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

Secondary soil salinization causes plant stress, which can be relieved by different ratios of red to far-red light (R:FR). Our study aimed to elucidate the role of low R:FR ratios treatments on photosynthesis and growth of tomato seedlings in salinized soils. Tomato seedlings were treated under three R:FR ratios and calcium nitrate was applied simultaneously. The results showed that the treatments under low R:FR ratios stimulated growth parameters of tomato seedlings under calcium nitrate stress, the best impact being achieved at the R:FR ratio of 0.7 in this experiment. Low R:FR ratios treatments increased proline content as well as PSII maximum efficiency, actual electron transport operating efficiency, and photochemical quenching of tomato seedlings under calcium nitrate stress but decreased the value of nonphotochemical quenching. Moreover, low R:FR ratios treatments promoted net photosynthetic rate and increased the expression of a Rubisco gene. In conclusion, low R:FR ratios treatments could improve the salt resistance of greenhouse tomato plants.

Automated summary

The study demonstrated that treatment with low R:FR ratios can enhance the growth and photosynthesis of tomato seedlings under secondary soil salinization, thereby improving their salt resistance. The most effective treatment was found at an R:FR ratio of 0.7, which significantly increased proline content, photosynthetic efficiency, and gene expression related to photosynthesis.