Influence of Drought on Graminicide Phytotoxicity in Wild Oat (Avena fatua) Grown under Different Temperature and Humidity Conditions

Abstract

Controlled environmental experiments were carried out to determine the phytotoxicity of several graminicides on wild oat (Avena futua L.) as influenced by combination of drought and temperature stress or drought and low relative humidity. Compared with unstressed conditions (20/15°C plus adequate soil moisture), imazamethabenz phytotoxicity to wild oat was reduced significantly when plants were exposed to a combination of drought and high temperature (30/20°C) stress. Imazamethabenz phytotoxicity was reduced almost as much by high temperature stress alone as by a combined temperature and drought stress. When herbicides were applied to wild oat plants subjected to drought alone or to drought plus high temperature, the observed reduction in phytotoxicity from greatest to least was: fenoxaprop ‫ס‬ diclofop > flamprop > imazamethabenz. Fenoxaprop performance was most inhibited by the combination of drought plus high temperature, although drought alone and to a lesser degree, high temperature alone, inhibited fenoxaprop action. High temperature had an adverse effect on the efficacy of fenoxaprop at lower application rates. Raising fenoxaprop application rates to 400 g ha −1 overcame the inhibition caused by high temperature alone but only partially alleviated the effect of drought combined with high temperature. When plants were grown under a low temperature regimen the imposition of drought stress had little effect on imazamethabenz phytotoxicity but did reduce fenoxaprop phytotoxicity. At 25/15°C drought reduced the phytotoxicity of fenoxaprop and diclofop greatly but had no significant impact on the performance of any of the herbicides examined, regardless of soil moisture regimen.

The seasonal effects of water stress on Ammopiptanthus mongolicus in a desert environment

“…Proline is an important osmoticum in higher plants. The benefit of the accumulation of proline has been proposed as a compatiable osmotic solute (Handa et al, 1986), as a protein-stabilizing or solubilizing factor under limited cell water conditions (Blackman, 1992) and as a source of reduced nitrogen and carbon (Xie et al, 1997). Previous work (Peter & Masumin, 1994) indicated that organic acid and amine compounds, except proline, were minor contributors to osmotic adjustment.…”

Fatores ambientais que afetam a eficácia de herbicidas inibidores da ACCase: revisão

“…A hipótese de que temperatura do ar elevada favorece a eficácia de herbicidas inibidores da ACCase no controle de plantas daninhas tem limites (Xie et al, 1997;Hatterman-Valenti et al, 2006;Andrews et al, 2007;Cieslik, 2012). Em espécies vegetais de clima frio, como Avena spp., o efeito da temperatura do ar sobre a atividade de clodinafop foi quadrático.…”

“…Na mesma espécie vegetal, a toxicidade de fenoxaprop e diclofop às plantas foi reduzida quando em temperatura do ar elevada (30/ 20 o C dia/noite). O efeito adverso da alta temperatura do ar no controle das plantas de aveia com fenoxaprop foi compensado, em parte, pela elevação da dose do produto (Xie et al, 1997). A menor atividade desse herbicida pode ser atribuída à reduzida retenção de calda (Xie et al, 1995), ao aumento na desintoxicação do produto (Xie et al, 1996) e, possivelmente, à intensa evaporação das gotas aspergidas sob elevada temperatura do ar.…”

“…Contudo, a hipótese de melhor eficácia do herbicida com maior umidade relativa do ar nem sempre é válida (Xie et al, 1997). Com efeito, a permanência de plantas tratadas com fenoxaprop, diclofop e flamprop por seis horas depois da aplicação sob baixa (30%) e alta (95%) umidade relativa do ar não alterou o controle de A. fatua (Xie et al, 1997).…”

“…Com efeito, a permanência de plantas tratadas com fenoxaprop, diclofop e flamprop por seis horas depois da aplicação sob baixa (30%) e alta (95%) umidade relativa do ar não alterou o controle de A. fatua (Xie et al, 1997). Esse trabalho não esclarece os motivos da ausência de resposta dos graminicidas sobre a planta daninha nas diversas condições de umidade relativa do ar estudadas.…”