Influence of additional far-red light on the photosynthetic and growth parameters of lettuce plants and the resistance of the photosynthetic apparatus to high irradiance (original) (raw)
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Evidence for Yellow Light Suppression of Lettuce Growth¶
Photochemistry and Photobiology, 2007
Researchers studying plant growth under different lamp types often attribute differences in growth to a blue light response. Lettuce plants were grown in six blue light treatments comprising five blue light fractions (0, 2, 6% from high-pressure sodium [HPS] lamps and 6, 12, 26% from metal halide [MH] lamps). Lettuce chlorophyll concentration, dry mass, leaf area and specific leaf area under the HPS and MH 6% blue were significantly different, suggesting wavelengths other than blue and red affected plant growth. Results were reproducible in two replicate studies at each of two photosynthetic photon fluxes, 200 and 500 mol m Ϫ2 s Ϫ1 . We graphed the data against absolute blue light, phytochrome photoequilibrium, phototropic blue, UV, red:far red, blue:red, blue: far red and 'yellow' light fraction. Only the 'yellow' wavelength range (580-600 nm) explained the differences between the two lamp types.
V International Symposium on Artificial Lighting in Horticulture, 2006
Impact of controlled illumination spectrum on photosynthetic system and productivity of lettuce (Lactuca sativa L. cv. Grand Rapids) grown in phytotron was investigated. The variable-spectrum lighting modules were designed using four types of high-power light-emitting diodes (LEDs) with emission peaked in red at the wavelengths of 660 nm and 640 nm, in blue at 455 nm, and in far-red at 735 nm. Biometric characteristics, pigments content and photosynthesis intensity in lettuce grown under eight different light irradiance were measured and compared. A corresponding experiment under a conventional high-pressure sodium lamp was also performed for reference. The treatments were carried out under photoperiod of 14 hand 21115·C (day/night) temperature. Lettuce was grown for 29 days after sowing in a phytotron chamber. Stomata size of lettuce grown under LED was larger than that of the plants growing under high-pressure sodium lamp. The lowest number and largest size of stomata were observed under light without the red component, peaked at 660 nm. Elimination of the blue component (455 nm) resulted in an enhancement of fresh mass production and increased leaf area, but the photosynthetic productivity did not sbow similar effect. Tbe cblorophylls content in lettuce leaves was high during tbe entire growtb period, but strongly decreased at the end of tbe treatment without blue ligbt. Tbe photosynthesis in lettuce leaves was most intensive under irradiance without the far-red component (735 nm). We conclude that productivity of lettuce can be optimized by adjusting the light spectrum and flux density.
Plants
This study focused on the physiology, growth and antioxidant activity response of hydroponically grown lettuce (Lactuca sativa L.) under sole-source LED lighting of differing spectra. Lighting spectra were provided by differing combinations of LEDs of three different peak wavelengths, (Blue 435, Blue 450, and Red 663 nm) with ratios of B450/R663: 1.25 ± 0.1, B450/R663: 1.25 ± 0.1, and B450/R663 1:1 at two light intensities of photosynthetically active radiation (PAR) (270 μmol m−2 s−1 and 60 μmol m−2 s−1). A further experiment was conducted, in which Blue and Red LEDs were supplemented with Green (Blue 450, Red 663, and Green 520 nm) with ratios of B435/R663: 1.25 ± 0.1, B450/R663/G520: 1/0.73/0.26, and B450/R663: 1.25 ± 0.1. LED light intensities under the different spectra were adjusted to deliver the same level of PAR (270 ± 20 μmol m−2 s−1). Results from the first experiment showed that increased fraction of blue 435 nm in combination with red light at 663 nm at high irradiance ...
Agriculture, 2020
Plant production in urban areas is receiving much attention due to its potential role in feeding the rapidly growing population of city dwellers. However, higher energy demands in urban plant factories are among the key challenges that need to be addressed. Artificial lighting is responsible for the most significant levels of energy consumption in plant factories; therefore, lighting systems must be modulated in consideration of the sustainable food-energy nexus. In this context, low light irradiation using blue (B) and red (R) LED was applied in a plant factory for the growth of red leaf lettuce (Lactuca sativa L. var Lollo rosso) to evaluate the growth performance and functional quality. The tested B (450 nm) and R (660 nm) light ratios were B/R = 5:1; 3:1; 1:1; 1:3, and 1:5, with a photosynthetic photon flux density (PPFD) of 90 ± 3 µmol m −2 s −1. In the plant factory, the photoperiod, temperature, RH, and CO 2 conditions were 16 h d −1 , 20 ± 0.5 • C, 65% ± 5%, and 360 ± 10 µL L −1 , respectively. The lettuce was harvested 10 and 20 days after the commencement of LED light treatment (DAT). In this study, normal photosynthetic activity and good visual quality of the lettuce were observed. The results show that a higher fraction of R (B/R = 1:5) significantly increased plant growth parameters such as plant height, leaf area, specific leaf area, plant fresh and dry weight, and carbohydrate content. By contrast, a higher fraction of B (B/R = 5:1) significantly increased the photosynthetic parameters and contents of pigment and phenolic compounds. The rate of photosynthetic performance, carbohydrates (except starch), and content of phenolic compounds were highest after 10 DAT, whereas the pigment contents did not significantly differ at the different growth stages. It is concluded that high R fractions favor plant growth and carbohydrate content, while high B fractions favor photosynthetic performance and the accumulation of pigments and phenolic compounds in red leaf lettuce under limited lighting conditions. This study will help in designing artificial lighting conditions for plant factory production to reduce energy demands.
Journal of Plant Growth Regulation, 2020
Photosynthesis and stomata dynamically respond to transient changes in light intensity; however, information regarding their long-term responses to the light intensity is limited. In the current study, biophysical properties of photosynthetic apparatus and stomatal characteristics of lettuce plants were investigated in response to long-term exposure to different photosynthetic photon flux densities (PPFDs) [75, 150, 300, and 600 µmol m −2 s −1 ]. Contrary to leaf growth, SLA decreased with increasing light intensity (i.e., thicker leaves under higher light intensity). Improving effect of higher light intensity on leaf fresh and dry weights was time dependent, in a way that the largest difference in biomass gain was observed following 40 days of exposure to the light treatments. Depending on the leaf developmental stages, exposure to higher light intensities caused faster development of photosynthesis system [in terms of improvement in the maximum quantum efficiency of photosystem II (PSII) and non-photochemical quenching (NPQ)] compared to lower light intensities. PSII performance index on an absorption basis was the highest under 600 PPFD. Small-sized stomata with narrow pore apertures were observed in plants grown under 75 PPFD; however, due to improvement in photosynthetic capacity and also the growth of the plants, water use efficiency (WUE) increased in a light intensity-dependent manner and the highest WUE was detected in 600 PPFD-exposed plants. In conclusion, exposing lettuce plants to higher light intensities (non-stress threshold levels) results in higher accumulation of biomass, faster development of photosynthetic system, and improved WUE.
The objective of this study was to evaluate growth and physiological responses of 'Cherokee' and 'Waldmann's Green' lettuce (Lactuca sativa) exposed to small changes in light quality and intensity within a 24-h period. Three pre-dawn (PD; 0600 to 0700) and three end-of-day (EOD; 2100 to 2200) treatments were evaluated in the study, each providing 50 ± 2 µmol·m −2 ·s −1 of either blue, red, or broadband white light from light-emitting diodes (LEDs). To account for the main daily light integral (DLI), broadband white LEDs provided 210 ± 2 µmol·m −2 ·s −1 from 0700 to 2200 or from 0600 to 2100 for the PD or EOD treatments, respectively. A control treatment was included which provided 200 ± 2 µmol· m −2 ·s −1 of white light from 0600 to 2200. All treatments provided a DLI of 11.5 mol·m −2 ·day −1 over a 16-h photoperiod. Regardless of cultivar, no treatment difference was measured for hypocotyl length or leaf number. However, plants grown under EOD-blue or PD-white had up to 26% larger leaves than those grown under PD-red and 20% larger leaves than control. In addition, plants grown under EOD-blue produced up to 18% more shoot fresh mass compared to those grown under control, EOD-red, or PD-red. Contrasts for gas-exchange data collected during the main photoperiod showed that light quality was not significant within PD or EOD for any of the parameters evaluated. However, regardless of light quality, stomatal conductance (g s) and transpiration (E) were up to 34% and 42% higher, respectively, for EOD-grown plants compared to control. Our results suggest that 1 h of low intensity EOD-blue light has the potential to promote lettuce growth by increasing leaf area and shoot fresh mass when the main DLI from sole-source lighting is provided by broadband white LEDs.
Journal of the Faculty of Agriculture, Kyushu University
This study discussed the influence of light-emitting diodes (LEDs) with red, blue, green, and yellow light on the growth and photosynthetic efficiency of Boston lettuce and Ziyan lettuce as a reference for lettuce production in plant factories. The experiments were conducted in a plant factory under a 120 µmole・m-2 ・s-1 photosynthetic photon flux density, CO 2 concentration of 1000 ppm, and daytime and nighttime temperature of 25°C/18 h and 17°C/6 h, respectively. The experiment results revealed that after 15 days of treatment under different spectral qualities, the appearances of the two lettuce leaves differed slightly. The fresh and dry weights of the Boston lettuce were highest under green light treatment. The fresh and dry weights of the Ziyan lettuce were higher under red and green light, and blue light helped the leaves to change color. In addition, photosynthesis analyzers were used to investigate the photosynthetic efficiency of the two types of lettuce under the four spectral qualities under the six luminous intensity levels of 20, 40, 60, 80, 100, and 120 µmole・m-2 ・s-1 and six CO 2 concentrations of 400, 600, 800, 1000, 1200, and 1400 ppm. The photosynthetic efficiency of the two types of lettuce generally increased with increasing luminous intensity and CO 2 concentration. When the luminous intensity was 100 and 120 µmole・m-2 ・s-1 and the CO 2 concentration was 1200 ppm and 1400 ppm, the Boston lettuce had the highest photosynthetic efficiency under green light. When luminous intensity was 120 µmole・m-2 ・s-1 and the CO 2 concentration was over 1000 ppm, the Ziyan lettuce had the highest photosynthetic efficiency under red light. These results revealed that the monochromatic LED light most suitable for growth differed across types of lettuce. In this experiment, the yield and photosynthetic efficiency of Boston lettuce were highest under green light. Those of Ziyan lettuce were highest under red light.
Scientia Horticulturae, 2020
Light drives photosynthesis and regulates plant morphology, physiology, and phytochemical content. Using light emitting diodes (LEDs), customized spectra can be created, including spectrum that simulates solar light. The aim of this study was to assess the growth, development, and phytochemical content at three marketable stages of lettuce (transplant, baby-leaf, and head-lettuce) under a sun-simulated spectrum and common light spectra used in indoor growing systems. Oakleaf red (Salanova® 'Red Oakleaf') and green (Salanova® 'Green Oakleaf') lettuce were grown under seven spectra. A sun-simulated light treatment (SUN) was created with 5 % ultraviolet-A (UV-A), 20 % blue (B), 26 % green (G), 26 % red (R), and 23 % far-red (FR) light as percent photon flux density (PFD). In addition, five treatments of differing blue:red (B:R) ratios were evaluated: 0B:100R (100R), 20B:80R, 50B:50R, 80B:20R, and 100B:0R (100B) and fluorescent white light was used as a control (6500 K). Plants were provided with 200 ± 0.7 μmol•m −2 •s −1 biologically active radiation (300-800 nm) for 18 h and grown at 20.0 ± 0.2°C temperature. Fresh mass of lettuce in the SUN treatment was not significantly different when compared to B:R light treatments in all harvest dates despite the 36 % greater photosynthetic photon flux density (PPFD) in B:R treatments. Plant dry mass on day 17 of' Green Oakleaf' and 'Red Oakleaf' grown under 20B:80R was 15-39 % greater than those grown in 100B and SUN. When calculating total dry mass accumulation to cumulative yield photon flux density (YPFD), plants in SUN treatment accumulated the same dry mass per YPFD input (mg mol −1). Leaf area at day 42 of plants in 100B, SUN, and FL was 39-78 % greater than plants in B:R treatments. At final harvest (day 42), plant stem length in SUN was 2.1-4.4 times longer than in all other treatments, indicating bolting and flowering initiation. Both total phenolic and anthocyanin concentrations were greater in the B:R treatments than in SUN, 100R, and 100B treatments. This study presents baseline information for lettuce responses under LED-simulated SUN spectrum when compared to common B:R treatments and offers insights on lettuce growth and morphology under different spectra at multiple growth stages.