Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage

Abstract

Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. “Zhongshuang 11”) to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B%, and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm−2s−1. With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (Pmax), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (Pn). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low Fv/Fm (photosynthetic maximum quantum yield) and a high content of O2.- and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low photonflux. Under different R:B photonflux ratios, red and blue lights may play mutual roles in Pn. When the blue light dominated, the Pn showed a B-preference. When the red light dominated, the Pn showed an R-preference. Furthermore, CLs were suitable for the Pn of rapeseed seedlings.

Impacts of LED spectral quality on leafy vegetables: Productivity closely linked to photosynthetic performance or associated with leaf traits?

“…Plants grown under 0B, 50B and 100B conditions had similar lower values of shoot, root FW and DW (Figure 3). Our results of ice plants agree with the finding from many other studies that supplementing optimal amount of blue light to red light is necessary to achieve greater biomass accumulation [18,21,29,39,61,62] . However, similar to the 0B condition the stronger blue-LEDs such as 50B and 100B resulted in reduction of biomass accumulation in ice plant (Figure 3).…”

“…Compared to R-LED alone (0B), all combined RB-LEDs promote leaf growth and development, dry matter accumulation and photosynthesis of Chinese broccoli ( Figure 1 and Table 1). These results support the notion that for certain species any level of blue light regulates leaf development and photosynthetic performance [18,36] . In other words, blue light alleviate "red light syndrome" such as a low photosynthetic rate, low LMA, unresponsive stomatal conductance and impaired shoot and root growth [7,36,39,51] .…”

“…In addition to red light, many studies have manipulated the proportion of blue light necessary for normal plant growth [13,15,16,39,48] . Supplementing appropriate amount of blue light to red light results in dramatic effects on the morphology and anatomy structure [13,18,23,[48][49][50] , chloroplast structure [31,48,51,52] and photosynthetic performance [18,36,39,[53][54] .…”

Plant Growth and Photosynthetic Characteristics of Mesembryanthemum crystallinum Grown Aeroponically under Different Blue- and Red-LEDs

“…Yield of lettuce, spinach, and radish crops grown under appropriate combination of red and blue light was enhanced compared to red light alone (Yorio et al, 2001). Similar results were found in strawberry plantlet (Nhut et al, 2003), rapeseed ( Brassica napus L.) plantlets in vitro (Li et al, 2013), rapeseed rosette leaves (Shengxin et al, 2016), and cucumber seedlings (Hernández and Kubota, 2016; Trouwborst et al, 2016). In a recent developed highly energy-efficient laser-illuminated growth chamber, Ooi et al (2016) also showed that the application of diffused single-wavelength red and blue laser light is adequate for the growth and development of Arabidopsis thaliana .…”

“…It was observed that lettuce and other dicotyledonous plants developed excessive hypocotyl and stem elongation, leaf extension, and reduced chlorophyll (Chl) when grown under red-LED as the sole source of irradiation. The abnormal morphological characteristics were eliminated when red-LED was supplemented with blue light (Bula et al, 1991; Yorio et al, 2001; Nhut et al, 2003; Li et al, 2013; Hernández and Kubota, 2016; Shengxin et al, 2016; Wang et al, 2016). Yield of lettuce, spinach, and radish crops grown under appropriate combination of red and blue light was enhanced compared to red light alone (Yorio et al, 2001).…”