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Changes in photon flux can induce stomatal patchiness

Eckstein, J., Beyschlag, W., Mott, K.A., Ryel, R.J.
Plant, cell and environment 1996 v.19 no.9 pp. 1066-1074
Helianthus annuus, Xanthium strumarium, Aesculus hippocastanum, stomatal conductance, fluorescence, Ocimum basilicum, light intensity, water stress, Malus, spatial variation, stomata, chlorophyll, Arbutus unedo, Acer platanoides, leaf conductance
Images of chlorophyll fluorescence were used to detect the occurrence of stomatal patchiness in leaves from eight species under variable photon flux conditions. Pronounced stomatal patchiness was induced within 5-10 min after PFD was changed from intermediate (approximately 450 micromole quanta m-2 s-1) to low (approximately 150 micromole quanta m-2 s-1) levels. This effect was completely reversible by returning PFD to intermediate levels. The pattern of heterogeneous fluorescence for each leaf was usually similar during repeated applications of medium and low PFD. In three species, stomatal patchiness could only be induced in slightly water-stressed plants. Leaves of more severely waterstressed Xanthium strumarium plants in low air humidity exhibited oscillations in fluorescence that corresponded with oscillatory changes in leaf diffusion conductance for water vapour. Stomatal patchiness was also induced by illuminating dark-adapted leaves with low PFD (below 200-300 micromole quanta m-2 s-1). Infiltration of leaves with distilled water showed that heterogeneous chlorophyll fluorescence was caused by changes in stomatal apertures.