Effect of different concentrations of foliar iron fertilizer on chlorophyll fluorescence characteristics of iron-deficient rice seedlings under saline sodic conditions

• Published in: Plant physiology and biochemistry 2022-08, Vol.185, p.112-122
• Main Authors: Gao, Dapeng, Ran, Cheng, Zhang, Yunhe, Wang, Xiaolei, Lu, Sifei, Geng, Yanqiu, Guo, Liying, Shao, Xiwen
• Format: Article
• Language: English
• Subjects: Chlorophyll a fluorescence rise kinetics; Iron deficiency; JIP-Test; Reflection changes at 820 nm; Rice; Saline sodic stress
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2022.05.021

The effectiveness of iron is reduced in saline conditions, which can easily lead to iron deficiency and inhibit photosynthesis in rice. In this study, 4-week-old Fe-deficient rice seedlings were treated under saline sodic stress (50 mM) to different concentrations (0, 0.2%, 0.4%, 0.8%, 1.6%, and 3.2%) of foliar iron fertilizer (FeEDDHA). Differences in prompting fluorescence and the MR820 signal of rice leaves after 7 days of treatment were probed using the JIP-test. The results show that the performances of the two rice varieties were in general agreement. Under iron deficiency and soda salinity stress conditions, rice growth was inhibited, and the pigment content, specific energy flux, quantum yield, performance of the active PSII reaction center (PIABS) and the oxidation (Vox) and reduction rates (Vred) of PSI were reduced. These indicators first increase and then decrease with increasing iron fertiliser concentrations. The best results were obtained with the Fe3 treatment (0.8%). Fluorescence parameters such as the relative variable fluorescence (WK and VJ) and the quantum yield of energy dissipation (φDo) showed opposite trends. This suggests that iron deficiency/excess and soda saline stress disrupt the electron and energy transport in the photosystem. Appropriate iron fertilization concentration can repair the photosynthetic electron transport chain, improve electron transport efficiency and promote balanced energy distribution. Therefore, we suggest that moderate amounts of Fe are beneficial for improving the electron and energy transport properties of the photosystem, while spraying high concentrations of Fe fertilizer has a negative effect on improving salt tolerance in rice. •Combined saline and iron deficiency stresses cause greater damage to the donor side of PSII (WK) in rice seedlings.•Iron application can improve PSII light energy trapping (φPo) and transfer efficiency (φEo).•Iron spraying increased the rate of oxidation(Vox) and reduction(Vred) of P700 and PC.