The sensitivity of photosynthesis to magnesium deficiency differs between rice (Oryza sativa L.) and cucumber (Cucumis sativus L.)

Xusheng Meng; Song Bai; Shiyu Wang; Yonghui Pan; Kehao Chen; Kailiu Xie; Min Wang; Shiwei Guo

doi:10.3389/fpls.2023.1164866

The sensitivity of photosynthesis to magnesium deficiency differs between rice (Oryza sativa L.) and cucumber (Cucumis sativus L.)

Front Plant Sci. 2023 Apr 14:14:1164866. doi: 10.3389/fpls.2023.1164866. eCollection 2023.

Authors

Xusheng Meng¹, Song Bai², Shiyu Wang¹, Yonghui Pan¹, Kehao Chen¹, Kailiu Xie^{1

3}, Min Wang¹, Shiwei Guo¹

Affiliations

¹ Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, The Key Laboratory of Plant Immunity, Nanjing Agricultural University, Nanjing, China.
² Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, China.
³ School of Land Resources and Environment, Jiangxi Agricultural University, Nanchang, China.

Abstract

Magnesium is an essential macronutrient for plant photosynthesis, and in response to Mg deficiency, dicots appear more sensitive than monocots. Under Mg deficiency, we investigated the causes of differing photosynthetic sensitivities in a dicot and a monocot species. Rice (Oryza sativa L.) and cucumber (Cucumis sativus L.) were grown in hydroponic culture to explore their physiological responses to Mg deficiency stress. Both Mg-deficient rice and cucumber plants exhibited lower biomass, leaf area, Mg concentration, and chlorophyll content (Chl) compared with Mg-sufficient plants. However, a more marked decline in Chl and carotenoid content (Car) occurred in cucumber. A lower CO₂ concentration in chloroplasts (C _c) was accompanied by a decrease in the maximum rate of electron transport (J _max) and the maximum rate of ribulose 1,5-bisphosphate carboxylation (V _cmax), restricting CO₂ utilization in Mg-deficient plants. Rice and cucumber photorespiration rate (P _r) increased under Mg deficiency. Additionally, for cucumber, Car and non-photochemical quenching (NPQ) were reduced under lower Mg supply. Meanwhile, cucumber Mg deficiency significantly increased the fraction of absorbed light energy dissipated by an additional quenching mechanism (Φf,D). Under Mg deficiency, suppressed photosynthesis was attributed to comprehensive restrictions of mesophyll conductance (g _m), J _max, and V _cmax. Cucumber was more sensitive to Mg deficiency than rice due to lower NPQ, higher rates of electron transport to alternative pathways, and subsequently, photooxidation damage.

Keywords: NPQ; cucumber; magnesium; photoprotection; photosynthesis; rice.

Grants and funding

This work was financially supported by the National Natural Science Foundation of China (32072673), the Young Elite Scientists Sponsorship Program by CAST (2018QNRC001), the Fundamental Research Funds for the Central Universities (KYGD202007), and the Innovative Research Team Development Plan of the Ministry of Education of China (IRT_17R56).