Regulation of Photosynthetic Capacity and Ion Metabolism of Oilseed Rape under Salt Stress by Prohexadione-Calcium Priming

Abstract

To investigate the effect of prohexadione-calcium (Pro-Ca) primed on seed germination and seedling growth of oilseed rape under salt stress, to alleviate the inhibition of soil salinization on the growth of oilseed rape, and to improve the sustainability of agricultural production. Using Huayouza 158R and Huayouza 62 as test materials, the regulation of seed germination and seedling growth under the stresses of 0, 100, and 150 mM NaCl (S0, S100, and S150) was investigated after the primed of Pro-Ca. We conducted six treatments, S0: non-primed + 0 mM NaCl, PCS0: Pro-Ca primed + 0 mM NaCl, S100: non-primed + 100 mM NaCl, PCS100: Pro-Ca primed + 100 mM NaCl, S150: non-primed + 150mM NaCl, Pro-Ca+S150: Pro-Ca primed + 150 mM NaCl. The results showed that salt stress inhibited seed germination and seedling growth, and Pro-Ca primed significantly increased the germination index and vigor index of oilseed rape seeds. The average germination time and malondialdehyde (MDA) content were significantly reduced, which resulted in the optimal initiation fiddling concentration of 8mg·L-1. The morphological parameters of oilseed rape decreased significantly under salt stress, with leaf area decreasing by 70.69% and 75.03% and total chlorophyll content decreasing by 18.55% and 18.68% at S150. With the rise of salt stress, the changes of each photosynthetic parameter were somewhat similar, and Pn, Gs, Ci, and Tr continued to decline, indicating that the effects of salt stress on photosynthesis in oilseed rape might be mainly attributed to stomatal restriction and inhibition of photosynthetic pigment synthesis. While Na+ and MDA contents increased significantly, reaching a peak at S150, indicating that Na+ content increased significantly under salt stress, which resulted in the slow growth of oilseed rape and weak plants under the influence of Na+ salt damage. After Pro-Ca primed, leaf area and photosynthetic pigment synthesis increased, and the initiation treatment promoted the rise of Pn, Gs, Ci, and Tr under salt stress. The Na+ content decreased by 7.29% and 6.96% in PCS100 compared with S100, decreased by 9.23% and 25.02% in PCS150 compared with S150, and increased in K+ and Mg2+ after Pro-Ca primed. At this time, the antioxidant enzyme activities increased, and the MDA content and relative conductivity decreased. It was concluded that Pro-Ca primed improved the photosynthetic capacity of oilseed rape by promoting leaf growth, stomatal opening, and photosynthetic pigment synthesis. At the same time, reducing Na+ content and promoting K+ and Mg2+ absorption and antioxidant enzyme activities together alleviate salt damage and improve salt tolerance of oilseed rape.