Características fotossintéticas de cultivares de mandioca tratadas com fluazifop-p-butyl e fomesafen.

Abstract

Resumo -Um dos mais importantes componentes do custo de produção da mandioca refere-se aos gastos com o controle de plantas daninhas. Isto pode ser atribuído a pouca disponibilidade de herbicidas registrados para uso nessa cultura. Uma das maneiras para selecionar novos agrotóxicos seletivos para culturas pode ser através da avaliação de características fotossintéticas de plantas após aplicação de herbicidas. Objetivou-se com este trabalho avaliar os efeitos dos herbicidas fluazifop-p-butyl e fomesafen, aplicados isoladamente e em mistura, sobre as variáveis fotossintéticas de cinco cultivares de mandioca (Cacau-UFV, Platina, Coqueiro, Coimbra e IAC-12). Os tratamentos foram aplicados aos 30 dias após o plantio, quando as plantas de mandioca apresentavam aproximadamente 30 cm de altura. Aos 30 dias após a aplicação dos tratamentos foram avaliadas a concentração de CO 2 subestomática, a taxa fotossintética e o CO 2 consumido pela cultura. A mistura dos herbicidas fluazifop-pbutyl+fomesafen provocou incrementos na quantidade de CO 2 consumida, concentração de CO 2 na câmara subestomática e na taxa fotossintética dos cultivares avaliados. No entanto, a aplicação dos herbicidas separadamente não alterou as características avaliadas apresentando potencial para a utilização na fase de pós-emergência da mandioca.Palavras-chave -Característica fisiológica. Consumo de CO 2 . Fotossíntese. Herbicida. Manihot esculenta Crantz. Abstract -The spending on weed control is an important component of production cost of cassava. It may be due to a limited availability of registered herbicides for use on this culture. To select new selective herbicides for cultures, it may be used the evaluation of plant photosynthetic characteristics after application. Thus, with this work, it was aimed to evaluate the effects of fluazifop-p-butyl and fomesafen herbicides, applied separately and in mixture, on the photosynthetic variables of five cassava cultivars (Cacau-UFV, Platina, Coqueiro, Coimbra and IAC-12). The treatments were applied 30 days after planting, when the cassava plants had approximately 30 centimeters of height. 30 days after application of treatments, it was evaluated substomatic CO 2 concentration, photosynthetic rate and CO 2 consumption by culture. The mixture of the herbicides fluazifopp-butyl + fomesafen caused increases in the quantity of CO 2 consumed, CO 2 concentration in the substomatal chambers and photosynthetic rate of the cultivars evaluated. However, the application of herbicides separately did not alter the characteristics evaluated with potential for use in post-emergence of cassava.

Augmenting iron accumulation in cassava by the beneficial soil bacterium Bacillus subtilis (GBO3)

“…The iron is translocated to the shoot through the transpiration flow in the form of complexes with organic acids ( Curie and Briat, 2003 ) and accumulates in chloroplasts ( Terry and Abadia, 1986 ) where most of the chlorophyll is concentrated ( Fernández et al, 2008 ) allowing for optimal photosynthetic performance ( Black and Osmond, 2003 ). Indeed, transpiration is generally negatively correlated with iron deficiency in plants ( Larbi et al, 2006 ) and in cassava specifically positively correlated with plant growth ( Silveira et al, 2012 ). In appears that GB03 exposure also delays leaf senescence which could be a result of higher iron and chlorophyll ( Larbi et al, 2006 ) allowing leaves to remain green longer and/or GB03 suppresion of the hormone abscisic acid in shoots ( Zhang et al, 2008 ), which can also delay senescence ( Alonso et al, 1999 ).…”

“…Leaf physiological parameters on the fifth fully expanded leaf including photosynthesis (A) and transpiration (E) were obtained 140 days after cassava planting using an infrared gas analyzer (IRGA) ACL model PRO l (Analytical Development Co. Ltd, Hoddesdon, UK; Silveira et al, 2012 ). Immediately after collecting non-distructive measurements, plants were harvested for plant height, shoot dry weight and iron content via spectrophotometric and X-ray microanalysis.…”

Application Height in Herbicides Efficiency in Bean Crops

“…Fluazifop-P-butyl acts by inhibiting Acetyl-CoA (Acetyl coenzyme A or acetyl-CoA) carboxylase (ACC) enzyme, preventing lipid synthesis in plants (Silva & Silva, 2007). It controls with high efficiency grass plants originating from seeds (Silveira et al, 2012). Fomesafen causes the inhibition of protoporphyrinogen oxidase enzyme and efficiently controls dicotyledonous weeds early in their development (Silva & Silva, 2007).…”

Physiological responses of Coffea arabica cultivars in association with arbuscular mycorrhizal fungi

“…Thus, where the photosynthetic rate is higher, the CO 2 concentration tends to be lower. The CO 2 consumed is directly related to the photosynthetic intensity of the plant, that is, the higher the photosynthetic rate, the faster the CO 2 is consumed, and the lower its concentration inside the leaf Silveira et al (2012).…”