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Canola (Brassica napus L.) enhances NaCl and high concentrations of sodium ions tolerance by maintaining ion homeostasis, higher antioxidant enzyme activity and photosynthetic capacity fluorescence parameters

Lupeng Sun, Xiaoqiang Cao, Juncan Du, Yan Wang, fenghua Zhang

Abstract

Under salt stress, plants are forced to take up and accumulate large amounts of Na+ and Cl-, but most of the current studies have focused on the toxic effects of Na+ on plants, and the effects of Cl- stress on plants are also very important but often neglected. And the mechanisms of growth physiology of canola varieties with different salt tolerance in response to these three salts are still unclear. To investigate the growth physiological response of different canola varieties with salt tolerance to Na+, Cl- and NaCl stress. Short-term (12 h) equimolar (150 mM) concentrations of Na+, Cl-, and NaCl stresses were applied to salt-tolerant and sensitive canola varieties using hydroponic experiments. NaCl treatment caused the strongest damage to both canola varieties, and stress damage was more severe at high concentrations of Na+ than Cl-. High concentrations of Cl- treatment could promote the uptake of ions (K+, Ca2+) and induce antioxidant defense system (SOD enzyme activity) response in canola to some extent. Na salts treatment, the fresh dry weight of roots and stems and leaves of Huayouza 62 was significantly greater than that of Xiangyou 15. The effects of different types of salt treatments on the maximum quantum yield of photochemical reactions in photosystem II (Fv/Fm) and the ratio of photochemical to non-photochemical processes in PSII (Fv/Fo) of Huayouza 62 were not significant; and the Mg2+ content, Mg2+/Na+, the maximum quantum yield of photochemical reactions in photosystem II and the ratio of photochemical to non-photochemical processes in PSII of Huayouza 62 were significantly higher than those of Xiangyou 15 when treated with NaCl and Na salts. In summary, both NaCl and Na salts treatments inhibited the growth of canola seedlings, and salt-tolerant varieties were able to mitigate ion toxicity by maintaining lower Na+ content in the root system for a short period of time, higher Mg2+ content, Mg2+/Na+, and antioxidant enzyme activity to improve photosynthetic capacity, and subsequently re-establish a new K+/Na+, Ca2+/Na+ balance to improve their salt tolerance. High concentrations of Cl salts caused not only lower damage to canola seedlings than NaCl and Na salts, but also Cl- had a positive role in inducing oxidative stress and responsive antioxidant defense in canola seedlings in the short term.

FP23089  Accepted 08 July 2024

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