Óxido nítrico em plantas: breve abordagem sobre essa molécula multifuncional

Diversos estudos vêm sendo realizados com a finalidade de aumentar o conhecimento sobre a ocorrência e a atividade do óxido nítrico (ON) nas plantas. Nesse sentido, a presente revisão objetivou abordar alguns aspectos referentes ao ON nas plantas, tais como propriedades químicas, vias de síntese, efeitos fisiológicos, ação antioxidante, transdução do sinal, interação com hormônios vegetais e expressão gênica. Nos últimos anos, muitos avanços têm sido obtidos em relação à síntese de ON e seus efeitos fisiológicos nas plantas. Porém, os mecanismos moleculares que fundamentam seus efeitos permanecem pouco compreendidos. É sinalizada uma investigação em detalhes sobre as estreitas interações entre ON, Ca2+, ADP-ribose cíclica (cADPR) e proteínas quinases. Além disso, ainda não foi possível identificar uma enzima vegetal que apresente atividade semelhante à da óxido nítrico sintase (NOS). A elucidação de tais aspectos representa um desafio para futuros trabalhos.Several studies were carried out in order to improve the knowledge about the occurrence and activity of nitric oxide (NO) in plants. Thus, this review discusses some aspects related to NO in plants such as chemical properties, synthesis pathways, physiological effects, antioxidant action, signal transduction, interaction with plant hormones and gene expression. In the last years, many advances have been obtained regarding NO synthesis and its physiological effects in plants. However, the molecular mechanisms underlying its effects remain poorly understood. It is signalized that tight interplays among NO, Ca2+, cyclic ADP ribose (cADPR), and protein kinases need to be investigated in details. In addition, it has not yet been possible to identify a plant enzyme displaying a nitric oxide synthase (NOS)-like activity. The elucidation of such aspects represents a challenge to future studies

Nitrogen fertilization of fall panicum cultivars (Panicum dichotomiflorum Michx.): biochemical and agronomical aspects

Information on improved fall panicum cultivars and agronomical pratices is scarce because of the relatively small importance of this crop in Brazil. The present study aimed to evaluate levels of nitrogen sidedressing on plant development and biochemical characteristics of two fall panicum cultivars. The experiment was set up under plastic tunnel conditions in Botucatu, São Paulo, Brazil, with plants growing inside asbestos-cement boxes. The experimental design was a randomized block setup and treatments consisted of six levels of nitrogen fertilization (0, 40, 80, 120, 160, and 200 mg L-1) applied at the onset of tillering on two fall panicum cultivars (AL Mogi and AL Tibagi). The application of increasing levels of nitrogen to fall panicum plants increased chlorophyll content, total amino acids, plant dry matter nitrogen content, plant height, tillering and grain yield, and decreased plant dry matter sugar content. The cultivars had similar performances in relation to the evaluated variables, as a response to nitrogen sidedressing.São escassas as informações sobre cultivares melhoradas e técnicas culturais adequadas à cultura do painço. Este experimento objetivou avaliar o efeito da aplicação de níveis de nitrogênio (N) em cobertura no desenvolvimento e nos atributos bioquímicos de duas cultivares de painço. Para tanto, instalou-se um experimento em Botucatu (SP), em caixas de cimento amianto, mantidas em túnel plástico. O delineamento experimental foi em blocos casualizados, em esquema fatorial 2x6, com dois cultivares de painço (AL Mogi e AL Tibagi) e seis níveis de adubação nitrogenada (0, 40, 80, 120, 160 e 200 mg L-1), aplicada em cobertura, no início do perfilhamento. Os dois cultivares utilizados tiveram comportamento semelhante em relação às variáveis avaliadas, em resposta à aplicação de N em cobertura. A aplicação de doses de N na cultura do painço proporcionou incrementos nos teores relativos de clorofila, aminoácidos totais, nitrogênio total e altura das plantas, e redução dos teores de açúcares na matéria seca, até o intervalo entre 120 e 160 mg de N L-1. O perfilhamento e produção de grãos tiveram aumento linear com a aplicação de N. A adubação nitrogenada não afetou a produção de matéria seca

Atividade de superóxido dismutase em plantas de soja (Glycine max L.) cultivadas sob estresse oxidativo causado por herbicida

Some herbicides frequently used in economical main crops, such as soybean, cause oxidative stress in aerobical organisms, characterized by formation of oxygen reactive species, like superoxide radicals. Superoxide dismutase (SOD) is an enzyme that plays important role in response to oxidative stress in plants, by acting over superoxide radical, forming hydrogen peroxide and molecular oxygen. The aim of this research was to determine the activity of SOD in order to verify your action to protect soybean plants protection against oxidative stress induced by oxyfluorfen, and also the lipoperoxide content formed in the experiment conditions. Oxyfluorfen was applied at 2500, 5000 and 10000 mg/L. Soybean plants were sprayed at different development phases (16, 23 and 30 days after germination). Samples of shoot were collected 24, 48 and 72 hours after application. The experimental design used was completely randomized, in factorial arrangement (4x3), with five replications. It was observed that oxyfluorfen at 2500 and 10000 mg/L increased SOD activity, while lipoperoxide content increased in plants submitted with all concentrations. The results showed that SOD has action against oxidative stress induced by oxyfluorfen in soybean plants.     Alguns herbicidas freqüentemente utilizados em culturas agrícolas de importância econômica, tais como a soja, causam nos organismos aeróbicos estresse oxidativo, caracterizado pela formação de espécies reativas de oxigênio, como os radicais superóxido (O2-). A superóxido dismutase (SOD) é uma enzima que desempenha importante papel na resposta ao estresse oxidativo nas plantas, atuando sobre o radical O2-, formando peróxido de hidrogênio e oxigênio molecular. Este trabalho teve como objetivo determinar a atividade da SOD a fim de verificar sua ação na proteção das plantas de soja contra o estresse oxidativo induzido pelo herbicida oxyfluorfen e também o teor de lipoperóxidos formados nas condições do experimento. As doses aplicadas do herbicida foram de 2500, 5000 e 10000 mg/L, através de pulverização na parte aérea das plantas de soja em diferentes estádios de desenvolvimento (16, 23 e 30 dias após a germinação). Amostras da parte aérea foram coletadas às 24, 48 e 72 horas após a aplicação dos tratamentos e utilizadas para as determinações. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 4x3 (quatro tratamentos e três estádios de desenvolvimento), com cinco repetições. O oxyfluorfen nas doses de 2500 e 10000 mg/L ocasionou aumento da atividade da SOD nos estádios de 16, 23 e 30 dias, enquanto que o teor de lipoperóxidos aumentou nas plantas submetidas à todas as concentrações. Os resultados confirmam que a SOD tem ação contra o estresse oxidativo induzido pelo oxyfluorfen em plantas de soja

Nitric oxide in plants: a brief discussion on this multifunctional molecule

Diversos estudos vêm sendo realizados com a finalidade de aumentar o conhecimento sobre a ocorrência e a atividade do óxido nítrico (ON) nas plantas. Nesse sentido, a presente revisão objetivou abordar alguns aspectos referentes ao on nas plantas, tais como propriedades químicas, vias de síntese, efeitos fisiológicos, ação antioxidante, transdução do sinal, interação com hormônios vegetais e expressão gênica. Nos últimos anos, muitos avanços têm sido obtidos em relação à síntese de on e seus efeitos fisiológicos nas plantas. Porém, os mecanismos moleculares que fundamentam seus efeitos permanecem pouco compreendidos. É sinalizada uma investigação em detalhes sobre as estreitas interações entre ON, Ca2+, ADP-ribose cíclica (cADPR) e proteínas quinases. Além disso, ainda não foi possível identificar uma enzima vegetal que apresente atividade semelhante à da óxido nítrico sintase (NOS). A elucidação de tais aspectos representa um desafio para futuros trabalhos.Several studies were carried out in order to improve the knowledge about the occurrence and activity of nitric oxide (NO) in plants. Thus, this review discusses some aspects related to NO in plants such as chemical properties, synthesis pathways, physiological effects, antioxidant action, signal transduction, interaction with plant hormones and gene expression. In the last years, many advances have been obtained regarding NO synthesis and its physiological effects in plants. However, the molecular mechanisms underlying its effects remain poorly understood. It is signalized that tight interplays among NO, Ca2+, cyclic ADP ribose (cADPR), and protein kinases need to be investigated in details. In addition, it has not yet been possible to identify a plant enzyme displaying a nitric oxide synthase (NOS)-like activity. The elucidation of such aspects represents a challenge to future studies

Nodulação, aspectos bioquímicos, crescimento e produtividade do feijoeiro em função da aplicação de bioestimulante

The use of biostimulants can alter plant growth and development, but the action of they may be varied according to the stage of development of the plant. The aim was to evaluate the effects of forms and times of a biostimulant (cytokinin, indolebutyric acid, and gibberellic acid) application on nodulation, some biochemical aspects, growth and yield of common bean cultivar Perola. The treatments were: Control (without application); TS - 250 mL ha(-1) seed treatment; V-4 - 250 mL ha(-1) foliar spray in V-4 stage; R-5 - 250 mL ha(-1) foliar spray in R-5 stage; TS+V-4 - 250 mL ha(-1) in TS + 250 mL ha(-1) in V-4; TS+R-5 - 250 mL ha(-1) in TS + 250 mL ha(-1) in R-5; V-4+R-5 - 250 mL ha(-1) in V-4 + 250 mL ha(-1) in R-5, and TS+V-4+R-5 - 250 mL ha(-1) in TS + 250 mL ha(-1) in V-4 + 250 mL ha(-1) in R-5. The foliar biostimulant application in the vegetative (V-4) or early reproductive phase (R-5) increases nodulation, root growth, content of soluble sugars, content of total amino acid and nitrate reductase activity, however, does not interfere with shoot growth and grain yield of common bean

Ultraviolet-B and water stress effects on growth, gas exchange and oxidative stress in sunflower plants

The effects and interaction of drought and UV-B radiation were studied in sunflower plants (Helianthus annuus L. var. Catissol-01), growing in a greenhouse under natural photoperiod conditions. The plants received approximately 1.7 W m(-2) (controls) or 8.6 W m(-2) (+UV-B) of UV-B radiation for 7 h per day. The UV-B and water stress treatments started 18 days after sowing. After a period of 12 days of stress, half of the water-stressed plants (including both UV-B irradiated or non-irradiated) were rehydrated. Both drought and UV-B radiation treatments resulted in lower shoot dry matter per plant, but there was no significant interaction between the two treatments. Water stress and UV-B radiation reduced photosynthesis, stomatal conductance and transpiration. However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercelluar CO(2) concentration was initially reduced in all treatments compared to control plants but it increased with time. Photosynthetic pigments were not affected by UV-B radiation. Water stress reduced photosynthetic pigments only under high UV-B radiation. The decrease was more accentuated for chlorophyll a than for chlorophyll b. As a measure for the maximum efficiency of photosystem II in darkness F (v)/F (m) was used, which was not affected by drought stress but initially reduced by UV-B radiation. Independent of water supply, UV-B radiation increased the activity of pirogalol peroxidase and did not increase the level of malondialdehyde. on the other hand, water stress did not alter the activity of pirogalol peroxidase and caused membrane damage as assessed by lipid peroxidation. The application of UV-B radiation together with drought seemed to have a protective effect by lowering the intensity of lipid peroxidation caused by water stress. The content of proline was not affected by UV-B radiation but was increased by water stress under both low and high UV-B radiation. After 24 h of rehydration, most of the parameters analyzed recovered to the same level as the unstressed plants