From Antarctic Regolith to Lunar Greenhouses: Mechanistic Insights into Brassica rapa Photosystem II Dynamics for Sustainable Space Agriculture

Sustainable agriculture systems utilizing in-situ resources are crucial for future human missions to the Moon and Mars. Antarctic regolith, a terrestrial analog of lunar soil, offers an opportunity to understand how plants respond physiologically to nutrient-poor extraterrestrial substrates. This study assessed biomass production and photosystem II (PSII) photochemistry in Brassica rapa grown in Antarctic regolith under nutrient-enriched (Hoagland solution) and nutrient-deficient (double-distilled water) conditions, using vermiculated soil as a control and soil amendment. Biomass accumulation significantly improved with nutrient supplementation. Chlorophyll fluorescence parameters, including Fv/Fm, ΦPSII, qP, NPQ, and RFD, indicated severe inhibition of PSII processes and activation of photoprotective responses in the plants grown in untreated regolith. Normalized fast chlorophyll fluorescence transients (OJIPs) revealed slowed electron transport kinetics and reduced PSII efficiency in nutrient-deficient regolith-grown plants, while differential l- and K-band analyses indicated weakened PSII connectivity and partial inactivation of the oxygen-evolving complex specifically under nutrient deprivation conditions. OJIP-derived parameters (PIABS, ABS/RC, TRo/RC, ETo/RC, DIo/RC) quantitatively confirmed these functional disruptions in PSII, with nutrient supplementation reversing impairments and optimizing energy fluxes. Our results suggest Antarctic regolith can serve as a functional lunar simulant in the preflight, on-Earth experiments. Nutrient and substrate optimization can effectively maintain PSII performance high, offering a foundation for future extraterrestrial plant-based life support systems with optimized photosynthesis and biomass production.