Reaching Natural Growth: Light Quality Effects on Plant Performance in Indoor Growth Facilities

High production of flavonols and anthocyanins in Eruca sativa (Mill) Thell plants at high artificial LED light intensities

Eruca sativa (arugula) is a food crop containing valuable bioactive flavonoids. Plants growing with monochrome light-emitting diodes (LED) and "binary" light sources, including red/blue (RB), were tested using HPLC-DAD-ESI-MS/MS. Most artificial lighting options with a high intensity of 1000 μmol m^-2s^-1 (except for warm white light) resulted in an almost 20-fold increase in flavonol productivity. Monochromatic sources had no advantage over white light in terms of increasing anthocyanin productivity. However, RB light increased the anthocyanin content and productivity of E. sativa plants by more than ten times compared to white light. Plant growth on monochromatic and binary sources at high intensities was comparable to that on white light. Measurement of the content of chlorophyll and its degradation product, phyllobilins, showed that plants are not under stressful conditions. Overall, our data show that a significant increase in flavonoid content can be achieved without a loss of arugula plant biomass.

Growth of alpine grassland will start and stop earlier under climate warming

Alpine plants have evolved a tight seasonal cycle of growth and senescence to cope with a short growing season. The potential growing season length (GSL) is increasing because of climate warming, possibly prolonging plant growth above- and belowground. We tested whether growth dynamics in typical alpine grassland are altered when the natural GSL (2-3 months) is experimentally advanced and thus, prolonged by 2-4 months. Additional summer months did not extend the growing period, as canopy browning started 34-41 days after the start of the season, even when GSL was more than doubled. Less than 10% of roots were produced during the added months, suggesting that root growth was as conservative as leaf growth. Few species showed a weak second greening under prolonged GSL, but not the dominant sedge. A longer growing season under future climate may therefore not extend growth in this widespread alpine community, but will foster species that follow a less strict phenology.