Comparison of Biochemical and Physiological Properties of Two Brassica Microgreens Cultivated in Two Growth Systems

Microgreens are promising crops for low-input systems, but the roles of species traits and root environments under uncontrolled greenhouse conditions are not yet fully addressed. In this study, mibuna and pak choi were evaluated in the presence or absence of substrate to clarify how genetic and physical factors shape growth and biochemical composition. Clear species-dependent differences emerged. Pak choi showed higher constitutive levels of chlorophyll a, anthocyanins, and key osmotic ions, and these features contributed to a more hydrated tissue profile. Mibuna instead exhibited a higher dry matter content, approximately 7% compared with 5.86% in pak choi, and a lighter canopy. The use of peat markedly improved overall growth. Fresh yield increased by more than 50%, and dry yield increased by almost 48% compared with the substrate-free system. Peat also enhanced organic acid metabolism, with malate and citrate increasing by 277 and 102%, respectively. Despite such differences, nitrate concentrations remained low and within safe limits for leafy vegetables in all treatments. The results indicate that species identity and the cultivation system significantly shaped overall microgreen performance under low-input conditions. Understanding these drivers provides a foundation for optimizing production while maintaining desirable nutritional traits.