Protein kinase involved in salt tolerance and pH sensitivity, probably by regulating plasma membrane potential and cation influx. Positively controls the TRK1 potassium transport system in response to potassium starvation. Stabilizes plasma membrane nutrient transporters in the plasma membrane by preventing their vacuolar sorting and degradation (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. NPR/HAL subfamily. HAL5 sub-subfamily.