Soybean is one of the most economically important crops and has experienced adverse physiological and biochemical effects when subjected to drought stress and heat, resulting in lost productivity. Thus, the objective of this work was to evaluate the physiological, metabolic and growth responses of well-watered and drought-treated soybean cultivars under high temperature. The experimental design was set up in randomized blocks, in a factorial scheme with three soybean cultivars (7739 M, Anta 82 and Desafio) and two water levels (100% and 40% field capacity). The experiment was conducted in a controlled growth chamber with a gradual rise in temperature at 41°C for 5 hours daily. Morpho-physiological and metabolic analyses were performed 12 days after the treatments imposition. The parameters of water and osmotic potentials, relative water content, photosynthetic rate, stomatal conductance, transpiratory rate, electron flux for the carboxylation and oxygenation of RuBisCO were decreased for all cultivars under water deficit and high temperature. The results showed that the photorespiration and the rate of electrolyte leakage were increased as well. These results showed that these physiological behaviors are standard for soybean plants under water deficit, regardless of cultivars. The cultivars 7739 M and Desafio showed lower performance than the cultivar Anta 82 for the parameters of total electron flow and effective quantum yield of PS II. The 7739 M and Anta 82 were the only cultivars to show increased nonphotochemical quenching dissipation and total soluble sugar content, respectively, under stress conditions. Desafio cultivar demonstrated greater physiological and growth traits stability, which could potentially indicate double tolerance to these stresses.

In Brazil, the expansion of agricultural activity and the associated indiscriminate use of herbicides such as glyphosate is directly related to the loss of biodiversity in the Cerrado. The identification of plant species as bioindicators of herbicide action, especially species native to the area, can help in monitoring the impacts of xenobiotics in the remaining Cerrado. Thus, this study was designed to evaluate the possible use of the native Cerrado species Pouteria torta as a bioindicator of glyphosate action via changes in physiological performance. At 16 months after sowing, the effect of glyphosate was evaluated by applying the following doses: 0 (control), 25, 50, 100, 200, 400, 800, and 1200 g a.e. ha -1 . In response to glyphosate, P. torta exhibited reductions in photosynthesis and chloroplastid pigment content, as well as accumulation of shikimic acid and the occurrence of chlorosis and necrosis. These changes demonstrate the high sensitivity of P. torta to glyphosate and its potential for use as a bioindicator of this herbicide.Keywords: phytotoxicity, photosynthetic processes, biomarker, guapeva, herbicide. Pouteria torta: espécie native do Cerrado Brasileiro como bioindicadora da ação do glyphosate ResumoNo Brasil, a expansão da atividade agrícola, aliada a utilização indiscriminada de herbicidas como o glyphosate, possui relação direta com a perda da biodiversidade no Cerrado. A identificação de espécies vegetais bioindicadoras da ação de herbicidas, particularmente as nativas do Cerrado, pode auxiliar em processos de monitoramento dos impactos desse xenobiótico nas remanescentes do Cerrado. Assim, este estudo foi projetado para avaliar o possível uso de Pouteria torta, espécie nativa do cerrado, como bioindicadora da ação do glyphosate via mudanças na sua performance fisiológica. Após 16 meses de semeadura, o efeito do glyphosate foi avaliado quando aplicadas as seguintes doses: 0 (controle), 25, 50, 100, 200, 400, 800 e 1200 g e. a. ha -1 . Em reposta ao glyphosate, as plantas de P. torta apresentaram redução na sua performance do processo fotossintético e no conteúdo de pigmentos cloroplastídicos, além do acúmulo de ácido chiquímico e da ocorrência de cloroses e necroses. Essas alterações demonstram a alta sensibilidade de P. torta ao glyphosate, o que potencializa a sua utilização como bioindicadora da ação desse herbicida.

12.50; 25, and 75 g a.i.•ha −1 . The growth regulator trinexapac-ethyl did not change the photosynthetic metabolism of plants. However, glyphosate caused damage to the photosynthetic apparatus and a reduction in the carbohydrate concentration and chloroplastid pigments, with casual damage to cell membranes; these effect were more intense at increased doses. The effects of glyphosate were evidenced by the increased concentration of shikimic acid, derived from its mechanism of action. Concludes that, the photosynthetic metabolism of sunflower plants is not affected by the growth regulator trinexapac-ethyl, unlike to the evident effects after application of glyphosate.

Drought is the most harmful environmental factor crop productivity. Some chemicals are used in agriculture to mitigate the damage from this stress on plants. Therefore, we examined whether the spraying of zinc sulfate (ZS), potassium phosphite (KPhi) and the hydrogen sulfide (H2S) donor sodium hydrosulfide (NaHS) would mitigate the deleterious effects of water deficit on sunflower plants by analyzing physiological and biometric characteristics. The experiment was carried out in a greenhouse using a randomized block design with five replications. The treatments were arranged in a 4 x 2 factorial scheme: [Factor A (Alleviators)] - spraying of KPhi (0.5 L ha-1), ZS (3.2 kg ha-1), NaHS (1.2 g ha-1), and water; [Factor B (substrate humidity, SH)] - 100% (well irrigated) and 30% (water deficit, WD) of field capacity. Under WD conditions, alleviators led to the maintenance of higher values of water potential (ΨW), a lower content of leaf malonaldehyde (MDA), and increased activity of the antioxidant enzyme peroxidase (POX), except for ZS. However, leaf osmotic potential, proline concentration, variables related to gas exchange and chlorophyll a fluorescence, and biometric characteristics differed only according to the SH factor. The results of ΨW and MDA for sunflower plants under WD are indicative of the mitigating capacity of ZS, KPhi, and H2S. Thus, the spraying of these compounds on sunflower plants mitigates the effects of WD, acting specifically in physiological processes related to antioxidant responses and in the maintenance of water in leaf tissues.

Modificações fisiológicas em folhas de pequi (CaryocarResumo -O uso de herbicidas é essencial para o controle de plantas daninhas e aumento da produtividade das culturas, porém esses produtos podem afetar a fisiologia e o crescimento de organismos não alvos, incluindo plantas nativas. Nesta pesquisa, objetivou-se avaliar em casa de vegetação climatizada as trocas gasosas, a fluorescência da clorofila a e o teor de pigmentos cloroplastídicos em plantas de pequi (Caryocar brasiliense) tratadas com glyphosate. Os tratamentos, arranjados em blocos casualizados, corresponderam as doses de 0 (controle), 50, 100, 250, 500, 1.000 e 1.500 g ha -1 do equivalente ácido de glyphosate, aplicadas aos 120 dias após o transplantio das mudas de pequi. As avaliações de trocas gasosas e de fluorescência da clorofila a foram realizadas as 24, 48 e 240 horas após a aplicação (HAA) do herbicida e a de pigmentos cloroplastídicos as 240 HAA. Houve reduções nas taxas fotossintética e transpiratória, na condutância estomática, no rendimento quântico efetivo do fotossistema II, no rendimento quântico potencial do fotossistema II e na taxa aparente de transporte de elétrons, exceto para a relação entre a concentração interna e externa de CO2 e do coeficiente de extinção não fotoquímica, que houve acréscimo em função do aumento das doses de glyphosate. Similarmente, as 240 HAA para as variáveis clorofilas a, b, carotenoides e relação clorofila a/b foram observadas reduções lineares nos valores destas variáveis. O glyphosate promove alterações nas variáveis fotossintéticas com reduções nas características de trocas gasosas, na eficiência fotoquímica e no teor de pigmentos cloroplastídicos, principalmente quanto expostas as maiores doses do herbicida. Palavras-chaves: fluorescência da clorofila a; herbicida; pigmentos cloroplastídicos; trocas gasosas Abstract -The use of herbicides is essential for the control of weeds and increase crop productivity, but these products can affect the physiology and growth of non-target organisms, including native plants. The objective of this research was to evaluate in the heated greenhouse the gas exchange, fluorescence of chlorophyll a and chloroplastid pigment content of pequi plants (Caryocar brasiliense) submitted to simulated drift of glyphosate. The treatments were arranged 1 Recebido para publicação em