Efeito de herbicidas a base de glifosato sobre as respostas fotossintéticas de macrófitas de ecossistemas lóticos tropicais
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Data
2019-04-17
Autores
Diagonel, Guilherme
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Vários estudos observacionais sobre macrófitas de ecossistemas lóticos têm contribuído com o aumento do conhecimento ecológico destes organismos nestes ambientes. Entretanto, ainda persistem lacunas importantes neste conhecimento, entre as quais estão as relações de causa e efeito que potencialmente existem entre perturbações provocadas pela atividade antrópica e aspectos da fisiologia e da ecologia destes organismos. Com o objetivo de superar, obviamente em parte, esta lacuna, o presente estudo propõe, através de experimentos laboratoriais, avaliar os efeitos de resíduos de herbicidas usados nas lavouras agrícolas, em especial aqueles a base de glifosato (Roundup®) e seu metabólito (AMPA), sobre parâmetros fotossintéticos de espécies de angiospermas aquáticas típicas de ecossistemas lóticos tropicais. As avaliações das taxas fotossintéticas e de respiração no escuro foram realizadas através da evolução do oxigênio dissolvido, aplicando-se a técnica das garrafas claras e escuras e da fluorescência de clorofila a, que foi avaliada com o fluorômetro subaquático Diving-PAM. Os valores dos parâmetros fotossintéticos medidos/calculados para cada tratamento avaliado foram submetidos à estatística descritiva e as eventuais diferenças entre eles foram avaliadas através da análise de variância utilizando o teste de Scott-Knott e o t-Student. Foram observados alguns poucos efeitos fitotóxicos associados às espécies de macrófitas estudadas, porém, quase nenhuma diferença estatisticamente significativa foi efetivamente encontrada, tanto positivas quanto negativas, entre os tratamentos e o grupo controle. A despeito deste padrão global, as espécies responderam de modo espécie-específico à exposição ao Roundup® e ao AMPA, sendo que Egeria densa foi aquela que registrou maior susceptibilidade para a perda de eficiência fotossintética sob influência destas substâncias, enquanto que Myriophyllum aquaticum tendeu a aumentar a sua produtividade fotossintética, especialmente em presença de AMPA. Do ponto de vista ecológico, este resultado merece atenção, já que estas espécies de macrófita estão entre as mais bem distribuídas em ambientes aquáticos tropicais e subtropicais do Brasil.
Even with many observational studies regarding lotic ecosystems, macrophytes that have contributed with great knowledge about the ecology of these organisms in these environments. However, there are still important gaps in this knowledge, among which are the cause and effect relationships that potentially exist between disturbances caused by anthropic activity and aspects of the physiology and ecology of these organisms. With the objective of overcoming, in part, this gap, the present study proposes, through laboratory experiments, to evaluate the effects of herbicide residues used in agricultural crops, especially those based on glyphosate (Roundup®) and your metabolite (AMPA) on photosynthetic parameters of aquatic angiosperm species typical of tropical lotic ecosystems. The evaluation of photosynthetic rates and respiration in the dark were performed through the evolution of dissolved oxygen, applying the light and dark bottle technique and chlorophyll a fluorescence, which was evaluated with the Diving-PAM underwater fluorometer. The values of the photosynthetic parameters measured / calculated for each evaluated treatment were submitted to descriptive statistics and any differences between them were evaluated through analysis of variance using the Scott-Knott and t-Student test. In spite of this global pattern, species responded specificially to exposure to Roundup® and AMPA, and Egeria densa was the one that registered the greatest susceptibility to the loss of photosynthetic efficiency under the influence of these substances, whereas Myriophyllum aquaticum tended to increase their photosynthetic productivity, especially in the presence of AMPA. From an ecological point of view, this result deserves attention, as these macrophyte species are among the best distributed in tropical and subtropical aquatic environments in Brazil.
Even with many observational studies regarding lotic ecosystems, macrophytes that have contributed with great knowledge about the ecology of these organisms in these environments. However, there are still important gaps in this knowledge, among which are the cause and effect relationships that potentially exist between disturbances caused by anthropic activity and aspects of the physiology and ecology of these organisms. With the objective of overcoming, in part, this gap, the present study proposes, through laboratory experiments, to evaluate the effects of herbicide residues used in agricultural crops, especially those based on glyphosate (Roundup®) and your metabolite (AMPA) on photosynthetic parameters of aquatic angiosperm species typical of tropical lotic ecosystems. The evaluation of photosynthetic rates and respiration in the dark were performed through the evolution of dissolved oxygen, applying the light and dark bottle technique and chlorophyll a fluorescence, which was evaluated with the Diving-PAM underwater fluorometer. The values of the photosynthetic parameters measured / calculated for each evaluated treatment were submitted to descriptive statistics and any differences between them were evaluated through analysis of variance using the Scott-Knott and t-Student test. In spite of this global pattern, species responded specificially to exposure to Roundup® and AMPA, and Egeria densa was the one that registered the greatest susceptibility to the loss of photosynthetic efficiency under the influence of these substances, whereas Myriophyllum aquaticum tended to increase their photosynthetic productivity, especially in the presence of AMPA. From an ecological point of view, this result deserves attention, as these macrophyte species are among the best distributed in tropical and subtropical aquatic environments in Brazil.
Descrição
Palavras-chave
Macrófitas, Fotossíntese, Herbicidas, Glifosato