The benefits of ecosystem services provided by urban green systems have been highlighted in research on spatial and landscape planning, and the need has emerged for an integrated approach to urban green planning aiming at increasing climate mitigation and urban resilience. Research indicates that plant selection and substrate management are vital for optimizing the most important performance of green roofs, like building thermal insulation, urban heat reduction, air quality improvement, and stormwater management. In Mediterranean climates, it is essential to investigate sustainable management solutions for green roofs like the growth potential of native, low-maintenance forbs adapted to thermal and water stress on specific substrates. Medicinal species may be suitable, provided that interactions with pollutants are controlled. This study evaluates the performance of Melissa officinalis and Hypericum perforatum on experimental green roof modules under controlled conditions, comparing chemical fertilization and three different treatments with biomass from Trifolium repens used as green manure. The key metrics of fresh and dry biomass, plant cover ratio, and chlorophyll content are measured. Results show significantly higher values of cover and biomass for these two species treated with green manure in comparison to chemical fertilization, with no significant differences in chlorophyll content, indicating that T. repens is a useful source of green manure in green roof management. Overall, the results are consistent with the research goals of suggesting sustainable solutions for green roof management, since low-maintenance vegetation and green manure contribute to the elimination of chemicals in urban green.

Light quality and biostimulants regulate alkaloid biosynthesis and promote plant growth, but their combined effects on vindoline (VDL) and catharanthine (CAT) production in Catharanthus roseus remain underexplored. This study investigated the impact of different LED spectra and an arbuscular mycorrhizal fungi-based biostimulant (BS) on VDL and CAT production in indoor-grown C. roseus. After a 60-day pretreatment under white LEDs, plants were exposed to eight treatments: white (W, control), red (R), blue (B), and red-blue (RB) light, and their combinations with BS. Samples were collected before treatments (T0) and 92 days after pretreatment (T1). No mycorrhizal development was observed. VDL was detected in both roots and leaves, with higher levels in roots. R produced significantly higher mean concentrations of both VDL and CAT than W. BS significantly increased mean concentrations and total yields of both alkaloids than the untreated condition. The combination of R and BS produced the highest mean concentrations and total yields of VDL and CAT. In particular, it resulted in a significantly higher mean concentration and total yield of VDL compared to sole W. Total yields increased from T0 to T1, primarily due to a substantial rise in root yield. In conclusion, combining R and BS proved to be the most effective strategy to enhance VDL and CAT production by maximizing their total yields, which also increased over time due to greater root contribution. This underscores the importance of combining targeted treatments with harvesting at specific stages to optimize alkaloid production under controlled conditions.

Light quality is a recognized driver of plant growth and secondary metabolism in Coleus blumei, a valuable source of rosmarinic acid (RA) and quercetin (QU), whereas its combination with salinity stress represents a potential strategy that still requires further investigation. We evaluated four LED spectra, red–blue (RB) (6:1, control), blue (B), red (R), and RB + Far-Red, under both control (0 mM NaCl) and moderate salt stress (120 mM NaCl), measuring biomass (dry weight) and RA/QU in leaves and roots after three (T1) and five weeks (T2). Blue light produced the greatest root biomass, while the leaf dry weight under B did not differ significantly from RB or RBfr. RA peaked at T2 under B in leaves and under R in roots; QU was maximal under B in leaves and under RB in roots. Extending exposure from T1 to T2 markedly increased both metabolites’ yield. Salinity had little effect on biomass, increased the total QU yield, and did not enhance the total RA yield. These results indicate that targeted LED regimes and longer exposure can raise the yields of bioactive compounds, and that combining specific spectra with moderate salinity is an effective strategy for selectively increasing quercetin accumulation in indoor-grown C. blumei.

Madagascar periwinkle [Catharanthus roseus (L.) G. Don] produces vindoline and catharanthine, key precursors used in the semi-synthesis of the high-value anticancer alkaloids vinblastine and vincristine. Closed plant production systems (CPPS) allow precise application of environmental stimuli, including light spectrum and plasma-activated water (PAW). In a previous study, we demonstrated the potential of combining artificial light (white and red) and PAW to enhance the production of these alkaloids in periwinkle grown under controlled CPPS conditions. The present study expands this approach by adopting a more scalable PAW application method and a broader range of LED light spectra to evaluate their effects on vindoline and catharanthine accumulation. After a 37-day pre-treatment under white LEDs in environmentally controlled rooms, plants were subjected to fourteen treatments: phosphor-converted warm white (WW-P, control), red (R), blue (B), red–blue (RB), red–blue–far red (RBFR), phosphor-converted cool white (CW-P), and color-mixed white (W-CM) LED light, each with or without PAW. Plant growth and alkaloid-related responses were assessed at three sampling times: before treatment application (T0), 47 (T1), and 55 (T2) days after pre-treatment. RB produced the highest total vindoline and catharanthine yields [sum of leaf and root yields, with each organ yield calculated as organ dry mass (DM, g plant⁻¹) × organ alkaloid concentration (µg g⁻¹ DM)], reaching 228.0 ± 16.9 and 338.0 ± 27.0 µg plant⁻¹, respectively, which were significantly higher than those obtained under all other light spectra (1.4-fold for vindoline and 1.3-fold for catharanthine relative to WW-P), except for W-CM, for which no significant differences were observed. PAW significantly increased total vindoline and catharanthine yields, reaching 211.0 ± 8.0 and 278.0 ± 11.0 µg plant⁻¹, respectively, corresponding to 1.9- and 1.3-fold increases compared with the untreated condition. Sampling time had a strong effect on total vindoline and catharanthine yields, increasing from 6.0 ± 0.7 and 13.9 ± 1.7 µg plant⁻¹, respectively, at T0, to 258.7 ± 9.8 and 414.0 ± 17.0 µg plant⁻¹, respectively, at T2, corresponding to 43.1- and 29.8-fold increases. In conclusion, the combined use of RB light and PAW, together with harvesting at T2, represented the most effective strategy to achieve high vindoline and catharanthine production, as it enhanced the total yields of both alkaloids.