Glyphosate applied at low doses increased the dry weight of sugarcane and eucalyptus plants in all experiments. This hormetic effect was related to low dose effects on CO assimilation rate, stomatal conductance and transpiration rate, indicating that low glyphosate doses enhance photosynthesis of plants. © 2017 Society of Chemical Industry.

-Chlorophyll fluorescence is currently used as a rapid diagnostic and nondestructive method to detect and quantify damage on the photosynthetic apparatus of leaves on weeds, crops and ornamental/coniferous trees in response to both environmental stress and herbicides. This study aimed to evaluate chlorophyll fluorescence in guanandi plants (Calophyllum brasiliense) after application of different postemergence herbicides. The experiment was performed in a completely randomized design, with six treatments (control, bentazon, sulfentrazone, isoxaflutole, atrazine and glyphosate) and five replications. The herbicide treatments were applied with a stationary sprayer, and electron transport rate (ETR) was subsequently analyzed with OS5p Multi-Mode Chlorophyll Fluorometer. In the monitored period, guanandi plants subjected to atrazine showed higher sensitivity to chlorophyll fluorescence than the other treatments. Although bentazon is a photosystem II inhibitor, it showed no major changes in electron transport for the studied species and in the monitored period. In summary, ETR is a good parameter to evaluate the effect of some herbicides on Calophyllum brasiliense plants.Keywords: electron transport rate, bentazon, sulfentrazone, isoxaflutole, atrazine, glyphosate. RESUMO -A fluorescência da clorofila tem sido utilizada como um método diagnóstico rápido e não destrutivo para detectar e quantificar danos no aparato fotossintético das folhas em plantas daninhas

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Glyphosate is the most widely used herbicide in the world. In sugarcane, it is used as a herbicide when applied at its field rate, but it is also used as ripener when applied as low doses. However, the effects of glyphosate on plant metabolism and sugarcane growth are not fully understood. This study aimed to evaluate the metabolic changes and the effects on sugarcane plant growth caused by the application of different doses of glyphosate. Sugarcane plants were grown in a greenhouse and subjected to glyphosate applications at doses of 7.2; 18; 36; 72; 180; 360 and 720 g a.e. ha −1. Plants grown without an herbicide application were used as a control. Plants from each treatment were collected at 2, 7, 14, and 21 days after treatment (DAT) application to quantify the levels of shikimic acid, quinic acid, shikimate-3-phosphate, glyphosate, α-amino-3-hydroxy-5-methyl-4isoxazolepropionic acid (AMPA), phenylalanine, tyrosine, and tryptophan. Visual evaluations of plant intoxication were performed at the same time as the collection of plants, and the quantification of their shoot dry biomass was performed at 21 DAT. At doses of glyphosate greater than 72 g a.e. ha −1 , increases in the levels of shikimic acid, quinic acid, and shikimate-3-phosphate occurred and AMPA was detected in the plants. Initially, glyphosate caused increases in the plant levels of phenylalanine and tyrosine at doses of 72 and 180 g a.e. ha −1 , although a decrease in the levels of aromatic amino acids subsequently occurred at and above the doses of 72 or 180 g a.e. ha −1. The doses ranging from 7.2 to 36 g a.e. ha −1 promoted an increase in plant shoot biomass, and doses greater than 72 g a.e. ha −1 caused significant reductions in dry mass.

O herbicida indaziflam apresenta atividade residual no solo e pode se tornar problema para os cultivos agrícolas, pela possibilidade de carryover em culturas sucessoras. Assim, objetivou-se selecionar potenciais espécies bioindicadoras para presença de resíduos do indaziflam no solo. Foram realizados dois experimentos em casa de vegetação, utilizando vasos de polietileno de 0,00025 m3, ambos distribuídos no delineamento em blocos ao acaso com quatro repetições. No primeiro experimento foram utilizadas onze espécies com potencial uso como bioindicadoras: arroz, aveia, beterraba, capim-braquiária, feijão, girassol, milho, pepino, soja, tomate e trigo submetidas à aplicação de sete doses de indaziflam (0; 6,25; 12,5; 25; 50; 75 e 100 g i.a. ha-1). em pré-emergência das culturas. No segundo experimento, cinco sub-doses (0; 0,3906; 0,7812; 1,5625 e 3,125 g i.a. ha-1) do indaziflam foram aplicadas nas espécies que não emergiram na menor dose ou concentração do herbicida no primeiro experimento. Foram avaliadas a fitointoxicação e altura de plantas (ALT) aos 3, 7, 14 e 21 dias após a emergência (DAE). Aos 21 DAE avaliou-se matéria seca de parte aérea (MSPA), de raiz (MSR) e total (MST). O aumento das doses de indaziflam provocou aumento dos sintomas de fitointoxicação e reduções nas variáveis ALT, MSPA, MSR e MST. Entre as espécies avaliadas, em monocotiledôneas na ordem: capim-braquiária, arroz, milho, trigo, aveia e em eudicotiledôneas: tomate, pepino, girassol, feijão, soja apresentam potencial para uso como bioindicadora em estudos com indaziflam. A beterraba apresentou ser extremamente sensível ao herbicida não emergindo em nenhuma das doses estudadas.