Taylor, G., & Davies, W. J. (1985). The Control Of Leaf Growth Of Betula And Acer By Photoenvironment. New Phytol, 101(2), 259–268.
Abstract: Leaf extension of one‐year‐old seedlings of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.), was measured using linear variable transducers (LVDTs) interfaced to a microcomputer. Birch and sycamore seedlings exhibited contrasting patterns of leaf extension during a diurnal cycle with a 16 h photoperiod. Birch leaves grew more rapidly when illuminated; growth during the photoperiod was approximately doubled when compared with growth in the dark. Mean relative growth rates ±SE at ‘lights‐on + 3 h’ and ‘lights‐off + 5 h’ were 0.0136 ± 0.0016 and 0.0066 ± 0.0005 h−1 respectively. In direct contrast, growth of sycamore leaves was increased when leaves were darkened; mean relative growth rates + SE at ‘lights‐on+3 h’ and ‘lights‐off + 5 h’ were 0.0056 ± 0.0005 and 0.0094 ± 0.0008 h‐1 respectively.
When leaves of birch and sycamore were darkened, increased leaf turgor was measured in both species, but only in sycamore was this higher night‐time turgor associated with a higher rate of leaf growth.
Cell wall extensibility (WEX), an indication of the ability of cell walls to loosen and extend irreversibly, and cell surface pH were assessed in darkened and illuminated leaves of both species. An increase in WEX was measured when birch leaves were illuminated (P≤ 0.001) and this was accompanied by a decline in cell surface pH (P≤ 0.001). However, when leaves of sycamore were illuminated, WEX declined (P≤ 005) and cell surface pH increased (P≤ 0.001).
The ability of these species to survive beneath a woodland canopy is discussed in relation to the cellular factors controlling their leaf growth.
Kim, Y. J., Kim, H. M., Kim, H. M., Jeong, B. R., Lee, H. - J., Kim, H. - J., et al. (2018). Ice plant growth and phytochemical concentrations are affected by light quality and intensity of monochromatic light-emitting diodes. Hortic. Environ. Biotechnol., 59(4), 529–536.
Abstract: The ice plant (Mesembryanthemum crystallinum L.), widely known to be an effective cure for diabetes mellitus, is also a functional crop. This study was conducted to examine the effects of light quality and intensity of monochromatic light-emitting diodes (LEDs) on ice plant growth and phytochemical concentrations in a closed-type plant production system. Ice plant seedlings were transplanted into a deep floating technique system with a recycling nutrient solution (EC 4.0 dS m−1, pH 6.5). Fluorescent lamps, as well as monochromatic red (660 nm) and blue (450 nm) LEDs, were used at 120 ± 5 or 150 ± 5 µmol m−2 s−1 PPFD with a photoperiod of 14 h/10 h (light/dark) for 4 weeks. Ice plants showed higher growth under the high light intensity treatment, especially under the red LEDs. Furthermore, the SPAD value and photosynthetic rate were higher under the red LEDs with 150 µmol m−2 s−1 PPFD. The ice plant phytochemical composition, such as antioxidant activity and myo-inositol and pinitol concentrations, were highest under the blue LEDs with 150 µmol m−2 s−1 PPFD. Total phenolic concentration was highest under the blue LEDs with 120 µmol m−2 s−1 PPFD. Despite a slightly different dependence on light intensity, phytochemical concentrations responded positively to the blue LED treatments, as compared to other treatments. In conclusion, this study suggests that red LEDs enhance ice plant biomass, while blue LEDs induce phytochemical
Kong, Y., Stasiak, M., Dixon, M. A., & Zheng, Y. (2018). Blue light associated with low phytochrome activity can promote elongation growth as shade-avoidance response: A comparison with red light in four bedding plant species. Environmental and Experimental Botany, 155, 345–359.
Abstract: o explore the action mode of blue light on elongation growth of bedding plants, the plant growth and morphology traits of petunia (Petunia × hybrida, ‘Duvet Red’), calibrachoa (Calibrachoa × hybrida, ‘Kabloom Deep Blue’), geranium (Pelargonium × hortorum, ‘Pinto Premium Salmon’), and marigold (Tagetes erecta, ‘Antigua Orange’) were compared under four light quality treatments: (1) R, “pure” red light (660 nm); (2) B, “pure” blue light (450 nm); (3) BR, “unpure” blue light created by mixing B with a low level of R to provide B/R ≈ 9; (4) BRF, “unpure” blue light created by adding a low level of far red light to BR with red/far red ≈ 1. Continuous (24-h) light-emitting diode lighting with either 100 or 50 μmol m−2 s−1 photosynthetic photon flux density at ≈ 23℃ was used with the above treatments. After 14–20 day of lighting treatment, B promoted elongation growth compared to R, as demonstrated by a greater canopy height, main stem length, internode length, and daily main stem extension rate. However, BR showed similar or inhibitory effects on these traits relative to R, while BRF exhibited similar promotion effects as B. The calculated phytochrome photoequilibrium, an indication of phytochrome activity, was higher for R (0.89) and BR (0.74) than for B (0.49) and BRF (0.63). Adding red (or far red) light reversed the effects of B (or BR) on elongation growth and the phytochrome photoequilibrium, suggesting that blue light promotion of elongation growth is related to the lower phytochrome activity. Also, B and BRF, when compared to R or BR, promoted elongation growth to a greater degree at 50 than 100 μmol m−2 s−1 for petunia and calibrachoa. In addition to the promoted elongation growth, B and BRF reduced side branch number, biomass allocation to side branches, leaf epinasty, leaf angle, and/or leaf chlorophyll content relative to R or BR, but increased individual leaf area, petiole length, and/or biomass allocation to main stem, which varied with different species. It suggests that the promoted elongation growth by blue light associated with lower phytochrome activity is one of shade-avoidance responses with varying sensitivity among species.
Patel, J. S., Radetsky, L., & Rea, M. S. (2018). The Value of Red Light at Night for Increasing Basil Yield. Can. J. Plant Sci., in press.
Abstract: Sweet basil (<i>Ocimum basilicum L.</i>) is primarily used for culinary purposes, but it is also used in the fragrance and medicinal industries. In the last few years, global sweet basil production has been significantly impacted by downy mildew caused by <i>Peronospora belbahrii</i>. Nighttime exposure to red light has been shown to inhibit sporulation of <i>P. belbahrii</i>. The objective of this study was to determine if nighttime exposure to red light from light-emitting diodes (LEDs; λ<sub>max</sub> = 625 nm) could increase plant growth (plant height and leaf size) and yield (number and weight of leaves) in basil plants. In two sets of greenhouse experiments, red light was applied at a photosynthetic photon flux density (PPFD) of 60 µmol m<sup>-2</sup> s<sup>-1</sup> during the otherwise dark night for 10 hours (from 20:00 to 06:00). The results demonstrate that exposure to red light at night can increase the number of basil leaves per plant, plant height, leaf size (length and width), and leaf fresh and dry weight, compared to plants in darkness at night. The addition of incremental red light at night has the potential to be cost-effective for fresh organic basil production in controlled environments.
Palmer M, Gibbons R, Bhagavathula R, Holshouser D, & Davidson D. (2017). Roadway lighting's impact on altering soybeah growth: Volume 1. Illinois Center for Transportation, Research Report No. FHWA - ICT - 17 - 010.
Abstract: The impact of roadway lighting on soybean plant growth
was measured in
situ at seven locations in the state of
The plant data collection included periodic height,
, as well as plant moisture content and dried seed weight after harvest
The periodic measurements were made at the same locations over time to determine delays in plant development. The impact of roadway lighting trespass was significant and measurable above thresholds of both horizontal and vertical illuminance as well as a combination of the two. A specification was drafted to minimize the impact of roadway lighting trespass on the soybean, and countermeasures were recommended to control the impact of lighting on the soybean.