May function in depolymerizing pectin during pollen development, germination, and tube growth. Acts as an exo-polygalacturonase. [(1->4)-alpha-D-galacturonosyl](n) + H2O = [(1->4)-alpha-D-galacturonosyl](n-1) + alpha-D-galacturonate Pollen tubes growing through the style during pollination. Accumulates late in pollen development and/or during germination and tube growth. Belongs to the glycosyl hydrolase 28 family.