pleiotropic gene, 1139 ploidy, 1139 plug-flow in catalysis, 1139 plumbylenes [obsolete] , 1140 plumbylidenes, 1140 plume in atmospheric chemistry, 1140 plus, minus, 1140 pneumatic detector, 1140 point group, 1141 point of zero charge (p.z.c.), 1141 poise , 1141 poison in catalysis , 1141