RESUMO
The differential growth and yield response of plant species to rising carbon dioxide concentrations and climatic change may alter species diversity within biomes. The Pampa Biome in South America is an important grassland biome of agronomic and environmental importance. Acanthostyles buniifolius (Chirca) is one of the most important weeds in natural pasture areas widely distributed in southern South America and can adversely affect livestock production. The current study was designed to identify possible responses of Chirca to CO2 concentration ([CO2]) and drought that would indicate higher adaptation and potential proliferation within the Pampa Biome. Chirca plants were cultivated at two CO2 concentrations (400 (a[CO2]) and 700 (e[CO2]) µmol mol-1) and two water conditions (under water restriction-15% of the pot capacity; and plants without water restriction-pot capacity). Besides growth parameters, we also determined water potential (ѱw), relative water contents (RWC), proline, glycine betaine, total soluble sugars, hydrogen peroxide, lipid peroxidation, superoxide dismutase (SOD), ascorbate peroxidase (APX) activity, chlorophyll A and B, carotenoids and root dry mass (RDM). Plants exposed to e[CO2] are more efficient in water use and have a greater increase in root dry mass, enabling greater adaptation to climate-induced droughts. Among the biochemical changes observed in the plants under drought stress, the accumulation of proline, glycine betaine, and total soluble sugars were the most evident mechanisms allowing plants to tolerate drought stress by osmotic adjustment.
RESUMO
ABSTRACT: This study aimed to evaluate the antagonistic effect of the mixture ofacetyl coenzyme-A carboxylase (ACCase) enzyme inhibiting herbicides and auxin herbicides in Lolium multiflorum and to determine mechanisms to mitigate this possible effect. The first experiments were conducted by associating the herbicide clethodim (108 g a.i. ha−1), quizalofop-p-ethyl (54 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (108+54 g a.i. ha−1) with 2,4-D (1005 g a.e. ha−1) or triclopyr (720 g a.e. ha−1), in addition to the sole application of the respective graminicides. Another experiment included clethodim (54; 81; 108; 162; 216 g a.i. ha−1), quizalofop-p-ethyl (27; 40.5; 54; 81; 108 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (54+27; 81+40.5; 108+54; 162+81; 216+108 g a.i. ha−1) mixed with 2,4-D (1005 g a.e. ha−1), or triclopyr (720 g a.e. ha−1), in addition to the control treatments without herbicide application. In the second experiment, herbicides clethodim (108 g a.i. ha−1), quizalofop-p-ethyl (54 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (108+54 g a.i. ha−1) in combination with the herbicides 2,4-D (1005 g a.e. ha−1) or triclopyr (720 g a.e. ha−1)had malathion (1000 g a.i. ha−1) or glyphosate (720 g a.e. ha−1) mixed, in addition to the sole applications of the graminicides. The herbicide clethodim + quizalofop-p-ethyl did not present an antagonistic interaction with the auxin herbicides, and obtained 85% weed control. To obtain control similar to the sole application of this graminicide, the dose of the herbicide clethodim needs to be increased by 20%. However, the mixture of the herbicide quizalofop-p-ethyl with 2,4-D and triclopyr affects the ryegrass control. The use of strategies that increase the absorption of ACCase herbicides or the inhibition of P450 enzymes are ways to mitigate the antagonistic effect caused by the association of the two auxin herbicides.
RESUMO: O objetivo do trabalho foi avaliar o efeito antagônico da mistura de herbicidas inibidores da enzima ACCase e herbicidas auxínicos em Lolium multiflorum e determinar mecanismos de mitigação deste possível efeito. No primeiro momento foram conduzidos experimentos associando o herbicida clethodim (108 g i.a. ha-1), quizalofop-p-ethyl (54 g i.a. ha-1) e clethodim + quizalofop-p-ethyl (108 + 54 g i.a. ha-1) com 2,4-D (1005 g e.a. ha-1) ou triclopyr (720 g e.a. ha-1), além da aplicação isolada dos respectivos graminicidas. Outro experimento contou com clethodim (54; 81; 108; 162; 216 g i.a ha-1), quizalofop-p-ethyl (27; 40,50; 54; 81; 108 g i.a ha-1) e clethodim + quizalofop-p-ethyl (54 + 27; 81 + 40,50; 108 +54; 162 +81; 216 + 108 g i.a ha-1) em mistura com 2,4-D (1005 g e.a ha-1) ou triclopyr (720 g e.a. ha-1), além das testemunhas sem aplicação herbicida. No segundo momento os herbicidas clethodim (108 g i.a. ha-1), quizalofop-p-ethyl (54 g i.a. ha-1) e clethodim + quizalofop-p-ethyl (108 + 54 g i.a. ha-1) em associação com os herbicidas 2,4-D (1005 g e.a ha-1) ou triclopyr (720 g e.a. ha-1), contaram com adição de malathion (1000 g i.a. ha-1) ou glyphosate (720 g e.a. ha-1), além das aplicações isoladas dos graminicidas. O herbicida clethodim + quizalofop-p-ethyl não apresentou interação antagônica com os herbicidas auxínicos, obtendo controle de 85%. Já para o herbicida clethodim é necessário o aumento de dose em 20 % é capaz de obter controle similar a aplicação isolada deste graminicida. Porém para o herbicida quizalofop-p-ethyl a mistura com os herbicidas 2,4-D e triclopyr repercute na diminuição do controle do azevém. O uso de estratégias que aumente a absorção do herbicida inibidor de ACCase ou a inibição das enzimas P450 são formas de mitigar o efeito antagônico causado pela associação destes dois tipos de herbicidas.
RESUMO
Given the importance of soybean to the global economy and as a food source, improving crop management techniques is integral to obtaining higher yields. As such, this study aimed to assess the yield of soybean cultivars as a function of different glyphosate salt formulations, doses and application times. Two field experiments were conducted simultaneously using a randomized block design and 3x4x2 factorial scheme, with three repetitions. Factor A consisted of three glyphosate formulations: isopropylamine salt (Roundup Original®), ammonium salt (Roundup WG®), and potassium salt (Zapp Qi®), factor B four application times: 0, 14, 28, 42 days after planting (DAP), and factor C two doses: the recommended dose of 720 grams of acid equivalent per hectare and twice that (1440 grams of acid equivalent per hectare). There was no difference between the glyphosate salts for the BMX Ativa RR® cultivar, but yields of BMX Apolo RR® submitted to ammonium salt were 28% higher than those recorded for the other salts studied. Glyphosate potassium salt resulted in lower soybean yields. Potassium salt application between 14 and 28 DAP caused greater toxicity in both the soybean cultivars analyzed.
Diante da importância da cultura da soja tanto na economia mundial quanto para a alimentação, a melhoria das técnicas de cultivo torna-se um ponto fundamental na obtenção de maiores produtividades. Desta forma o objetivo do trabalho foi avaliar a produtividade de cultivares de soja sob a influência da aplicação de diferentes sais de glyphosate, doses e épocas de aplicação. Dois experimentos de campo foram realizados simultaneamente em delineamento de blocos casualizados com arranjo trifatorial (3x4x2) com três repetições. O fator A consistiu de três formulações de glyphosate: sal de isopropilamina (Roundup Original®), sal de amônio (Roundup WG®), sal de potássio (Zapp Qi®). O fator B consistiu de quatro épocas de aplicação: 0, 14, 28, 42 dias após a semeadura (DAS). O fator C consistiu em duas doses: a dose recomendada de 720 gramas de equivalente ácido por hectare e duas vezes a dose recomendada com 1440 gramas de equivalente ácido por hectare. Para a cultivar BMX Ativa RR® não se observou diferença quanto aos sais, porém a cultivar BMX Apolo RR® submetida a aplicação de sal de amônio demostrou uma produtividade 28% superior em relação aos demais sais. O glyphosate na formulação sal de potássio apresentou redução da produtividade da cultura da soja. Aplicações de glyphosate na formulação sal de potássio realizadas entre os 14 e 28 dias após a semeadura causam maior toxidez em ambas cultivares de soja utilizadas.
