Maximum quantum yield of photosystem II to assist in the measurement of herbicide selectivity in popcorn

Abstract

The objective of this study was to evaluate the selectivity/phytotoxicity of herbicides (mesotrione, nicosulfuron, and tembotrione) using the maximum quantum yield of photosystem II associated with biometric analyses. The experiment was conducted using three popcorn genotypes (BRS Angela, IAC-125 and UENF-14) and three herbicides (mesotrione, tembotrione and nicosulfuron, and a control treatment "WITH WEEDING?". The quantum yield of photosystem II was obtained through a modulated light portable fluorometer MINI-PAM, from the chlorophyll a fluorescence. Regarding the biometric analyses, the following characteristics were evaluated: a) number medium of ears of the corn, b) grain yield in kg ha -1 , c) average weight of 100 grains, and d) popping expansion. The genotypes were sensitive to tembotrione with higher intensity for the IAC -125. The maximum quantum yield of photosystem II showed useful tool for studies of selectivity/phytotoxicity symptoms of herbicides used.

Physiological aspects of corn plants related to mesotrione herbicide selectivity

“…However, doses as high as 0.30kg ha -1 , which might be used due to negligence while preparing the solution or lack of information and instructions, affected the photosynthesis pathway. Although the UENF 506-8 cultivar plants recovered its gas exchange and chlorophyll a fluorescence values,, the period in which the plants presented the lowest A values can affect yield as observed in popcorn plants (Freitas et al, 2014).…”

“…Plants exposed to dose of 0.30 kg ha -1 showed a slight trend to decreased values of ET 0 /CS 0 linked to the increases in ABS/RC and RC/CSo values. These changes can result in DI 0 /RC increase as observed in Lathyrus genus and act as a protection mechanism to maintain the F v /F m ratio (Silvestre et al, 2014), which has shown to be sensitive variable and useful for studies of mesotrione in popcorn (Freitas et al, 2014).. However, such changes were not sufficient to maintain F v /F m ratio in corn plants, showing that the reduction in photosynthesis rates was linked mainly to photochemical limitations.…”

“…Therefore, weed control is an economic necessity and the chemical control has been the most common method used on large areas. However, the efficiency varies among herbicides depending on the environmental conditions, time of application and weed species infesting the crop (Freitas et al, 2014).…”

Associações Herbicidas Aplicadas Na Cultura Do Milho Pipoca Em Diferentes Estádios De Desenvolvimento

“…Dentre os principais herbicidas utilizados em pós-emergência na cultura do milho, se destacam os inibidores da síntese de carotenoides (mesotrione e tembotrione), da ALS (nicosulfuron) e do fotossitema II (atrazine) (Freitas et al, 2014). Contudo, para avaliação dos efeitos tóxicos dos herbicidas no milho pipoca geralmente se analisa o efeito de doses dos herbicidas, bem como do estádio de aplicação (Cavalieri et al, 2012).…”

“…ns Não significativo a 5% de probabilidade pelo teste F. * Significativo a 5% de probabilidade pelo teste F diferenças na produtividade em função da aplicação dos herbicidas, sendo todos seletivos para a cultura de milho pipoca (Tabela 3). Apesar disto, é importante ressaltar os resultados da bibliografia que relatam que híbridos de milho pipoca possuem diferentes sensibilidades aos herbicidas nicosulfuron, mesotrione e tembotrione (Freitas et al, 2009(Freitas et al, , 2014Cavalieri et al, 2012). Médias seguidas por letras minúsculas distintas na coluna diferem pelo teste LSD de Fisher (p≤0,05).…”