Calcium influx is required for the initiation of the hypersensitive response of Triticum aestivum to Puccinia recondita f.sp. tritici

With potassium pyroantimonate precipitation method, we investigated calcium distribution and cell ultrastructural changes in wheat leaves invaded by leaf rust fungi. The results showed that electron-densed calcium precipitates were located mainly at intercellular spaces and in the vacuoles under resting conditions. After inoculation, extracellular calcium moved toward the cytoplasm across the cell wall and the plasma membrane in both resistant and susceptible wheats. But calcium influx initiated at about 8 h after the leaf rust challenge in incompatible combinations which took place prior to compatible combinations for at least 4 h.