Low red/far-red ratio as a signal promotes carbon assimilation of soybean seedlings by increasing the photosynthetic capacity

Abstract

Background: Shading includes low light intensity and varying quality. However, a low red/far-red (R/Fr) ratio of light is a signal that affects plant growth in intercropping and close-planting systems. Thus, the low R/Fr ratio uncoupling from shading conditions was assessed to identify the effect of light quality on photosynthesis and CO 2 assimilation. Soybean plants were grown in a growth chamber with natural solar radiation under four treatments, that is, normal (N, sunlight), N + Fr, Low (L) + Fr, and L light. Results: Low R/Fr ratio significantly increased the total biomass, leaf area, starch and sucrose contents, chlorophyll content, net photosynthetic rate, and quantum efficiency of the photosystem II compared with normal R/Fr ratio under the same light level (P < 0.05). Proteomic analysis of soybean leaves under different treatments was performed to quantify the changes in photosynthesis and CO 2 assimilation in the chloroplast. Among the 7834 proteins quantified, 12 showed a > 1.3-fold change in abundance, of which 1 was related to porphyrin and chlorophyll metabolism, 2 were involved in photosystem I (PS I), 4 were associated with PS II, 3 proteins participated in photosynthetic electron transport, and 2 were involved in starch and sucrose metabolism. The dynamic change in these proteins indicates that photosynthesis and CO 2 assimilation were maintained in the L treatment by up-regulating the component protein levels compared with those in N treatment. Although low R/Fr ratio increased the photosynthetic CO 2 assimilation parameters, the differences in most protein expression levels in N + Fr and L + Fr treatments compared with those in N treatment were insignificant. Similar trends were found in gene expression through quantitative reverse transcription polymerase chain reaction excluding the gene expression of sucrose synthase possible because light environment is one of the factors affecting carbon assimilation.Conclusions: Low R/Fr ratio (high Fr light) can increase the photosynthetic CO 2 assimilation in the same light intensity by improving the photosynthetic efficiency of the photosystems.

Effects of red to far-red light ratio on growth and photosynthetic characteristics of tomato seedlings under calcium nitrate stress

“…These results indicated that lower R:FR ratios treatments can decrease salt-induced inhibition of the PSII electron transport and improve salt tolerance of tomato seedlings, which is consistent with the results of Shu et al (2013) and Wang et al (2018). Similarly, Yang et al (2020) also reported that under the same illumination conditions, a low R:FR ratio treatment significantly improved the quantum yield of PSⅡ, which was consistent with the results of this experiment.…”

“…However, under low R:FR ratios treatments, the photosynthetic gas-exchange parameters of both salt-stressed and nonstressed plants increased. Yang et al (2020) reported a low R:FR light treatment increased the net photosynthetic rate of soybean leaves. Another report by Wang et al (2021) showed that a low R:FR light treatment enhanced the net photosynthetic rate of tomato leaves under NaCl stress.…”

Duration of Weed Presence Influences the Recovery of Photosynthetic Efficiency and Yield in Common Bean (Phaseolus vulgaris L.)

“…Interestingly, we found that PSII increased with longer duration of weed presence throughout the vegetative stages of common bean and declined rapidly, when weed competition extended to reproductive phases (Figure 8), while A n declined (Figure 5). In the absence of a decrease in PPFD, Fr light has been shown to increase PSII , A n , and overall photosynthetic capacity in soybean (Yang et al, 2020). Similarly, the addition of Fr light to shorter wavelengths increased photosynthetic efficiency across diverse taxa (Zhen and Bugbee, 2020).…”

“…The concurrent declines in A n , PSII and J as well as the restriction on V c,max could be evidence of oxidative stress due to an imbalance in energy distribution between the photosystems from reflected Fr light. Several studies have demonstrated Fr light-mediated improvements to photosynthetic capacity, when Fr light is supplied during vegetative growth (Park and Runkle, 2017;Zhen and van Iersel, 2017;Yang et al, 2020). If, however, neighboring weeds reflecting Fr light increase ROS production in common bean during vegetative growth, the conclusion of the CPWC and transition to reproductive growth may be a tipping point following which ROS start to directly impact photosynthetic activity.…”

Parental Shading Regulates Subsequent Seed Germination

“…Among the diverse environmental factors influencing seed germination, light is attractive, which not only acts as an energy resource, but also the molecular signal for initiating seed germination (Wang and Lin, 2020 ). It is known that close planting leads plants to perceive the shade signal, characterized with the decrease of blue light intensity and the red (R): far-red (FR) ratio, caused by neighboring plants (Keuskamp et al, 2011 , 2012 ; de Wit et al, 2012 ; Jiang et al, 2019 ; Zhang et al, 2019 ; Yang et al, 2020 ). In close planting conditions, competition for light triggers the plant shade response, including the change of flowering time, promotion of stem and petiole elongation, regulation of seed maturation, variation in photosynthetic response, and decrease of crop productivity (Kurepin et al, 2006 ; Jha et al, 2010 ; Elwell et al, 2011 ; Baker et al, 2018 ; Chai et al, 2018 ; Pantazopoulou et al, 2021 ).…”