Photosynthetic performance of two coffee species under drought |
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Authors: | FM Da Matta M Maestri and RS Barros |
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Institution: | (1) Departamento de Biologia Vegetal, Universidade Federal de Vi?osa, 36571-000 Vi?osa, MG, Brazil |
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Abstract: | Coffea arabica cv. Red Catuaí and C. canephora cv. Kouillou were grown in pots beneath a plastic shelter. When they were 14
months old, irrigation was withheld until the leaf pre-dawn water potential was about -1.5 and -2.7 MPa (designated mild and
severe water stress, respectively). Under mild stress, net photosynthetic rate (PN) decreased mainly as a consequence of stomatal
limitations in Kouillou, whereas such decreases were dominated by non-stomatal limitations in Catuaí. Under severe drought,
further decreases in PN and apparent quantum yield were not associated to any changes in stomatal conductance in either cultivar.
Decreases were much more pronounced in Catuaí than in Kouillou, the latter maintained carbon gain at the expense of water
conservation. In both cultivars the initial chlorophyll (Chl) fluorescence slightly increased with no changes in the quantum
efficiency of photosystem 2. In response to rapidly imposed drought, the Chl content did not change while saccharide content
increased and starch content decreased. Photoinhibition and recovery of photosynthesis, as evaluated by the ratio of variable
to maximum fluorescence and by the photosynthetic O2 evolution, were unaffected by mild drought stress. Photoinhibition was
enhanced under severe water deficit, especially in Catuaí. In this cultivar the O2 evolution did not resume upon reversal
from photoinhibition, in contrast to the complete recovery in Kouillou.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | chlorophyll Coffea arabica Coffea canephora fluorescence kinetics gas exchange photoinhibition saccharides stomatal density and conductance transpiration water stress |
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