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PENA-OLMOS, Jaime E.  and  CASIERRA-POSADA, Fánor. Photochemical efficiency of photosystem II (PSII) in broccoli plants (Brassica oleracea var Italica) affected by excess iron. Orinoquia [online]. 2013, vol.17, n.1, pp.15-22. ISSN 0121-3709.

Acompletely randomised design, having three treatments and seven repeats per treatment, was used for determining chlorophyll a fluorescence in broccoli plants affected by iron toxicity. One month old Legacy hybrid broccoli seedlings (Brassica oleracea var. Italica) were taken as initial vegetal material and sown in a greenhouse in Tunja, Colombia, in glass vessels containing a nutritive solution. Iron sulphate at 100 and 250 ppm Fe concentration was added about three weeks after transplanting (as well as control with out iron sulphate) for inducing reactions to the excess of metal in the plants. Chlorophyll fluorescence was measured in leaves which were fully expanded and adapted to the dark seventeen days after applying Fe. Analysis of variance (ANOVA) revealed significant differences for all the variables evaluated in this study, except for the coefficient of non-photochemical quenching (qN).The results showed that toxicity caused by an excess of iron induced an increased level of stress in the broccoli plants evaluated here, there by affecting photosystem II's (PSII) maximum quantumyield (Fv/Fm), PS II operating efficiency (ΦII), coefficient of photochemical quenching (qP) and electron transport rate. The foregoing makes it evident that an excess of iron modified the fraction of excitation energy destined for photochemical and non-photochemical processes, thereby having a direct impact on photosynthesis in the plants evaluated here.

Keywords : photosystem II (PSII); photosynthetic capacity; light capture; photosynthetic reaction centre; excess energy; photo-inhibition.

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