02035nas a2200133   4500008004100000245010100041210006900142300001500211490000700226520159400233100001401827700002001841856004001861       1993                        eng d00aPhotosynthetic and stomatal responses of Avena sativa  (Poaceae) to a variable light environment0 aPhotosynthetic and stomatal responses of Avena sativa Poaceae to  a1369 -13730 v803 aThe net photosynthetic (A), stomatal conductance to water vapor (g), water use efficiency (WUE = A/transpiration), and leaf water potential (Ψ) responses of cultivated oats (Avena sativa) were determined under an experimental regime of alternating full sun (photosynthetic photon flux density, PPFD > 1,700 μmol·m-2·sec-1) and shade (300-400 μmol·m-2 sec-1 PPFD). Less extensive measurements were made on winter wheat (Triticum aestivum) to test the generality of crop species' responses. The rates of stomatal opening/closing after changes in PPFD in Avena and Triticum were compared with previously determined rates for native grasses and forbs to assess how domestication might have altered stomatal dynamics. Characteristics of Avena under alternating sun and shade were 1) rapid fluctuations in A between full sun (∼27 μmol·m-2 sec-1) and shade rates (∼12-13 μmol m-2·sec-1); 2) slower changes in g, causing progressive stomatal closure during the measurement sequence and possible stomatal limitation of A; 3) no change in leaf Ψ; and 4) a net reduction in WUE. Triticum had similar sun/shade A, g, and WUE dynamics, except that Triticum stomata returned to full-sun g between shade periods. The rates of change of g in Avena and Triticum were lower than for some desert and subalpine native species, but were similar to rates for species in adjoining native habitat. The basic stomatal dynamics of Avena and Triticum may typify many cultivated C3 species, and these data indicate that crop stomatal behavior has not diverged significantly from that of native species.1 aFay, P.A.1 aKnapp, Alan, K.  uhttp://www.jstor.org/stable/2445664