Resumo em Inglês:

Jasmonates are a class of plant hormones that mediate various aspects in gene and metabolic regulation, defense, stress responses, reproduction and, possibly, communication. Oxidative stress stimulates synthesis of antioxidant metabolites and enhances antioxidant enzyme activities that could protect plant tissues. The aim of this study was to verify the effects of methyl jasmonate (JAME) treatment on the reactive oxygen species (ROS) and on the activities of H2O2 scavenging enzymes, such as superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX EC; 1.11.1.1), and guaiacol peroxidase (GPX; EC 1.11.1.7) in Ricinus communis leaves. The activity of CAT and GPX was transient while SOD activity decreased and APX increased after treatment with JAME. In addition, JAME exposure induced ROS accumulation.

Resumo em Inglês:

The present work was undertaken to study the effects of 24-epibrassinolide (0, 10-10, 10-8 and 10-6 M) on growth (shoot length and number of leaves), protein content and activities of antioxidative enzymes [guaiacol peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), glutathione reductase (EC 1.6.4.2), ascorbate peroxidase (EC 1.11.1.11), superoxide dismutase (EC 1.15.1.1), monodehydroascorbate reductase (EC 1.1.5.4) and dehydroascorbate reductase (EC 1.8.5.1)] in leaves of 60 days-old Brassica juncea L. plants treated with different concentrations of Cr metal. It was observed that treatment of different concentrations (0, 0.5, 1.0, 1.5 and 2.0 mM) of Cr metal alone decreased the shoot length and number of leaves and regulated the enzyme activities and protein concentration of plants. However, seed-presoaking treatments of 24-epibrassinolide improved the growth and stimulated the activities of antioxidant enzymes and protein content in leaves of B. juncea plants thus indicating the stress-ameliorative properties of 24-epibrassinolide.

Resumo em Inglês:

Sweet potato (Ipomoea batatas L.) plants were cultivated in vitro in Murashige and Skoog (MS) medium with 20 and 40 g L-1 of sucrose under two different photon flux densities (21 and 60 µmol m-2 s-1). Leaves developed in vitro mostly showed high variable to maximum fluorescence ratio (F V/F M) , indicating good development of photosynthetic apparatus. This ratio decreased during leaf aging, especially in the plants cultivated in vitro on medium with higher sucrose concentration and higher photon flux. Leaves developed ex vitro showed high F V/F M ratio during whole experiment. The effective photochemical efficiency (F V'/F M') was maximum at 15th day after emergence of leaves. Photosynthetic potential rate was higher in leaves developed in vitro than in leaves originated ex vitro.

Resumo em Inglês:

It is now well-known that plants can uptake not only inorganic nitrogen but also organic nitrogen compounds, mainly amino acids. However, soil proteins are the main pool of amino acids. According to our earlier papers, plants can get access to this source of nitrogen using root-secreted proteases, but the level of proteolytic activity of such root-secreted proteases is species-specific. Our aim was to compare the use of protein as nitrogen source by two vegetable crops having high (Allium porrum) or low (Lactuca sativa) level of activity of root-secreted proteases. Seedlings were cultivated on Murashige and Skoog medium (MS), MS medium without inorganic nitrogen, MS medium without inorganic nitrogen, but with casein in concentration of 0.01%, 0.1% or 1%. Fresh weight of shoot of A. porrum was the highest for seedlings growing on culture medium with casein, but shoots of L. sativa obtained the highest weight growing on the culture medium with inorganic nitrogen. Allium porrum seedlings obtained 15-fold higher proteolytic activity in the culture medium than L. sativa. Seedlings of A. porrum using such high activity of proteases secreted by roots could provide a substantial pool of amino acids for intensive growth. The current studies conducted on A. porrum and L. sativa suggest that the efficiency of protein use in nitrogen nutrition by plants is species-specific.

Resumo em Português:

A variação espacial e temporal das concentrações de nutrientes das folhas e do sedimento entre as raízes de Laguncularia racemosa (L.) Gaertn. f. e Rhizophora mangle L. foi analisada no manguezal do estuário do Rio São Mateus, Espírito Santo, Brasil. No tecido foliar, os nutrientes seguiram a ordem: N > Ca > K > Mg > S > P > Fe > Mn > Zn > Cu, havendo diferença significativa entre espécies e sítios de estudo. Em geral, os teores de K foram mais elevados no período seco em relação ao período chuvoso, para ambas as espécies analisadas, enquanto que Ca e Cu exibiram maiores concentrações no período chuvoso, para Laguncularia racemosa. No sedimento, os nutrientes seguiram a ordem: Mg > Ca > Fe > K > Mn > P > Zn > Cu, em geral, com menores concentrações no sítio onde o sedimento foi mais arenoso. Registrou-se variação significativa das concentrações de nutrientes do sedimento entre os períodos analisados, mas o padrão sazonal não foi claro para todos nutrientes. Concentrações de nutrientes determinadas nas folhas de ambas as espécies não se correlacionaram com as concentrações dos respectivos sedimentos. O fator de concentração foi menor que 1,0 para Fe e entre 1,0 e 3,7 para Mn, Zn e Cu. Estes resultados fornecem evidências fisiológicas sobre a relevância destas espécies arbóreas para o papel dos manguezais como barreira biogeoquímica ao trânsito de metais pesados.

Resumo em Inglês:

Spatial and temporal variation of the nutrient concentrations in leaves and sediment between the roots of Laguncularia racemosa (L.) Gaertn. f and Rhizophora mangle L. was analyzed in the mangrove forest of the estuary of São Mateus River, Espírito Santo, Brazil. In leaves, the nutrients followed the sequence: N> Ca> K> Mg> S> P> Fe> Mn> Zn> Cu, and there were significant differences between species and sites studied. In general, the levels of K were higher in the dry season compared to the rainy season for both species analyzed while Ca and Cu showed higher concentrations in the rainy season for Laguncularia racemosa. In the sediment, the nutrients followed the sequence: Mg> Ca> Fe> K> Mn> P> Zn> Cu, in general, with lower concentrations at the site where the sediment was sandier. We observed a significant variation of nutrient concentrations in the sediment between the periods analyzed, but the seasonal pattern was not clear for all nutrients. Nutrient concentration profile found in leaves of both plant species was not correlated with concentrations found in the respective sediments. The concentration factor was less than 1.0 for Fe and between 1.0 and 3.7 for Mn, Zn and Cu. These results provide physiological evidences about the relevance of these tree species for the role of mangroves as biogeochemical barriers to the transit of heavy metals.

Resumo em Português:

Parâmetros fisiológicos de cultivares de cana-de-açúcar submetidas ao déficit hídrico. Para investigar o processo envolvido na susceptibilidade de plantas de cana-de-açúcar ao déficit hídrico, diferentes parâmetros fisiológicos foram avaliados em cultivares tolerantes (SP83-2847 e CTC15) e sensível (SP86-155) ao déficit hídrico. O déficit hídrico afetou o aparato fotossintético de todas as plantas de forma diferenciada dentro e entre as cultivares. A taxa fotossintética e condutância estomática diminuíram significativamente para todas as cultivares submetidas ao déficit hídrico. Nas plantas controle das cultivares tolerantes (SP83-2847 e CTC15) a taxa fotossintética foi maior do que a cultivar sensível (SP86-155). A cultivar CTC15 apresentou O teor relativo de água mostrou que a cultivar CTC15 apresentou o maior teor relativo de água durante o período de déficit hídrico. A eficiência fotossintética da cultivar SP83-2847 foi mais estável nos últimos dias do tratamento experimental, sugerindo que o decréscimo do teor relativo de água estimulou o ajustamento da capacidade fotossintética para tolerar as mudanças da disponibilidade hídrica. De modo geral, as cultivares tolerantes SP83-2847 e CTC15, apresentaram melhor desempenho fotossintético do que a cultivar sensível SP86-155. Os dados permitem sugerir que tais parâmetros fisiológicos podem ser usados na avaliação e distinção de genótipos de cana-de-açúcar tolerantes e sensíveis ao déficit hídrico.

Resumo em Inglês:

To investigate the processes involved in the susceptibility of sugarcane plants to water deficit, several physiological parameters were evaluated in drought tolerant (SP83-2847 and CTC15) and sensitive (SP86-155) cultivars. The water deficit affected the photosynthetic apparatus of all the plants in different ways, within and among cultivars. The photosynthetic rate and stomatal conductance decreased significantly in all cultivars submitted to water deficit. In control plants of the tolerant cultivars (SP83-2847 and CTC15) the photosynthetic rate was higher than in the sensitive cultivar (SP86-155). Cultivar CTC15 showed the highest relative water content during the dry period. The quantum efficiency photosystem II of cultivar SP83-2847 was more stable in the last days of the experimental treatment, suggesting that the decline in relative water content stimulated an adjustment of photosynthetic capacity to tolerate the changes in water availability. As a whole, the tolerant SP83-2847 and CTC15 cultivars exhibited a better photosynthetic performance than the sensitive SP86-155 cultivar. The data suggest that these physiological parameters can be used in the evaluation and distinction of drought tolerant and sensitive sugarcane genotypes.

Resumo em Inglês:

Rice is a tropical plant, so cold temperature may be detrimental to its development, depending on the genotype and environmental conditions. Degree of lipid unsaturation has been related to cold tolerance due to its effect on membrane stability. So, the aim of this study was to characterize the fatty acid composition and its alterations due to cold temperature in rice genotypes of diversified origin. Forty-four rice genotypes at the V4 stage were submitted to two temperature conditions: 10°C and 28°C for two days and after this they had their leaves collected for lipid extraction and quantification. Control plants were allowed to regrow until presenting four leaves fully expanded and then were subjected to 10°C for ten days for cold tolerance evaluation. Plant survival was measured seven days after recovery at 28°C and the genotypes were grouped in three cold tolerance classes: tolerant, intermediate and sensitive. These classes differed for total saturated and unsaturated fatty acids only under the cold temperature treatment. Further analysis of the more abundant fatty acids: linoleic, linolenic and palmitic, showed that the two last ones differed between tolerant and sensitive genotypes. Linolenic acid increased after cold exposure in cold tolerant genotypes while palmitic acid decreased, and an opposite behavior was found in the cold sensitive genotypes. These evidences indicate that these fatty acids are potential molecular markers useful for breeding programs as well as for future basic studies on cold tolerance in rice.

Resumo em Português:

Adaptabilidade e características anatômicas de folhas em mudas de dendezeiros produzidas pelo resgate de embriões e sementes pré-germinadas. Alterações na estrutura da folha de plantas crescidas em diferentes ambientes têm sido relatadas, como o aumento no tamanho e densidade dos estômatos e a redução no controle estomático, na quantidade de cera epicuticular e na espessura do mesofilo, com alta diversidade de espaços intercelulares. Entretanto, tais alterações são altamente variáveis em função das características fisiológicas e morfológicas próprias de cada espécie. O objetivo deste trabalho foi analisar a adaptabilidade e plasticidade anatômica foliar de mudas de dendezeiros produzidas pelo resgate de embriões e sementes pré-germinadas cultivadas num sistema in vitro ou em casa de vegetação. Cortes transversais e paradérmicos, além da dissociação de tecidos, foram preparados para obtenção dos dados morfométricos e anatômicos. Verificou-se que as condições ambientais do cultivo in vitro influenciaram negativamente os valores da densidade estomática, espessura da epiderme e hipoderme, e os valores obtidos para as células de expansão e do mesofilo foliar. Anatomicamente as folhas de dendezeiro apresentam a mesma composição tecidual em ambas condições de cultivo, com epiderme unisseriada, estômatos do tipo tetracítico de ocorrência em ambas as faces epidérmicas. As células epidérmicas das folhas de plantas in vitro são mais delgadas que as da casa de vegetação. Nas plantas de casa de vegetação a nervura principal é mais desenvolvida sendo formada por apenas um grande feixe vascular, enquanto que plantas cultivadas in vitro desenvolveram de três a quatro feixes vasculares.

Resumo em Inglês:

Changes in the leaf structure of plants grown in different conditions have been reported, such as increase in size and density of stomata and reduction in stomatal control, amount of epicuticular wax, and mesophyll thickness, with a high diversity of intercellular spaces. However, these changes are highly variable depending on the physiological and morphological characteristics of each species. The objective of this work was to analyze the adaptability and anatomical plasticity of oil palm seedlings produced after embryo rescue and pre-germinated seeds. Expanded leaves were prepared for evaluation of morphometric data and anatomical structures. It was verified that the environmental conditions in vitro negatively influenced the stomata density, epidermal and hypodermal thickness, and the values for the expansion cells and leaf mesophile. Anatomically, the oil palm leaves present the same tissues composition in both growth conditions, with uniseriate epidermal cells, and tetracitic stomata occurring in both epidermal surfaces. Epidermal cells from in vitro plants are thinner than ones from greenhouse. The midrib of leaves from greenhouse plants are more developed and is composed by only one central vascular bundle, while plants from in vitro cultivation developed three to four collateral vascular bundles.