according to plant species. Appelgren (1991) observed that the exposure of Pelargonium ( Pelargonium ×hortorum cv. Penny Irene) plantlets to red light (660 nm) in vitro significantly stimulated stem elongation, whereas blue light (450 nm) strongly
A study was conducted in the greenhouse to investigate the effects of red light (600-700 nm) on the subsequent occurrence of seedling infection of bell pepper, pumpkin, and tomato caused by Phytophthora capsici. Three- or 4-week-old seedlings were inoculated with zoospores or transplanted into pots filled with artificially infested soil mix. Red light treatment of seedlings reduced Phytophthora damping-off by up to 79%. Only 21% to 36% of red light-treated seedlings became infected, whereas 78% to 100% of the control seedlings, grown either in natural daylight (NDL) or under white light (WL), became infected and died. The height, and fresh and dry weight of seedlings treated with red light were significantly higher than those grown under NDL or WL.
Effects of concurrent vs. alternating blue and red light using light-emitting diodes (LEDs) on the photomixotrophic growth of potato plantlets in vitro were investigated. All seven treatments had the same 5.53 mol·m-2 daily light integral (DLI), photoperiod (16-hour day/8-hour night) and similar proportion of red light (45%) and blue light (55%). Results showed that the fresh/dry weight accumulation of potato plantlets in vitro under the concurrent blue and red light was superior than that under the alternating blue and red light, indicating that the simultaneous coexistence of blue and red light are necessary for optimum plantlet growth. Low PPF with long duration was better than high PPF with short duration under same DLI. Within the concurrent blue and red light treatments, when the duration of blue light was shorter than that of red light, timing of the blue light affected the growth of potato plantlets in vitro. Providing blue and red light together at the beginning of the photoperiod resulted in optimal growth, however plantlets illuminated with alternately blue and red light had significantly less fresh/dry weight accumulation.
cropping cycles of ornamental plants grown in controlled environments. One approach to enhancing growth is to include far-red light (λ = 700–800 nm) in the spectrum because 1) far-red light can trigger a shade-avoidance and/or acclimation response
field on 1 Sept. These unexpected results were attributed to a high plant density (320 transplants/m 2 ) that provided a continuous and heavy leaf cover, which eliminated red light (less than 700 nm) from reaching the crowns ( Takeda, 2008 ). In contrast
unfavorable conditions without affecting seed longevity, is highly desirable. Given that germination of photoblastic lettuce seeds is under light control, this stimulus may be managed to promote or retard germination. Red light promotes germination in positive
) of 100 μmol·m −2 ·s −1 or 50 μmol·m −2 ·s −1 , monochromatic blue vs. red light promoted elongation growth in all the tested bedding plant species, including petunia, calibrachoa, geranium, and marigold ( Kong et al., 2018 ), and some microgreen
before sunset and opened 0 to 60 min after sunrise (BO), a 1-h end-of-day red light treatment providing 20 µmol·m −2 ·s −1 at pot level using red LEDs (EOD R), and a control treatment with natural twilight (CTRL). Each bench was equipped with automatic
and fluorescent lamps. The spectral irradiance was recorded with a spectroradiometer and software system (FieldSpec HandHeld, ASD Inc. CO). B = blue light (450 ± 2 nm); G = green light (525 ± 3 nm); R = red light (660 ± 5 nm); IR = infrared (730 ± 5 nm
Effects of light generated by red and blue light-emitting diodes on the photomixotrophic growth of Zantedeschia jucunda `Black Magic' plantlets in vitro and tuber formation after transplant under the same PPF and photoperiod were investigated. All five treatments had the same photosynthetic photon flux (PPF, 80 ± 5 μmol·m-2·s-1) and photoperiod (16 hours daytime/8 hours nighttime), leading to the same daily light integral. Results showed that the tubular fluorescent lamp (TFL) treatment had the highest value on chlorophyll content and dry weight accumulation than other treatments using light-emitting diodes (LEDs). In LED treatments, there were no significant differences on dry weight and growth rate but with significant differences on chlorophyll content and plant height when blue light LEDs were added. It revealed that blue light was involved in plant height and chlorophyll development control mechanism. Results also showed that minor difference in 28 days of transplant production (in vitro) among treatments does not extends after 6 months of tuber formation stage grown in greenhouse. At present, blue LEDs cost much more than that of red LEDs, results of this study suggested that using red LEDs alone and powered with AC is feasible for the commercial production of Zantedeschia plantlets in vitro.