This study aimed to determine the effect of changes in light quality on the improvement of growth and bioactive compound synthesis in red-leaf lettuce (Lactuca sativa L. ‘Sunmang’) grown in a plant factory with electrical lighting. Lettuce seedlings were subjected to 12 light treatments combining five lighting sources: red (R; 655 nm), blue (B; 456 nm), and different ratios of red and blue light combined with three light-emitting diodes [LEDs (R9B1, R8B2, and R6B4)]. Treatments were divided into control (continuous irradiation of each light source for 4 weeks), monochromatic (changing from R to B at 1, 2, or 3 weeks after the onset of the experiments), and combined (changing from R9B1 to R8B2 or R6B4 at 2 or 3 weeks after the onset of the experiments). Growth and photosynthetic rates of lettuce increased with increasing ratios of red light, whereas chlorophyll and antioxidant phenolic content decreased with increasing ratios of red light. Individual phenolic compounds, including chlorogenic, caffeic, chicoric, and ferulic acids, and kaempferol, showed a similar trend to that of total phenolics. Moreover, transcript levels of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) genes were rapidly upregulated by changing light quality from red to blue. Although the concentration of bioactive compounds in lettuce leaves enhanced with blue light, their contents per lettuce plant were more directly affected by red light, suggesting that biomass as well as bioactive compounds’ accumulation should be considered to enhance phytochemical production. In addition, results suggested that growth and antioxidant phenolic compound synthesis were more sensitive to monochromatic light than to combined light variations. In conclusion, the adjustment of light quality at a specific growth stage should be considered as a strategic tool for improving crop yield, nutritional quality, or both in a plant factory with electrical lighting.

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Rose (Rosa hybrida L.) 'Asami Red' plants were grown in a glasshouse for a year and the preharvest environmental parameters, and morphological and physiological parameters of individual cut flowers at harvest and during the postharvest period were recorded. Principal component analysis showed interrelations between the parameters: rose plants grown under "dry" conditions, i.e., high temperature, low relative humidity, and consequent high vapor pressure deficit, produced cut flowers having delayed wilting symptoms, resulting in a long vase life; cut roses with a high transpiration rate in the dark at harvest could not maintain their water relations properly, resulting in a shorter vase life; roses grown under "dry" conditions had small stomata and a low transpiration rate in the dark at harvest. These results indicate that humidity conditions are key preharvest environmental factor affecting the vase life of cut roses, and roses grown under "dry" conditions develop more functional stomata, regulate their water relations properly after harvest, and have a longer vase life. Multiple regression analysis to predict the vase life from preharvest environmental parameters and morphological and physiological parameters at harvest generated a significant equation (Y = −0.0971·X 1 + 0.0242·X 2 − 0.3275·X 3 − 2.84792·X 4 − 0.4859·X 5 + 15.397, where Y is the number of days of vase life; X 1 -X 5 are the daily minimum relative humidity, ratio of the stem diameter of the neck and cut end, stomatal width, water potential in the light, and transpiration rate in the dark, respectively; R 2 = 0.618; P < 0.001).

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Botrytis cinerea (B. cinerea) is one of the necrotrophic pathogens resulting in the heaviest commercial losses in cut rose flowers, and the severity of gray mold disease partly depends on the presence of ethylene during the storage and transport. The effectiveness of nano silver (NS) and salicylic acid (SA) was assessed as a novel control agent in protecting the cut rose flowers against B. cinerea infection and ethylene damages. The efficacy of NS and SA was compared with an inoculated control (CON). A non-treated control (NT) was also used to evaluate the natural infection process. The results indicated that pretreatment with 20 mg L−1 NS significantly reduced B. cinerea growth in rose petals during vase periods. NS effectively suppressed the mRNA levels of ethylene biosynthesis genes (RhACS2, RhACS4, and RhACO1) and the reduction in expression levels of ethylene receptor genes (RhETR1, RhETR2, and RhETR5) and the downstream regulator RhCTR2 in rose petals after B. cinerea inoculation. NS application also decreased the expression of the B. cinerea snod-prot-like 1 (Bcspl1) gene which acts as the virulence factor in cut roses. In NS flowers, the maximum quantum yield of PSII (Fv/Fm) value was higher and the leaf temperature was lower on day 1, suggesting that these factors can be used for detecting B. cinerea infection and water stress in cut rose flowers. Furthermore, NS improved water relations and extended the vase life of cut rose flowers by 3.3 d, compared with that of NT flowers. In contrast, SA had no inhibitive effects on both B. cinerea growth and ethylene response in cut roses. The findings from the present study highlight NS as a promising new candidate for preventing B. cinerea infection and ethylene damages and for improving the postharvest quality of cut roses exported overseas.