Selective Wax Cuticle Removal Using Green Wavelength Lasers: A Non-Invasive Method for Enhancing Foliar Uptake

Foliar application of agrochemicals can be extremely inefficient due to the low permeability of leaf cuticular surfaces to compounds, which cannot be compensated for by the stomata whose area is limited. To address this issue, we propose a laser-based selective wax ablation method that improves the penetration of substances into the leaf and enhances their uptake into the phloem for transport across tissue. Our investigation studies the effectiveness and non-invasive properties of using a 532 nm wavelength Nd: YAG laser to improve the penetration of foliar-applied substances into citrus leaves. The penetration enhancement achieved through laser treatment was demonstrated using two complementary methods. First, fluorescent glucose was applied to the treated area, allowing for real-time visualization and quantification of its absorption and distribution over time. The fluorescence imaging results confirmed that the removal of the wax cuticle significantly facilitated substance uptake. Second, Laser-Induced Breakdown Spectroscopy (LIBS) was used to quantify the uptake of zinc (Zn), a key component of the applied fertilizer, in laser-treated areas compared to control leaves. The LIBS analysis provided direct evidence of increased Zn absorption, further validating the effectiveness of the laser treatment in enhancing agrochemical penetration.