Abstract
Summary We studied the sequential effect of simulated acid rain (SAR) and water stress on net photosynthesis (A), internal CO 2 concentration ( Ci ), stomatal conductance (g), and instantaneous water use efficiency (A/E), and the photochemical damage caused by these stressors by analysing chlorophyll fluorescence parameters such as Fv/Fm, Fv/Fo and Fm/Fo. SAR caused inhibition of photosynthesis. The depletion of CO 2 assimilation seems not to be solely a stomatal effect as effects on chloroplasts contribute to this photosynthetic inhibition. No noticeable damage seems to occur to the photochemical apparatus since well-watered plants treated with acid rain did not show any change in the chlorophyll fluorescence. Water stress produced a large effect on both gas exchange and chlorophyll fluorescence parameters, indicating structural and functional damage. Interactions among SAR and drought had a larger impact on all parameters studied. However, after rewatering, significant recovery in both gas exchange and chlorophyll fluorescence parameters occurred within 6 days, although the values measured prior to the imposition of treatments were not recovered. We conclude that Pinus radiata exposed to acid rain were affected in a wide range of components in the photosynthetic apparatus, thereby modifying its response to sequential drought stress.
Published Version
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