Morphophysiological responses and programmed cell death induced by cadmium in <Emphasis Type="Italic">Genipa americana</Emphasis> L. (Rubiaceae) |
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Authors: | Vânia L Souza Alex-Alan F de Almeida Stella G C Lima Júlio C de M Cascardo Delmira da C Silva Pedro A O Mangabeira Fábio P Gomes |
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Institution: | 1.Laboratório de Gen?mica e Express?o Gênica,DCB/UESC,Ilheus,Brazil;2.Laboratório de Fisiologia Vegetal,DCB/UESC,Ilheus,Brazil;3.Laboratório de Anatomia Vegetal,DCB/UESC,Ilheus,Brazil;4.Laboratório de Microscopia Eletr?nica,DCB/UESC,Ilheus,Brazil |
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Abstract: | Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers
may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings.
Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes
which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism
of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in
this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l−1, in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root
tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the
lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular
spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration,
while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and
promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted
morphophysiological changes and caused cell death in roots and leaves tissues of G. americana. |
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