Dimethyl sulfoxide: reversible inhibitor of pollen tube growth.

Five percent dimethyl sulfoxide (DMSO) completely inhibited tube initiation, stopped tube growth and suppressed the high respiration associated with tube growth of lily pollen. The effect of DMSO on respiration was indirect because uncoupling concentrations of 2,4-dinitrophenol abolished the inhibition of respiration. Five percent DMSO did not inhibit rapid starch synthesis during the first 30 minutes of incubation, nor did DMSO inhibit the period of high respiration associated with rapid starch synthesis. DMSO did not cause permanent damage to the cells since normal pollen tube growth occurred after its removal. Dimethyl sulfoxide is not a general inhibitor of pollen metabolism, but it may be a specific inhibitor of a process required for tube growth.