荧光分析描述方法的好文章--Hydrogen_peroxide_production_is_an(6)

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Fig.7

The pattern of H2O2 production in guard cells of Arabidopsis thaliana as indi-cated by the Xuorescence of H2DCF-DA, in the Columbia wild type in the absence (con-trol) (a) or the presence of 2mMHCO3 (b) or

HCO3+DPI(20 M) (c) or H2O2 (10¡5M) (d). The pan-els f, g and h show the eVect of HCO3, HCO3+DPIandH2O2, respectively, on H2O2 production in guard cells of AtrbohD/F mutant. The panel e is control for mutant. Bar represents 25 m

Planta (2007) 225:1421–1429

in present study (Fig.1), is similar to the observationson stomatal conductance in response to varying CO2.The stomatal conductance was enhanced at CO2 con-centrations of <100ppm and stomata closed at CO2levels of >100ppm (Morison 1987; Raschke 1975).Thus, the present results of the present study indicatethat stomatal responses in epidermal strips to addedbicarbonate in the medium are similar to that of CO2,as observed earlier (Mrinalini etal. 1982).

The stomatal closure in response to CO2 was oftenstudied by bubbling CO2 into the medium where theepidermal strips are kept. We, however, have used theaddition of sodium bicarbonate as an alternative strat-egy. The concentration of bicarbonate that caused

stomatal closure (2mM) is equivalent to about 240 MCO2, calculated by using Henderson–Hasselbalch equa-tion (Hauser etal. 1995) taking into account the pH of7.2, bicarbonate concentration and assuming pKa valueof NaHCO3 as 6.28. This is rather high compared to theatmospheric levels of CO2. But the emphasis of our arti-cle is to point out the rise in H2O2 levels in guard cells asthey close in response to bicarbonate.

Bicarbonate induces H2O2 production in guard cellsDespite the extensive work done on the eVect of ele-vated CO2 on plants, the mechanism of perception andtransduction of the CO2 signal by guard cells is not

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