Low red to far-red light ratio promotes salt tolerance by improving leaf photosynthetic capacity in cucumber

Abstract

Soil salinity severely inhibits leaf photosynthesis and limits agricultural production. Red to far-red light ratio (R/FR) affects leaf photosynthesis under salt stress, however, its regulation mechanism is still largely unknown. This study investigated the effects of different R/FR on plant growth, gas exchange parameters, photosynthetic electron transport, Calvin cycle and key gene expression under salt stress. Cucumber seedlings were exposed to four treatments including 0 mM NaCl and R/FR=7 (L7, control), 0 mM NaCl and R/FR=0.7 (L0.7), 80 mM NaCl and R/FR=7 (H7) and 80 mM NaCl and R/FR=0.7 (H0.7) for 9 days in an artificial climate chamber. The results showed that compared to L7 treatment, H7 treatment significantly reduced relative growth rate (RGR), CO2 assimilation rate (Pn), maximum photochemical efficiency PSII (Fv/Fm), most JIP-test parameters and total Rubisco activity, indicating that salt stress severely inhibited photosynthetic electron transport from PSII to PSI and blocked Calvin cycle in cucumber leaves. However, these suppressions were effectively alleviated by low R/FR addition (H0.7 treatment). Compared to H7 treatment, H0.7 treatment significantly increased RGR and Pn by 209.09% and 7.59%, respectively, enhanced Fv/Fm, maximum quantum yield for primary photochemistry (φPo), quantum yield for electron transport (φEo) and total Rubisco activity by 192.31%, 17.6%, 36.84% and 37.08%, respectively, and largely up-regulated expressions of most key genes involved in electron transport and Calvin cycle. In conclusion, low R/FR effectively alleviated the negative effects of salt stress on leaf photosynthesis by accelerating photosynthetic electron transport from PSII to PQ pool and promoting Calvin cycle in cucumber plants. It provides a novel environmentally friendly light-quality regulation technology for high efficiency salt-resistant vegetable production.

Effects of Four Photo-Selective Colored Hail Nets on an Apple in Loess Plateau, China

“…It is important to note that earlier studies have underlined the importance of a low red to far-red (R/FR) ratio in governing plant growth. This not only stimulates an enlargement of the cell wall, leading to an increase in leaf area, but also improves leaf photosynthetic capacity, dry matter accumulation, and overall plant growth [46][47][48]. Our research affirms these findings, as it revealed an increase in leaf area and a reduction in leaf thickness under blue net, suggesting that these are adaptive responses for shaded leaves to maximize light transmission to the chloroplasts.…”

Low Red to Far-Red Light Ratio Promoted Growth and Fruit Quality in Salt-Stressed Tomato Plants Based on Metabolomic Analysis

“…Carbohydrate is a key indicator of fruit sweetness and is also related to fruit quality, such as firmness and volatile aroma [33]. Numerous studies proved that under salt stress, low R/FR significantly promoted leaf photosynthesis and carbohydrate accumulation in cucumber plants [17]. Consistent with this, our study illustrated that low R/FR significantly increased TSS and soluble sugar contents in tomato fruit under salt stress (Na+L vs. Na, Figure 5).…”

“…Wang et al [16] suggested that low R/FR benefited the increase in salt tolerance in tomato plants mainly through increasing SOD, POD and CAT contents and decreasing H 2 O 2 contents. Miao et al [17] found that low R/FR improved cucumber photosynthetic efficiency through enhancing the photosynthetic electron transfer rate and Calvin cycle, effectively alleviating the negative regulations of salt stress. Hayes et al [18] indicated that under low R/FR irradiation, PIFs up-regulated the expression of the BSK5 gene and induced auxin signaling, finally accelerating hypocotyl elongation in salt-stressed Arabidopsis.…”

Impact of Different Red/Far-Red Light Ratios on the Morphological Changes and Nutritional Profile of Green Leafy Vegetable Choy Sum

“…Adjusting the ratio of R/FR has also been shown to impact photosynthetic efficiency and flowering responses in both short-day and long-day plants, providing a means to control plant morphology architecture. − The response occurs at both the plant level and the molecular level, with adjustments in photosynthetic electron transport and the path of light energy . Exposure to low ratios of R/FR was also found to improve the salinity tolerance in tomato seedlings and cucumber. , …”

“…4 Exposure to low ratios of R/FR was also found to improve the salinity tolerance in tomato seedlings and cucumber. 14,15 Different ratios of R/FR can have an impact on the bioactive compounds in green leafy vegetables that are beneficial to humans, such as carotenoids, anthocyanins, flavonoids, antioxidants, and minerals, 5,16,17 but the effects on these nutritional constituents have been explored finitely and conflictingly. For example, an increasing FR intensity was reported to improve the bioactive compounds in lettuce.…”