Seed Priming with Ulva lactuca L. in Cultivars Grown in Martian and Lunar Regolith Analogues

As human settlements expand to lunar and Martian bases, optimizing food production in these environments becomes crucial. This study investigates the use of macroalgae, specifically Ulva lactuca L., as an affordable, sustainable approach for seed priming to enhance germination in extraterrestrial soils. The focus was on the germination and growth of Capsicum annuum L. (pepper), Lactuca sativa L. (lettuce), Cicer arietinum L. (chickpea), and Pisum sativum L. (pea) in simulated Martian and lunar regolith. Two concentrations of U. lactuca powder (0.2 and 0.4 g · L⁻¹) were tested under controlled conditions. The study also conducted a qualitative chemical analysis of U. lactuca to identify bioactive components essential for phytohormone formation. The germination and emergence rates of the seeds in the lunar regolith were higher than those in the Martian regolith. Martian regolith's optimal treatment for pea and chickpea seed germination was 0.2 g · L⁻¹, which also favored seedling emergence. In the lunar regolith, optimal germination rates for pea seeds were observed with both treatments and chickpea seeds. The germination percentage of lettuce seeds in the lunar regolith was higher than the control, with 0.2 g · L⁻¹, while there was no significant difference for the other seeds. The study recommends the application of U. lactuca powder as an effective biostimulant for the examined cultivars due to the presence of plant growth regulators (PGRs) that enhance germination and seedling emergence under challenging conditions.