RESUMO
Glyphosate is a nonselective herbicide of systemic action that inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, thus compromising amino acid production and consequently the growth and development of susceptible plants. The objective of this study was to evaluate the hormetic effect of glyphosate on the morphology, physiology, and biochemistry of coffee plants. Coffee seedlings (Coffea arabica cv Catuaí Vermelho IAC-144) were transplanted into pots filled with a mixture of soil and substrate and subjected to ten doses of glyphosate: 0, 11.25, 22.5, 45, 90, 180, 360, 720, 1440, and 2880 g acid equivalent (ae) ha-1. Evaluations were performed using the morphological, physiological, and biochemical variables. Data analysis for the confirmation of hormesis occurred with the application of mathematical models. The hormetic effect of glyphosate on coffee plant morphology was determined by the variables plant height, number of leaves, leaf area, and leaf, stem, and total dry mass. Doses from 14.5 to 30 g ae ha-1 caused the highest stimulation. In the physiological analyses, the highest stimulation was observed upon CO2 assimilation, transpiration, stomatal conductance, carboxylation efficiency, intrinsic water use efficiency, electron transport rate, and photochemical efficiency of photosystem II at doses ranging from 4.4 to 55 g ae ha-1. The biochemical analyses revealed significant increases in the concentrations of quinic acid, salicylic acid, caffeic acid, and coumaric acid, with maximum stimulation at doses between 3 and 140 g ae ha-1. Thus, the application of low doses of glyphosate has positive effects on the morphology, physiology, and biochemistry of coffee plants.
RESUMO
The "second generation" of glyphosate-tolerant soybean (RR®2 soybean) was developed through a different technique of insertion of the glyphosate-insensitive EPSPs gene. Information on the selectivity of glyphosate, alone or in combination, in RR2 soybean is lacking. This study evaluated the effects of glyphosate, isolated or in associations, applied at post-emergence (V4), at agronomic performance and seed quality of soybean cultivar NS 6700 IPRO (RR2). The experimental design was randomized block with four replications and seven treatments, conducted in the field for two growing seasons. The treatments consisted of glyphosate herbicide, alone or in combination with clethodim, cloransulam, chlorimuron, lactofen and fluazifop, besides the control without application. Analysis was performed for crop injury, Soil and Plant Analyzer Development (SPAD) index, as well as variables related to agronomic performance (height, number of pods per plant, yield and 1,000-seed weight) and seed quality (vigor, germination, abnormal seedlings and dead seeds). An additional test was conducted with the same cultivar and treatments in a greenhouse in a completely randomized design with four replications. The herbicides did not affect agronomic performance and seed quality of RR2 soybean. Thus, the soybean cultivar NS 6700 IPRO (RR2) was tolerant to glyphosate, alone or combined with other herbicides applied in post-emergence (V4).(AU)
A "segunda geração" de soja tolerante ao glifosato (soja RR®2) foi desenvolvida por meio de uma diferente inserção do gene EPSPs insensível ao referido herbicida. Informações sobre a seletividade de glifosato, isolado ou em associação, são faltantes em soja RR2. Este estudo avaliou os efeitos do glifosato, isolado ou em associações, aplicado em pós-emergência (V4), no desempenho agronômico e na qualidade de sementes do cultivar de soja NS 6700 IPRO (RR2). Adotou-se o delineamento experimental de blocos ao acaso com quatro repetições e sete tratamentos, realizados no campo em duas safras. Os tratamentos consistiram no herbicida glifosato, isolado ou em associação com clethodim, cloransulam, chlorimuron, lactofen e fluazifop, além da testemunha sem aplicação. Foi realizada a avaliação dos sintomas de injúria e índice SPAD (Soil and Plant Analyzer Development), bem como de variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade e massa de 1.000 sementes) e à qualidade das sementes (vigor, germinação, plântulas anormais e sementes mortas). Experimento complementar foi realizado com o mesmo cultivar e tratamentos em casa de vegetação em delineamento inteiramente casualizado com quatro repetições. Os herbicidas não afetaram o desempenho agronômico e a qualidade de sementes da soja RR2. Assim, o cultivar NS 6700 IPRO (RR2) foi tolerante ao glifosato, isolado ou em associação com outros herbicidas aplicados em pós-emergência (V4).(AU)