Exogenous Strigolactones alleviate KCl stress by regulating photosynthesis, ROS migration and ion transport in Malus hupehensis Rehd.

ABSTRACT

AIMS: In recent years, the application of large amounts of potash fertilizer in apple orchards leads to worsening KCl stress. Strigolactone (SL), as a novel phytohormone, reportedly participates in plant tolerance to NaCl and drought stresses. However, the underlying mechanism and the effects of exogenous SL on the KCl stress of apple seedlings remain unclear. METHODS: We sprayed different concentrations of exogenous SL on Malus hupehensis Rehd. under KCl stress and measured the physiological indexes like, photosynthetic parameter, content of ROS, osmolytes and mineral element. In addition, the expressions of KCl-responding genes and SL-signaling genes were also detected and analyzed. RESULTS: Application of exogenous SL protected the chlorophyll and maintained the photosynthetic rate of apple seedlings under KCl stress. Exogenous SL strengthened the enzyme activities of peroxidase and catalase, thereby eliminating reactive oxygen species production induced by KCl stress, promoting the accumulation of proline, and maintaining osmotic balance. Exogenous SL expelled K+ outside of the cytoplasm and compartmentalized K+ into the vacuole, increased the contents of Na+, Mg2+, Fe2+, and Mn2+ in the cytoplasm to maintain the ion homeostasis under KCl stress. CONCLUSIONS: Exogenous SL can regulate photosynthesis, ROS migration and ion transport in apple seedlings to alleviate KCl stress.