Crescimento de Mentha piperita L, cultivada em solução nutritiva com diferentes doses de potássio

The research aimed at the evaluation of the influence of different potassium doses on the growth and development of Mentha piperita L. The experiment was conducted with stalks rooted in a commercial substrate and transplanted to a complete nutritive solution varying the treatments as following: (a) 234 mg L-1 of K; (b) 117 mg L-1 of K; and (c) 58.5 mg L-1 of K. Plants were evaluated at 21, 42, 63, 84 and 105 days after transplanting (DAT). In this study there were determined the physiological indexes leaf area ratio (LAR), specific leaf area (SLA), net assimilatory rate (NAR) and relative growth rate (RGR) were determined. The results indicated that the decreasing of K concentration to 25% did not affect the LAR, SLA, NAR and RGR physiological indexes

Morphological and physiological alterations induced by lactofen in soybean leaves are reduced with nitric oxide

O lactofen é um herbicida difeniléter recomendado para controlar plantas daninhas de folhas largas em campos de soja (Glycine max) e seu mecanismo de ação é a inibição da protoporfirinogênio-IX oxidase (Protox), que atua na biossíntese de clorofilas. Essa inibição resulta em um acúmulo de protoporfirina-IX, o que leva à produção de espécies reativas de oxigênio (ROS), causando estresse oxidativo. Conseqüentemente, podem ocorrer manchas, enrugamento e queima das folhas, o que leva à paralisação temporária do crescimento da cultura. Porém, o óxido nítrico (NO) atua como um antioxidante na eliminação direta das ROS. Assim, o objetivo deste trabalho foi verificar, por meio de avaliações fitométricas e bioquímicas, o efeito protetor do NO em plantas de soja tratadas com o herbicida lactofen. Plantas de soja foram pré-tratadas com diferentes doses de Nitroprussiato de Sódio (SNP), substância doadora de NO, e então pulverizadas com 168 g a.i. ha-1 lactofen. O pré-tratamento com SNP foi benéfico, pois o NO reduziu os sintomas de injúria causados pelo lactofen nos folíolos jovens e manteve baixos teores de açúcares solúveis. Porém, o NO proporcionou crescimento mais lento das plantas. Desta forma, posteriores estudos são necessários para elucidar os mecanismos de ação do NO na sinalização do estresse promovido pelo lactofen na cultura da soja.Lactofen is a diphenylether herbicide recommended to control broad-leaved weeds in soybean (Glycine max) fields and its mechanism of action is the inhibition of protoporphyrinogen-IX oxidase (Protox), which acts in the chlorophyll biosynthesis. This inhibition results in an accumulation of protoporphyrin-IX, which leads to the production of reactive oxygen species (ROS) that cause oxidative stress. Consequently, spots, wrinkling and leaf burn may occur, resulting in a transitory crop growth interruption. However, nitric oxide (NO) acts as an antioxidant in direct ROS scavenging. Thus, the aim of this work was to verify, through phytometric and biochemical evaluations, the protective effect of NO in soybean plants treated with the herbicide lactofen. Soybean plants were pre-treated with different levels of sodium nitroprusside (SNP), a NO-donor substance, and then sprayed with 168 g a.i. ha-1 lactofen. Pre-treatment with SNP was beneficial because NO decreased the injury symptoms caused by lactofen in young leaflets and kept low the soluble sugar levels. Nevertheless, NO caused slower plant growth, which indicates that further studies are needed in order to elucidate the action mechanisms of NO in signaling the stress caused by lactofen in soybean crop

Análise de crescimento de plantas de manjericão tratadas com reguladores vegetais Growth analysis of basil plants submitted to plant growth regulators

O estudo objetivou avaliar o efeito de reguladores vegetais no desenvolvimento de plantas de manjericão (Ocimum basilicum L.). Para tanto, plantas foram cultivadas em vasos de 12 litros em casa de vegetação. O delineamento foi em blocos casualizados com quatro tratamentos contendo quatro repetições e cinco coletas. Os tratamentos consistiram de aplicações foliares dos seguintes reguladores vegetais: ácido giberélico (GA3) 100 mg L-1, ácido 2-cloroetilfosfônico (ethephon) 100 mg L-1 e cinetina 100 mg L-1, que foram preparados em solução aquosa. As aplicações dos reguladores vegetais foram realizadas aos 40, 60 e 80 dias após a semeadura (DAS), e o desenvolvimento das plantas avaliado em coletas a intervalos de 14 dias, aos 50, 64, 78, 92 e 106 DAS. Em plantas tratadas com cinetina, observaram-se os maiores valores para os índices fisiológicos, com maior desenvolvimento, devido ao aumento da área foliar e à massa seca promovido por esse regulador vegetal.<br>The objective of this study was to evaluate the effect of plant growth regulators on the development of basil plants (Ocimum basilicum L.). The experiment was seeded in 12-liter pots and carried out in a greenhouse. The experimental design was a randomized block with four treatments, four replications, and five harvest times. Treatments consisted of the following plant growth regulators applied as foliar sprays: gibberellic acid (GA3), 2-chloroethyl phosphonic acid (ethephon), and kinetin at 100 mg L-1, which were prepared in aqueous solution. Plant growth regulator applications were performed at 40, 60, and 80 days after planting (DAP) and plant development was evaluated during harvest time, at 14-day intervals, 50, 64, 78, and 106 DAP. Plants treated with kinetin showed the highest physiological index values, and exhibited greater development due to increases in leaf area and dry matter provided by this plant growth regulator

Optimization of supercritical carbon dioxide extraction of bioactive flavonoid compounds from spearmint (Mentha spicata L.) leaves by using response surface methodology

The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using supercritical carbon dioxide (SC-CO2) extraction. Extraction was carried out according to face-centred central composite design, and independent variables were pressure (100, 200 and 300 bar), temperature (40, 50 and 60 °C) and co-solvent amount (3, 6 and 9 g/min). The extraction process was optimized by using response surface methodology for the highest crude extraction yield of bioactive flavonoid compounds. The optimal conditions were identified as 209.39 bar pressure, 50.00 °C temperature and 7.39 g/min co-solvent amount. The obtained extract under optimum SC-CO2 condition was analysed by high-performance liquid chromatography. Seven bioactive flavonoids including catechin, epicatechin, rutin, luteolin, myricetin, apigenin and naringenin were identified as major compounds. The results of quantification showed that spearmint leaves are potential source of antioxidant compounds

Produção de biomassa, teor e composição do óleo essencial de Mentha x piperita L. em resposta a fontes e doses de nitrogênio Biomass production, essential oil yield and composition of Mentha x piperita L. according to nitrogen sources and doses

A adubação nitrogenada influencia o teor e a qualidade dos óleos essenciais de plantas aromáticas. O objetivo deste trabalho foi avaliar a influência de diferentes fontes e doses de nitrogênio na produção de biomassa e teor do óleo essencial de M. x piperita. O delineamento experimental foi de blocos casualizados em esquema fatorial 2 x 3 (duas fontes de nitrogênio e três doses). A aplicação nitrogenada de cobertura foi realizada 30 dias após o transplante das mudas. O óleo essencial foi extraído pelo processo de hidrodestilação em aparelho graduado Clevenger e sua composição química foi analisada por cromatografia gasosa acoplada à espectrometria de massa. As fontes e doses de nitrogênio não influenciaram significativamente a biomassa de folhas e ramos, assim como a produtividade e o teor do óleo essencial. No entanto, a fonte de nitrogênio pode alterar significativamente a composição do óleo essencial de M. x piperita. O teor de mentol e neomentol foi menor quando 40 kg ha-1 de uréia foi aplicada, em comparação com a mesma dose de sulfato de amônio. Os teores de mentona foram influenciados apenas pela fonte de nitrogênio, onde níveis mais elevados foram observados quando o sulfato de amônio foi aplicado. Nenhuma alteração nos teores de mentofurano foi encontrada para as diferentes fontes e doses de nitrogênio. Considerando a grande importância econômica de mentol presente no óleo essencial de menta, os resultados obtidos indicaram que a utilização de 20 kg ha-1 de nitrogênio é suficiente para garantir a boa produtividade de óleo essencial e alto teor de mentol, e que altas doses de uréia devem ser evitadas.<br>Nitrogen fertilization affects the essential oil yield and composition of aromatic plants. The objective of this work was to evaluate the effect of nitrogen sources and doses on biomass production and essential oil yield and composition of M. x piperita L. The experimental design was in randomized blocks with four replications and the treatments in a 2 x 3 factorial design, corresponding to two nitrogen sources and three nitrogen doses. The nitrogen topdressing was applied 30 days after planting. The essential oil was obtained by hydrodestilation using a Clevenger apparatus, and the composition was analyzed by gas chromatography and coupled to a mass spectrometry. The nitrogen sources and doses did not significantly affect the leaf and stem biomass, as well as the essential oil yield and productivity. However, the nitrogen source can significantly change the essential oil composition of M. x piperita. The level of menthol and neomenthol was lower when 40 kg ha-1 of urea was applied compared to the same dose of ammonium sulphate. Menthone levels were affected only by the nitrogen source, where higher levels were observed when ammonium sulphate was applied. No changes on menthofurane levels were found for different nitrogen sources and doses. Considering the great economic importance of menthol from mint essential oils, the obtained results indicated that the use of 20 kg ha-1 of nitrogen is enough to guarantee satisfactory essential oil yield and great menthol levels and that high doses of urea should be avoided