Morphological and Biochemical Alterations of Paddy Rice in Response to Stress Caused by Herbicides and Total Plant Submersion

Abstract

-Herbicide selectivity in paddy rice varies in several aspects, among which are the environmental conditions. The aim of the study was to evaluate the effect of herbicide application and total plant submersion on morphological and biochemical changes in paddy rice. Total chlorophyll and carotenoids, catalase activity, ascorbate peroxidase and superoxide dismutase, total phenolic content, lipid peroxidation and hydrogen peroxide levels were assessed. Leaf samples were collected 24 hours and 7 days after the application of water regimes. The results observed in the first experiment show that cultivars Puitá INTA CL, IRGA 417 and IRGA 422 CL are more tolerant to total submersion. The most sensitive cultivars are IRGA 424, BRS Querência, EPAGRI 108 and BRS Taim. In general, cultivar Puitá INTA CL had lower oxidative damage than BRS Querência when under submersion. To eliminate excess free radicals, BRS Querência had increased activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) than Puitá INTA CL under submersion. Formulations with imazethapyr + imazapic and imazapyr + imazapic caused greater reduction in the total chlorophyll and carotenoid contents at 7 days after the establisment of water regimes (DAT). Therefore, the data show that exposing cultivars to total submersion and herbicides increased oxidative stress as well as induced changes in the activities of antioxidant enzymes. Keywords:Oxidative stress, hypoxia, Oryza sativa, herbicide selectivity. RESUMO - carotenoides aos sete dias após o estabelecimento dos regimes hídricos (DAT). Portanto, os dados evidenciam que a exposição dos cultivares à submersão e aos herbicidas induzem maior estresse oxidativo, bem como alterações nas atividades das enzimas antioxidantes.Palavras-chave: estresse oxidativo, hipóxia, Oryza sativa, seletividade de herbicida.

Interferência entre plantas daninhas e a cultura: alterações no metabolismo secundário

“…A aplicação de herbicidas altera os níveis de peróxido de hidrogênio. Para cultivares de arroz submetidas à diferentes herbicidas houve o aumento médio de 67% no nível de peróxido de hidrogênio (Marchezan et al, 2017). Já a exposição das plantas daninhas Leptochloa chinensis e Hedyotis verticillata a aplicação de 2,4-DTBP aumentou as atividades das enzimas superóxido dismutase, peroxidase e catalase, o qual indica a indução do mecanismo secundário de defesa (Chuah et al, 2016).…”

Biochemical Alterations of Weeds in Response to Stress Caused by Herbicides and Total Plant Submersion

“…Comparing the water regimes, SOD enzyme activity was lower only in L. peruviana plants when submerged. Marchezan et al (2017), where the rice cultivar BRS Querência presented an increased activity of SOD enzyme, which may be associated to the increase in H 2 O 2 levels, demonstrating that SOD activity probably stimulated the production of reactive oxygen species (ROS). To reduce the damage caused by oxidative stress, plants have a defense system that includes several antioxidant enzymes in different cell compartments.…”

“…Chlorophyll a molecules are the main pigments responsible for the capture of light for the photochemical reactions present in the reaction centers of the photosystems. Thus, the decline of these compounds may affect the photosynthetic activity, thus damaging plants growth (Ramesh et al, 2002;Langaro et al, 2016;Marchezan et al, 2017).…”

Interferência entre plantas daninhas e a cultura: alterações no metabolismo secundário

“…Para cultivares de arroz submetidas à diferentes herbicidas houve o aumento médio de 67% no nível de peróxido de hidrogênio (Marchezan et al, 2017). Já a exposição das plantas daninhas Leptochloa chinensis e Hedyotis verticillata a aplicação de 2,4-DTBP aumentou as atividades das enzimas superóxido dismutase, peroxidase e catalase, o qual indica a indução do mecanismo secundário de defesa (Chuah et al, 2016).…”

“…Alterações no conteúdo de metabólitos das culturas foram detectados quando em competição com plantas daninhas (Langaro et al, 2011;Afifi e Swanton, 2012;Silva et al, 2014;Gal et al, 2015). Alterações nas rotas metabólicas das espécies oriundas de aplicação de herbicidas, modificam o metabolismo secundário das plantas (Chuah et al, 2016;Marchezan et al, 2017). Atualmente os trabalhos que consideram interferência de plantas daninhas, avaliam além das alterações já conhecidas causadas pela interferência, as modificações sobre o metabolismo secundário das espécies.…”