Utilization of the chlorophyll a fluorescence technique as a tool for selecting tolerant species to environments of high irradiance

we examine the hypothesis that the chlorophyll a fluorescence technique can be an efficient tool to support the selection of species adapted to high irradiance and therefore, suitable for use in initial rehabilitation projects of degraded areas. the experiment was conducted at the pedro de moura operational base, amazonas, brazil. the fluorescence transients were obtained using a portable fluorometer for leaves of bombacopsis macrocalyx (bm), eugenia cumini (ec), iryanthera macrophyla (im) and senna reticulata (sr), which were subjected to high irradiance between 12:00 am and 1:00 p.m. using the ojip test, the following were calculated: performance index (piabs), density of reaction centres per cross section (rc/cs), maximum efficiency of photosystem ii (fpo), and probability of energy excitation (yo) or that an absorbed photon (feo) moves an electron beyond quinone a. the highest value of piabs was found in ec (0.40) while the lowest values were found in bm (0.08) and im (0.06). these low values of piabs in bm and im were a result of the low values for rc/cs (121 for bm; 142 for im) and fpo (0.50 for bm; 0.48 for im) when compared to the values in ec (rc/cs=303; fpo=0.72) and sr (rc/cs=326; fpo=0.73). it was also observed that in sr the decrease in piabs when compared with ec resulted from a low value of yo, which was 32 % lower than the value found in ec. regarding the piabs per plant, ec had the largest number of individuals with high performance while im and bm had the largest numbers of individuals with low performance. in conclusion, the chlorophyll a fluorescence technique enabled the evaluation of the photochemical performance of plants in the field, in turn permitting the selection of species most suitable for rehabilitation of degraded areas.