its wetting mechanism. Result Scanning electron microscopic observation showed that the front surface of banana leaves presented a micro-nano-scale double-layer composite structure, the micro-scale protrusion structure was covered with nano-scale papillary structures with a density of about 4.6 pieces/μm2, the strip-like protrusion width was (16.03±3.48) μm, the average diameter of papillae was (0.116±0.068) μm, the size of micron-scale strip-like protrusions on the back of banana leaves was larger than that of the front, and the width was (74.25±9.80) μm, the nano-scale structure had mesh-like protrusions with a width of (2.35±0.49) μm, and the wettability of the back of banana leaves was generally higher than that of the front. For banana leaves at different growth stages, the front of flag leaves showed hydrophilicity with contact angle of 71.46°±6.02°, while the front and back of banana leaves at other stages showed weak hydrophobicity, indicating that the front surface of young leaves had stronger wetting and spreading ability. By constructing the Wenzel and Cassie wetting models for the front surface of mature banana leaves, the intrinsic contact angle of the front surface of mature banana leaves was 20.76° showed super-hydrophilic based on analysis and calculation, indicating that its nano-scale papillary structure was polysaccharide. Conclusion The combination of the hydrophobic micro-nano bilayer composite structure and the hydrophilic chemical components on the surface of banana leaves leads to the wet state of weak hydrophobicity on the surface, and the polysaccharide of the nano-papillary structure is responsible for hydrophilic effect and high adhesion effect of the banana leaf surface.