Growth and cell division of lettuce plants under various ratios of red to far-red light-emitting diodes

Abstract

We investigated the effects of various ratios of red to far-red light-emitting diodes (LEDs) on growth characteristics, physiological response, and cell division of red leaf lettuce. Sixteen-day-old lettuce seedlings were transferred into growth chambers and cultivated under various ratios of red (R) and far-red (FR) LEDs (R/FR = 0.7, 1.2, 4.1, and 8.6), only red LEDs (RED), or fluorescent lamps (control) for 22 days. Growth characteristics were measured at 11 and 22 days of treatment. In addition, cell division rate, epidermal cell density, chlorophyll fluorescence, and photosynthesis of leaves were analyzed. Fresh and dry weights and leaf area in all R/FR treatments were higher than those in the control at 22 days of treatment. The R/FR 1.2 had the highest values among R/FR treatments. The number of leaves appeared to increase as R/FR ratio increased. The specific leaf weights in the R/FR ratio of 0.7, 1.2, and 8.6 were similar to the control at 22 days of treatment. The SPAD values in all R/FR treatments were lower than that in the control. All R/FR treatments led to a longer leaf shape than the control. The percentage of cells in the G2M phase, indicating the cell division rate, increased in the R/FR treatments after 4 days of treatment, which supported the growth improvement in the R/FR treatments. The Fv/Fm and the photosynthetic rate in all treatments decreased due to the absence of blue light. The results of this study suggest that the supplementation with far-red LEDs should be considered when designing artificial lighting systems for closed-type plant factories since far-red light affects the vegetative growth of leafy vegetables such as lettuce.Additional key words: G2M phase, light quality, phytochromes, plant factory Hort.

Growth, Water-Use Efficiency, Stomatal Conductance, and Nitrogen Uptake of Two Lettuce Cultivars Grown under Different Percentages of Blue and Red Light

“…Our results show opposite trends between shoot dry mass and SPAD index ( Figures 2D and 3C). Similar to our findings, others have reported a reduction in chlorophyll concentration with higher lettuce growth based on either non-destructive measurements of leaf greenness (e.g., SPAD index) or chlorophyll extraction [47][48][49]. The increase in SPAD index with higher blue light could be attributed to a reduction in plant growth, which has been shown to lead to an accumulation of higher chlorophyll content on a per-unit leaf mass basis and/or a potential increase in chlorophyll biosynthesis [9].…”

The Growth and Development of ‘Mini Chal’ Tomato Plug Seedlings Grown under Various Wavelengths Using Light Emitting Diodes

“…Low R/Fr ratio induced a higher Fv/Fm value in plants than R3B7. These results were similar to those of chlorophyll fluorescence 11 days after treatment in lettuce treated with R/Fr ratios of 0.7, 1.2, 4.1 and 8.6 [91].…”

Influence of Wavelength of Light on Growth, Yield and Nutritional Quality of Greenhouse Vegetables

“…Greenhouse vegetable yield is influenced by different light colours (Table 2). Fresh weight of lettuce, baby leaf lettuce and red leaf lettuce was observed to increase under additional far red lighting (Li and Kubota, 2009;Stutte et al, 2009;Lee et al, 2015;Chen et al, 2016;Lee et al, 2016;Pinho et al, 2017).…”

“…Far red lighting increases growth of lettuce (Lee et al, 2016;Pinho et al 2017). It elongates leaves in baby leaf lettuce (Li and Kubota, 2009), red lettuce (Lee et al, 2015) and in red leaf lettuce (Stutte et al, 2009) resulting in taller plants (Brown et al, 1995). Additional red light was observed to delay or inhibit transition to flowering in basil (Tarakanov et al, 2012).…”