Mechanosensitive channel that opens in response to stretch forces in the membrane lipid bilayer. Exhibits a 6.3-fold preference for chloride over sodium. Regulates osmotic forces during pollen hydration and germination. Not regulated by MgCl(2), ruthenium red or tetramethylammonium-Cl. Has a unitary conductance of 57 pS under negative membrane potentials and 39 pS under positive membrane potentials, and a gating threshold pressure of -48.2 mm Hg. Expressed in tricellular and mature pollen, and in germinating tube. Not detected in leaves or roots. No visible morphological defects in the coat or cell wall of desiccated pollen grains, but strongly decreased viability during rehydration. Belongs to the MscS (TC 1.A.23) family.