Wetting behavior on wheat leaves surface by adding different surfactants

The wettability of chemical pesticides on the surfaces of crop leaves is crucial for enhancing the efficiency of chemical solutions. This work examined the wetting behavior of 28-Epimotabrassinolide (28-HB) combined with various surfactants on the adaxial and abaxial leaves at the jointing and boot stages of wheat. The microstructure of the leaf surface was characterized by ultra-depth microscopy, and the surface free energy (SFE) of the leaf was calculated by the Owens–Wendt–Rabel–Kaelble (OWRK) method. The surface tension of the 28-HB solution with different surfactants added and the contact angle on the leaf surface at the jointing and boot stages were measured. Compared with the boot stage, the wettability of the adaxial and abaxial wheat leaves was superior to that of the jointing stage. The addition of surfactants to the 28-HB improved the spreading behavior of droplets on the surface of leaves. Specifically, when fatty lcohol polyoxyethylene ether (AEO9) was added to 28-HB, the wettability of the droplets on the jointing wheat leaf surface was greatly enhanced. Additionally, cetyltrimethylammonium bromide (CTAB) and sodium lauryl sulfate (SDS) improve the wettability of 28-HB on wheat leaves at the boot stage. When the surface tension of the solution is lower than the free energy of the solid surface, the dispersion component in the free energy of the leaf surface aligns with the dispersion component in the surface tension of the solution, facilitating maximum wettability of the solution on the leaf surface. This work offers a fresh perspective on enhancing the efficiency of surfactants in achieving superhydrophobic leaf wetting.