During the in vitro germination of pear pollen, several hydrolases were released into the medium. They were apparently eluted from the pollen grain, since the activity was the same when germination was inhibited. These enzymes, once released, had no role in tube growth, since resuspension of pollen in fresh medium after 1.5 hr of incubation did not result in a change of the subsequent tube growth. Homogenates of the pollen suspension at different stages of development showed no significant changes in phosphatase, β-glucosidase, or β-galactosidase activity. However, patent β-glucosidase activity measured directly in suspensions of intact pollen did increase after germination in proportion to tube wall development. Nojirimycin, a specific inhibitor of glucosidases, reduced this β-glucosidase activity by 75% at 10−5M and significantly reduced growth rate at 10−4
