Abstract
BACKGROUND: This study explored the pivotal role of exogenous plant growth regulators in enhancing salt tolerance in rice. The underlying regulatory mechanisms of gibberellin (GA₃) and prohexadione-calcium (Pro-Ca) under NaCl stress remain unclear. The salt tolerant variety Guanghong 3 (GH3) and the salt-sensitive variety FL478 were used as experimental materials to examine the effects of NaCl (80 mM) stress. This study explored the mitigating effects of foliar application of gibberellin (GA₃) and prohexadione calcium (Pro-Ca) on plant growth, carbon metabolism, and cellular energy metabolism in rice seedlings under NaCl stress. RESULTS: Foliar application of GA₃ and Pro-Ca significantly restored rice morphogenesis under NaCl stress. Pro-Ca application significantly enhanced root development in GH3 and FL478 by 15.67% and 8.65%, respectively. GA₃ primarily promoted shoot growth, increasing plant height by 10.04% in GH3 and 12.32% in FL478. Regarding energy metabolism, Pro-Ca increased root ATP content by 23.11% and energy charge by 5.78% in GH3, while in FL478, it elevated root ATP by 7.03%. In contrast, GA₃ raised leaf ATP content by 7.19% in GH3. Regarding carbon metabolism, Pro-Ca effectively enhanced sucrose content by 25.99% and sucrose phosphate synthase activity by 35.67% in FL478. GA₃ showed significantly improved photosynthetic rate by 56.08% and photochemical efficiency by 26.25% in GH3. CONCLUSIONS: The results demonstrated that Pro-Ca and GA₃enhanced salt tolerance in rice by differentially regulating energy metabolism and carbon metabolism. FL478 exhibited a stronger response to Pro-Ca’s optimization of root energy metabolism, whereas GH3 showed greater sensitivity to GA₃’s maintenance of shoot energy status. These findings provide a theoretical basis for using exogenous regulators like Pro-Ca and GA₃ to enhance rice productivity in saline-alkali soils.