Silício como atenuador de estresse causado por glifosato em mudas de laranjeira valência
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2022-03-04
Autores
Barbosa, Inácio João
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Universidade Estadual Paulista (Unesp)
Resumo
O glifosato é o herbicida mais utilizado no controle das plantas daninhas nas áreas de produção de citros e pode causar injúrias às plantas de laranjeira em caso da ocorrência da deriva ou das aplicações acidentais, provocando assim, danos na fotossíntese. Embora estudos que relacionam a nutrição de plantas com o manejo de estresse por herbicidas sejam escassos, o silício (Si), um elemento benéfico, pode ser uma alternativa devido sua ação na proteção das espécies vegetais em situação de estresse. Para isso, dois experimentos foram realizados na casa de vegetação com mudas de laranjeira de oito meses de idade, variedade Valência enxertada sobre Swingle. O primeiro experimento teve como objetivo, avaliar o efeito de doses de glifosato (0; 144; 288; 432; 576; 720; 864; 1008; 1.152; 1.296 e 1.440 g e.a.ha-1 ), em blocos casualizados e 4 repetições, sobre as mudas de laranjeira. O segundo experimento teve como objetivo avaliar o efeito do Si como atenuante da toxicidade do glifosato em mudas de laranjeira. Os tratamentos foram constituídos de aplicações de silício via fertirrigação (0 e 2 mmol L-1 complementada com 5 aplicações foliares de 2 mmol L-1 ) e doses do glifosato (0; 576; 1.008 e 1.440 g e.a.ha-1 ), 4 repetições e em delineamento de blocos casualizados. No primeiro experimento avaliou-se, aos 60 dias após a aplicação dos tratamentos, o nível de extravasamento dos eletrólitos, teor de fenóis totais, teor da clorofila total, carotenoides totais, feofitina total, eficiência quântica do fotossistema II, número de folhas e a massa seca de folhas. No segundo experimento, as avaliações foram realizadas em folhas maduras aos 09 e 23 e, em folhas novas, aos 16 e 30 dias após aplicação do glifosato. No primeiro experimentou o glifosato aumentou o nível de extravasamento dos eletrólitos e teor da feofitina total, diminuiu o conteúdo de fenóis totais, número de folhas e a massa seca de folhas. Não afetou a eficiência quântica do fotossistema II, a clorofila total e carotenoides totais. No segundo experimento aplicação do glifosato aumentou o nível de extravasamento dos eletrólitos e de MDA, indicadores de condições estressoras. Também reduziu a clorofila a e b, carotenoides, aumentou a feofitina total. A aplicação do Si foi eficiente em diminuir o nível dos eletrólitos e do conteúdo de MDA; O Si apresentou efeito positivo na mitigação do estresse por glifosato ao aumentar a eficiência quântica do fotossistema II, o conteúdo da clorofila a e b, carotenoides e promoveu maior número e massa seca de folhas. O elemento também aumentou a resposta do sistema antioxidante não enzimático, medida pelos níveis de prolina, fenóis e carotenoides. O Si, assim, diminui o efeito do glifosato em mudas de laranjeira, mesmo em doses mais altas.
- Glyphosate is the most used herbicide for weed control in citrus production areas and can cause damage to orange plants in case of drift or accidental applications, causing damage to photosynthesis. Although there are few studies that relate plant nutrition to the management of stress by herbicides, silicon (Si), a beneficial element, may be an alternative due to its action in the protection of plant species under stress. For this, two experiments were carried out in a greenhouse with eight-monthold orange tree seedlings, Valencia variety grafted on Swingle. The first experiment aimed to evaluate the effect of glyphosate doses (0; 144; 288; 432; 576; 720; 864; 1008; 1,152; 1,296 and 1,440 g e.a.ha-1), in randomized blocks and 4 replications, in orange seedlings. The second experiment aimed to evaluate the effect of Si as an attenuator of glyphosate toxicity in orange seedlings. The treatments consisted of silicon applications via fertigation (0 and 2 mmol L-1 supplemented with 5 foliar applications of 2 mmol L-1) and glyphosate doses (0; 576; 1,008 and 1,440 g e.a.ha1), 4 replications. and in a randomized block design. In the first experiment, 60 days after the application of treatments, the level of electrolyte extravasation, total phenols, total chlorophyll, total carotenoids, total pheophytin, quantum efficiency of photosystem II, number of leaves and dry leaf mass. In the second experiment, evaluations were performed on mature leaves at 9 and 23 days and on young leaves at 16 and 30 days after glyphosate application. In the first experiment, glyphosate increased the level of electrolyte extravasation and the total pheophytin content, decreased the total phenol content, the number of leaves and the dry mass of the leaves. It did not affect the quantum efficiency of photosystem II, total chlorophyll and total carotenoids. In the second experiment, the application of glyphosate increased the level of electrolyte and MDA extravasation, indicators of stressful conditions. It also reduced chlorophyll a and b, carotenoids, increased total pheophytin. The application of Si was efficient in reducing the electrolyte content and MDA content; Si had a positive effect on mitigating the stress caused by glyphosate, increasing the quantum efficiency of photosystem II, the content of chlorophyll a and b, carotenoids and promoting greater number and dry mass of leaves. The element also increased the response of the non-enzymatic antioxidant system, measured by levels of proline, phenols and carotenoids. Thus, Si diminishes the effect of glyphosate on orange seedlings, even at higher doses.
- Glyphosate is the most used herbicide for weed control in citrus production areas and can cause damage to orange plants in case of drift or accidental applications, causing damage to photosynthesis. Although there are few studies that relate plant nutrition to the management of stress by herbicides, silicon (Si), a beneficial element, may be an alternative due to its action in the protection of plant species under stress. For this, two experiments were carried out in a greenhouse with eight-monthold orange tree seedlings, Valencia variety grafted on Swingle. The first experiment aimed to evaluate the effect of glyphosate doses (0; 144; 288; 432; 576; 720; 864; 1008; 1,152; 1,296 and 1,440 g e.a.ha-1), in randomized blocks and 4 replications, in orange seedlings. The second experiment aimed to evaluate the effect of Si as an attenuator of glyphosate toxicity in orange seedlings. The treatments consisted of silicon applications via fertigation (0 and 2 mmol L-1 supplemented with 5 foliar applications of 2 mmol L-1) and glyphosate doses (0; 576; 1,008 and 1,440 g e.a.ha1), 4 replications. and in a randomized block design. In the first experiment, 60 days after the application of treatments, the level of electrolyte extravasation, total phenols, total chlorophyll, total carotenoids, total pheophytin, quantum efficiency of photosystem II, number of leaves and dry leaf mass. In the second experiment, evaluations were performed on mature leaves at 9 and 23 days and on young leaves at 16 and 30 days after glyphosate application. In the first experiment, glyphosate increased the level of electrolyte extravasation and the total pheophytin content, decreased the total phenol content, the number of leaves and the dry mass of the leaves. It did not affect the quantum efficiency of photosystem II, total chlorophyll and total carotenoids. In the second experiment, the application of glyphosate increased the level of electrolyte and MDA extravasation, indicators of stressful conditions. It also reduced chlorophyll a and b, carotenoids, increased total pheophytin. The application of Si was efficient in reducing the electrolyte content and MDA content; Si had a positive effect on mitigating the stress caused by glyphosate, increasing the quantum efficiency of photosystem II, the content of chlorophyll a and b, carotenoids and promoting greater number and dry mass of leaves. The element also increased the response of the non-enzymatic antioxidant system, measured by levels of proline, phenols and carotenoids. Thus, Si diminishes the effect of glyphosate on orange seedlings, even at higher doses.
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Palavras-chave
Fotossíntese, Estresse oxidativo, Herbicidas