On-line version ISSN 1678-4499
KONRAD, Maria Luiza Freitas; SILVA, José Aliçandro Bezerra da; FURLANI, Pedro Roberto and MACHADO, Eduardo Caruso. Gas exchange and chlorophyll fluorescence in six coffee cultivars under aluminum stress. Bragantia [online]. 2005, vol.64, n.3, pp. 339-347. ISSN 1678-4499. http://dx.doi.org/10.1590/S0006-87052005000300004.
Experiments were carried out under greenhouse and growth chamber to evaluate the effects of aluminum (Al) on several photosynthetic characteristics in six coffee cultivars. Plants were grown in nutrient solution aerated continuously, containing two Al concentration, 0 and 0.148 mmol L-1, supplied as Al2(SO4)3. After 97 days of treatament, measurements of CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (gs), internal CO2 concentration (Ci), instantaneous carboxylation efficiency (Fc) and chlorophyll fluorescence related characteristics were performed. All six cultivars showed decrease in A, gs and Fc and increase in Ci. The basal chlorophyll fluorescence yield (Fo) increased and the maximum quantum efficiency (Fv/Fm) decreased suggesting structural damage in thylakoid. The photosynthetic induction curve revealed that Al caused decreases in photochemical quenching of fluorescence as well as increases of non-photochemical quenching. Our results indicated that A reduction was related to decreases in both stomatal conductance, and biochemical and photochemical damages.
Keywords : Coffea arabica; aluminum toxicity; photosynthesis; stomatal conductance; photosynthesis induction.