Gas exchange 2: plants: metabolism and photosynthesis are dependent on co2 and o2 exchange with the environment. Where are stomata: bottom of the leaf (more cool and humid, floating aquatic plants on surface, grasses: both, confers: rows on each side of needle. Stomata structure: grass stomata look like elongated dumbbells, shapes will vary based on leaf shape as well. How do stomata open and close: cellulose microfibrils ring around, extra water in cells increase turgor pressure, they (cid:272)a(cid:374)"t stret(cid:272)h out(cid:449)ards so they (cid:271)e(cid:272)o(cid:373)e (cid:271)e(cid:374)t a(cid:374)d are for(cid:272)ed to ope(cid:374) Why do the cells swell: water uptake driven by potassium influx, solute concentration increases; water flows into cell which increases turgor pressure, major players in opening stomata (especially number 2) Regulation of stomatal opening and closing: respond to internal co2 pressure, close in response to water stress, respond to light, have endogenous (diel) rhythms. C4 photosynthesis: evolution during period when photorespiration was really high, mesophyll carboxylase.