Can plants grow on the Moon and Mars: seed germination enhancement using magnesium oxide coated halloysite nanotubes (MgO HNTs)
This study examines the application of metal coated nanotubes, specifically magnesium oxide coated halloysite nanotubes (MgO HNTs), to enhance seed germination and early plant development under Earth, lunar, and Martian soil conditions. MgO HNTs were synthesized through an electrodeposition process and characterized by scanning electron microscopy to confirm successful surface modification. Growth experiments using Heirloom Cherry Tomato and Golden Tomato seeds were conducted under hydroponic and soil based conditions and subsequently extended to lunar and Martian regolith simulants. A response surface methodology approach based on a Box Behnken design was used to evaluate the effects of temperature, MgO HNT concentration, and light duration on multiple growth responses. Seedling length and the root length stress tolerance index were identified as the most responsive indicators of MgO HNT treatment. Optimal conditions consisting of 25 C, 12 h light exposure, and 100 mg per L MgO HNTs produced the greatest increases in root and shoot length in Earth soil simulants. Validation experiments in extraterrestrial regolith analogs showed that MgO HNTs supported germination, root penetration, and overall seedling vigor under nutrient limited and high stress conditions. Lunar regolith exhibited maximal root development at 100 mg per L, whereas Martian regolith showed optimal growth at 10 mg per L, reflecting differences in mineral composition and oxidative characteristics. These findings demonstrate that MgO HNTs can enhance early plant development across both terrestrial and extraterrestrial substrates and support their potential use as nanomaterial based amendments for sustainable plant cultivation in Earth and space environments.