Tip growth is a specialized cell growth characterized by extremely rapid, polarized cell extension. Both plants and fungi exhibit tip growth, including the elongating pollen tubes necessary for fertilization and the filamentous protonemata that begin the haploid moss life cycle. The regulation of pollen tube growth relies on the flux of both cations and anions near the tip, or apex, of the growing pollen tube which is correlated with oscillations in the growth rate. Stretch-activated cation channels have been observed at the apex, but there is currently little understanding of the mechanism behind known Cl- fluxes. Our group proposes that an A. thaliana homolog of the bacterial mechanosensitive ion channel, MscS-Like 8 (MSL8), is an apex-localized stretch-activated Cl- channel that regulates Cl- flux in growing pollen tubes. We are using the model moss P. patens to further explore the role of mechanosensitive ion channels in tip growth by interfering with MscS homologs expressed in moss and expressing homologs from A. thaliana. We aim to uncover novel regulatory roles for mechanosensitive channels in this specialized cell growth system.