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Ozone-induced changes in CO2 assimilation, O2 evolution and chlorophyll a fluorescence transients in barley

1989; Elsevier BV; Volume: 59; Issue: 2 Linguagem: Inglês

10.1016/0269-7491(89)90101-2

1873-6424

A.J. Rowland-Bamford, Steven E. Coghlan, Peter J. Lea,

Plant Water Relations and Carbon Dynamics

Spring barley (Hordeum vulgare cv. Klaxon) plants, 9 days old, were exposed to 0.05, 0.10 or 0.15 μl litre−1 ozone (O3) for 12 days. Fumigation was administered for 7 h between 9.00 h and 16.00 h each day. Using conventional IRGA equipment, the carbon dioxide exchange rate (CER) was shown to decrease with increasing concentration of O3 during the exposure period, falling to 60% of the control value at the highest O3 concentration. Transpiration rates and stomatal conductance showed similar trends. Light saturation curves, obtained using a leaf disc oxygen electrode, demonstrated that O3-treated leaves had lower apparent quantum yields (QY) and generally lower rates of O2 evolution at saturating light and CO2 levels. Oscillations in chlorophyll a fluorescence, normally observed in control plants, could not be detected after O3 treatment and could only be restored to some extent by feeding the phosphate sequestering agent d-mannose to the leaves.