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BACKGROUND: Titanium dioxide nanoparticles (TiO2 NPs) have been reported to have contrasting effects on plant physiology, while their effects on sugar, protein, and amino acid metabolism are poorly understood. In this work, we evaluated the effects of TiO2 NPs on physiological and agronomical traits of tomato (Solanum lycopersicum L.) seedlings. Tomato seeds were treated with TiO2 NPs (1000 and 2000 mg L- 1), TiO2 microparticles (µPs, 2000 mg L- 1) as the size control, and ultrapure water as negative control. RESULTS: The dry matter of stems (DMs), leaves (DMl) and total dry matter (DMt) decreased as particle concentration increased. This trend was also observed in the maximum quantum yield of light-adapted photosystem II (PSII) (Fv´/Fm´), the effective quantum yield of PSII (ΦPSII), and net photosynthesis (Pn). The concentrations of sugars, total soluble proteins, and total free amino acids were unaffected, but there were differences in the daily dynamics of these compounds among the treatments. CONCLUSION: Our results suggest that treating tomato seeds with TiO2 might affect PSII performance, net photosynthesis and decrease biomass production, associated with a concentration- and size-related effect of TiO2 particles.

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OBJECTIVES: Tree legume species play an important role in forest restoration in the tropics. Understanding how different species adjust carbohydrate allocation and growth under distinct nutrient availability will enhance the success of restoring degraded areas. DATA DESCRIPTION: A 2-year tropical forest plantation of the Forest Restoration Program of the Balbina Hydropower Dam was evaluated. Three non-N-fixing (Cenostigma tocantinum, Dipteryx odorata and Senna reticulata) and three N-fixing (Clitoria fairchildiana, Inga edulis and Acacia spp.) tree legume species were either fertilized or not fertilized. Growth rates and biomass allocation were calculated, and carbon (C) fractions and nitrogen (N), phosphorus (P) and nonstructural carbohydrate (NSC) concentrations were determined. Multiple nutrient additions increased the growth rates and aboveground biomass production of fertilized plants. According to the results presented, different species and N- fixers respond differently to fertilization regimes. The authors encourage the use of the presented data in meta-analysis studies that consider the fertilization or nutrient deficiency effects on growth, carbohydrate and nutrient responses. N-fixing species with high biomass growth and foliar N are important for restoring N and C cycles in nutrient-limited soils. Fertilization treatments are fundamental during the early stages of forest plantation development.

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The physiology and biochemistry of young Opuntia spp. cladodes relate with their Crassulacean acid metabolism, which extends over the day-night cycle in four phases, is species-dependent and is affected by water availability. This study aimed to assess the interaction among species, time-of-day, and the soil water potential (ΨW) on biochemical and physiological characteristics of cladodes of Opuntia species. Three-week-old cladodes were harvested at 7:00 a.m. and 3:00 p.m. from plants with or without irrigation for 30 d (-0.17 and -5.72 MPa soil ΨW), from O. albicarpa, O. ficus-indica, O. hyptiacantha, O. megacantha, and O. streptacantha. The experimental design was a factorial 5 x 2 x 2 (species, sampling time and soil ΨW). The experimental unit was one cladode per plant, and six repetitions were evaluated. Total acids, glucose, fructose, sucrose, starch, total phenolics, free amino acids, and soluble proteins concentrations were evaluated, as well as acid invertase and neutral invertase activities. The interaction among species x soil ΨW and species x time of the day was significant (P ≤ 0.05) in all variables evaluated. An exception was the species x soil ΨW on starch concentration (P = 0.1827). The biochemical and physiological characteristics of Opuntia cladodes were modified by the time of the day and soil ΨW interaction, but most of the characteristics were positively or inversely affected depending on the species, frequently displaying a descending trend following O. streptacantha, O. hyptiacantha, O. megacantha, O. albicarpa and O. ficus-indica. The total acids, glucose, fructose, starch, soluble proteins, and free amino acids concentrations revealed that domestication significantly modifies C and N metabolism in Opuntia.

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Herbivory is one of the major biotic stress factors that affect the establishment of plants. However, the main factors that drive herbivory in seedlings of Amazonian tree species are still not well understood. Here we investigated whether contrasting levels of irradiance influence herbivory according to different herbivory indicators and which leaf traits are most related to interspecific variation in herbivory under contrasting irradiance conditions. We measured the leaf area lost as a result of insect herbivory in five tree species planted in a silvicultural system of secondary forest enrichment according to two indicators, herbivore damage (accumulated since plant germination) and herbivory rate (measured over time), and two irradiance conditions, understorey PPFD 2.6 mol·m-2 ·day-1 ) and gap PPFD 33.1 mol·m-2 ·day-1 . Furthermore, we related the interspecific variation in herbivory to a set of leaf traits: SLA, RWC, sclerophylly, phenolic compound content, tannins, condensed tannins and non-structural carbohydrates. Herbivore damage was significantly affected by light availability and species, with the highest percentage variation observed in the Meliaceae (Carapa guianensis and Swietenia macrophylla). For the herbivory rate, only the interspecific variation was significant, with Bertholletia excelsa having the lowest rates. Chemical characteristics (phenolic compounds and tannins) were most related to herbivory rates, as well as highly influenced by light conditions. Non-structural carbohydrates (starch and sucrose) were also related to the interspecific variation in herbivory. The phenolic compounds and starch, as affected by light quantity, are species dependent. Thus, the selective pressure on herbivores may be driven by species-dependent responses to light conditions.

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Non-structural carbohydrates (NSC) are crucial for forest resilience, but little is known regarding the role of bark in NSC storage. However, bark's abundance in woody stems and its large living fraction make it potentially key for NSC storage. We quantified total NSC, soluble sugar (SS) and starch concentrations in the most living region of bark (inner bark, IB), and sapwood of twigs, trunks and roots of 45 woody species from three contrasting tropical climates spanning global extremes of bark diversity and wide phylogenetic diversity. NSC concentrations were similar (total NSC, starch) or higher (SS) in IB than wood, with concentrations co-varying strongly. NSC concentrations varied widely across organs and species within communities and were not significantly affected by climate, leaf habit or the presence of photosynthetic bark. Starch concentration tended to increase with density, but only in wood. IB contributed substantially to NSC storage, accounting for 17-36% of total NSC, 23-47% of SS and 15-33% of starch pools. Further examination of the drivers of variation in IB NSC concentration, and taking into account the substantial contribution of IB to NSC pools, will be crucial to understand the role of storage in plant environmental adaptation.

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Rice is one species that present dormancy after harvest and can be prolonged during seed storage. This work aimed to determine whether gibberellic acid (GA3) is an efficient promoter of dormancy-breaking in rice seeds and evaluate changes in biological structures via histochemistry. The cultivar used was SCS122 Miura submitted to 0 mg L-1, 500 mg L-1, and 1000 mg L-1 of GA3. Germination, viability, root, shoot and seedling length, starch optical microscopy, and quantification of total soluble sugars were performed. The use of 500 mg L-1 and 1000 mgL-1 of GA3 was efficient in dormancy-breaking rice seeds, reducing the percentage of dormant seeds to 4% and 1%, respectively. Despite lowering the dormancy percentage, the presence of GA3 causes an increase in the percentage of abnormal seedlings. Therefore, it cannot be recommended as a method of dormancy-breaking rice seeds at the concentrations used. Optical microscopy is efficient to verify that with the dormancy-breaking, the degradation of starch granules occurs, increasing the availability of totalsoluble sugars for the growth and development of seedlings.

O arroz é uma das espécies que apresenta dormência após a colheita, podendo esta ser prolongada durante o armazenamento das sementes. Este trabalho teve por objetivo determinar se o ácido giberélico (GA3) é um promotor eficiente da superação de dormência em sementes de arroz e avaliar mudanças nas estruturas biológicas via histoquímica.A cultivar utilizada foi aSCS122 Miura submetida a 0 mg L-1, 500 mg L-1e 1000 mg L-1de GA3. Foram realizadas análises de germinação, viabilidade, comprimento de raiz, parte aérea e plântula, microscopia óptica do amido e quantificação dos açúcares solúveis totais. A utilização de 500 mg L-1 e 1000 mg L-1de GA3foi eficiente para a superação da dormência de sementes de arroz, reduzindo o percentual de sementes dormentes para 4% e 1% respectivamente. Apesar de reduzir o percentual dormência, a presença de GA3provoca aumento do percentual de plântulas anormais, e por isso, nas concentrações utilizadas, não pode ser recomendado como método de superação em sementes de arroz. A microscopia óptica é eficiente para verificar que com a superação de dormência, ocorre a degradação dos grânulos de amido, aumentando a disponibilidade de açúcares solúveis totais para o crescimento e desenvolvimento de plântulas.

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Rice is one species that present dormancy after harvest and can be prolonged during seed storage. This work aimed to determine whether gibberellic acid (GA3) is an efficient promoter of dormancy-breaking in rice seeds and evaluate changes in biological structures via histochemistry. The cultivar used was SCS122 Miura submitted to 0 mg L-1, 500 mg L-1, and 1000 mg L-1 of GA3. Germination, viability, root, shoot and seedling length, starch optical microscopy, and quantification of total soluble sugars were performed. The use of 500 mg L-1 and 1000 mgL-1 of GA3 was efficient in dormancy-breaking rice seeds, reducing the percentage of dormant seeds to 4% and 1%, respectively. Despite lowering the dormancy percentage, the presence of GA3 causes an increase in the percentage of abnormal seedlings. Therefore, it cannot be recommended as a method of dormancy-breaking rice seeds at the concentrations used. Optical microscopy is efficient to verify that with the dormancy-breaking, the degradation of starch granules occurs, increasing the availability of totalsoluble sugars for the growth and development of seedlings.(AU)

O arroz é uma das espécies que apresenta dormência após a colheita, podendo esta ser prolongada durante o armazenamento das sementes. Este trabalho teve por objetivo determinar se o ácido giberélico (GA3) é um promotor eficiente da superação de dormência em sementes de arroz e avaliar mudanças nas estruturas biológicas via histoquímica.A cultivar utilizada foi aSCS122 Miura submetida a 0 mg L-1, 500 mg L-1e 1000 mg L-1de GA3. Foram realizadas análises de germinação, viabilidade, comprimento de raiz, parte aérea e plântula, microscopia óptica do amido e quantificação dos açúcares solúveis totais. A utilização de 500 mg L-1 e 1000 mg L-1de GA3foi eficiente para a superação da dormência de sementes de arroz, reduzindo o percentual de sementes dormentes para 4% e 1% respectivamente. Apesar de reduzir o percentual dormência, a presença de GA3provoca aumento do percentual de plântulas anormais, e por isso, nas concentrações utilizadas, não pode ser recomendado como método de superação em sementes de arroz. A microscopia óptica é eficiente para verificar que com a superação de dormência, ocorre a degradação dos grânulos de amido, aumentando a disponibilidade de açúcares solúveis totais para o crescimento e desenvolvimento de plântulas.(AU)

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BACKGROUND: Sugarcane is a tropical crop that can accumulate high concentration of sucrose in the stem as a storage carbohydrate. For that reason, sugarcane accounts for approximately 75% of all the sugar produced in the world and has become the main sugar source to produce first-generation bioethanol in Brazil. Daily rhythms cause plants to adapt and coordinate their metabolism to achieve maximum photosynthesis and carbohydrate production throughout the day. Circadian rhythms arise from the interaction of an internal oscillator and external stimuli, whereas diel rhythms occur in response to a light-dark cycle. Diel signalling contributes to synchronizing circadian rhythms to photoperiods, and levels of carbohydrates oscillate in a diel fashion. Under regular photoperiods, they are synthesized during the daytime and consumed throughout the night as an energy reserve. However, short days can induce higher rates of synthesis during daytime and lower rates of consumption in the dark. Cell wall carbohydrates are also diurnally regulated, and it has been shown that celluloses, hemicelluloses and pectin are deposited/degraded at different times of the day. To assess the diel carbohydrate profile in young sugarcane plants, we measured soluble sugars and cell wall components along a time course in plants subjected either to a regular day or short day. RESULTS: Short-day influenced sucrose synthesis and cell wall components. In short-day a 44% increase in sucrose concentration was detected in the dark, but was stable during the day. Cellulose, hemicellulose and pectin also fluctuate within a 24 h interval when subjected to a short day. A 38% increase in leaf sheath cellulose was observed from the middle of the day to the first hour of the night. Leaf sheath pectin and hemicellulose also increased from the day to the night, while it decreased in leaves. CONCLUSIONS: The presented data show diurnal patterns of soluble sugar metabolism together with temporal regulation of cell wall metabolism for a short day, suggesting that diel signalling has a role in how sugarcane manages sugar accumulation and partitioning. Understanding cell wall synthesis/degradation dynamics may help to improve the yield of sugarcane.

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Leaf gas exchanges, carbohydrate metabolism and growth of three Brazilian Cerrado invasive African grasses were evaluated after growing for 75 days under doubled CO2 concentration and temperature elevated by 3 °C. Results showed that although the species presented photosynthetic C4 metabolism, they all had some kind of positive response to increased CO2. Urochloa brizantha and Megathyrsus maximus showed increased height for all induced environmental conditions. Urochloa decumbens showed only improvement in water use efficiency (WUE), while U. brizantha showed increased CO2 assimilation and M. maximus presented higher biomass accumulation under doubled CO2 concentration. The most significant improvement of increased CO2 in all three species appears to be the increase in WUE. This improvement probably explains the positive increase of photosynthesis and biomass accumulation presented by U. brizantha and M. maximus, respectively. The increase in temperature affected leaf carbohydrate content of M. maximus by reducing sucrose, glucose and fructose content. These reductions were not related to thermal stress since photosynthesis and growth were not harmed. Cellulose content was not affected in any of the three species, just the lignin content in U. decumbens and M. maximus. All treatments promoted lignin content reduction in U. brizantha, suggesting a delay in leaf maturation of this species. Together, the results indicate that climate change may differentially promote changes in leaf gas exchanges, carbohydrate content and growth in C4 plant species studied and all of them could benefit in some way from these changes, constituting a threat to the native Cerrado biodiversity.

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Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.

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Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.(AU)

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Lilium pumilum is a species that stands out in floriculture for presenting orange inflorescences that attract the consumer. This study thus aimed at characterizing the carbohydrate metabolism of floral structures of L. pumilum in different development stages. For this purpose, carbohydrate levels (total soluble sugars, reducing sugars, non-reducing sugars, and starch), at different floral stages (E0 - bud with no color; E1 - bud at early coloring; E2 - orange bud; E3 - open flower; E4 - senescent flower) were quantified after extraction with ethanol. Lilium pumilum flowers showed high energy potential during floral opening and senescence; total soluble sugars were the main carbohydrates present in the species, reducing with the floral development, and the same occurred with the non-reducing sugar and starch contents. The reducing-sugar content increased with the floral stages. Therefore, this species presents great mobilization of compounds, which are utilized in the production of energy that is employed in floral opening.(AU)

Lilium pumilum é uma espécie que se destaca na floricultura, por apresentar inflorescências alaranjadas que atraem o consumidor. Assim, este trabalho teve como objetivo caracterizar o metabolismo de carboidrato de estruturas florais de L. pumilum em diferentes estádios de desenvolvimento. Para isso, os níveis de carboidratos (açúcares solúveis totais, açúcares redutores, açúcares não redutores e amido), em diferentes estádios florais (E0 - botão sem coloração; E1 - botão em início de coloração; E2 - botão alaranjado; E3 - flor aberta; E4 - flor senescente), foram quantificados a partir da extração com etanol. As flores de L. pumilum apresentaram um alto potencial energético durante a abertura floral e senescência, sendo os açúcares solúveis totais os principais carboidratos presentes na espécie, mas com redução de acordo com o desenvolvimento floral, o mesmo ocorrendo com os teores de açúcar não redutor e amido. O conteúdo de açúcar redutor foi crescente entre os estádios florais. Portanto, a espécie apresenta grande mobilização de compostos, os quais são utilizados na produção de energia, que é empregada na abertura floral.(AU)

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ABSTRACT: Lilium pumilum is a species that stands out in floriculture for presenting orange inflorescences that attract the consumer. This study thus aimed at characterizing the carbohydrate metabolism of floral structures of L. pumilum in different development stages. For this purpose, carbohydrate levels (total soluble sugars, reducing sugars, non-reducing sugars, and starch), at different floral stages (E0 - bud with no color; E1 - bud at early coloring; E2 - orange bud; E3 - open flower; E4 - senescent flower) were quantified after extraction with ethanol. Lilium pumilum flowers showed high energy potential during floral opening and senescence; total soluble sugars were the main carbohydrates present in the species, reducing with the floral development, and the same occurred with the non-reducing sugar and starch contents. The reducing-sugar content increased with the floral stages. Therefore, this species presents great mobilization of compounds, which are utilized in the production of energy that is employed in floral opening.

RESUMO: Lilium pumilum é uma espécie que se destaca na floricultura, por apresentar inflorescências alaranjadas que atraem o consumidor. Assim, este trabalho teve como objetivo caracterizar o metabolismo de carboidrato de estruturas florais de L. pumilum em diferentes estádios de desenvolvimento. Para isso, os níveis de carboidratos (açúcares solúveis totais, açúcares redutores, açúcares não redutores e amido), em diferentes estádios florais (E0 - botão sem coloração; E1 - botão em início de coloração; E2 - botão alaranjado; E3 - flor aberta; E4 - flor senescente), foram quantificados a partir da extração com etanol. As flores de L. pumilum apresentaram um alto potencial energético durante a abertura floral e senescência, sendo os açúcares solúveis totais os principais carboidratos presentes na espécie, mas com redução de acordo com o desenvolvimento floral, o mesmo ocorrendo com os teores de açúcar não redutor e amido. O conteúdo de açúcar redutor foi crescente entre os estádios florais. Portanto, a espécie apresenta grande mobilização de compostos, os quais são utilizados na produção de energia, que é empregada na abertura floral.

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We evaluated 23 tree tomato (Solanum betaceum) accessions from five cultivar groups and one wild relative (Solanum cajanumense) for 26 composition traits. For all traits we found highly significant differences (P<0.001) among the materials studied. The high diversity found within S. betaceum for composition traits was matched by a high diversity within each of the cultivar groups. We found that sucrose and citric acid were the most important soluble sugar and organic acid, respectively, in tree tomato. Fruit in the anthocyanin pigmented (purple) group had a carotenoid content similar to that in the yellow-orange cultivar groups. Total phenolic content was significantly correlated (r=0.8607) with antioxidant activity. Analyses of mineral content showed that tree tomato is a good source of K, Mg, and Cu. Multivariate principal components analysis (PCA) confirmed that an important diversity exists within each cultivar group. The results we have obtained indicate that the high diversity found within the tree tomato could be exploited for selection and breeding for developing the tree tomato as a commercial crop.

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The analysis of ion uptake kinetics is the key experimental procedure for determining the uptake efficiency of different species and varieties. The principal goal of this study was to evaluate phosphorus (P) uptake and its effect on nitrogen (N) metabolism in two maize varieties (Sol da Manhã and Eldorado) and one improved maize cultivar (AG 122®) exposed to a resupply of 10 or 100 μM of P following a period of P deprivation. The experiment was based on a completely randomized design with four replicates, with treatments arranged in a 3x2 factorial scheme consisting of three genotypes and two P doses. The treatments were applied at 16 days after germination (DAG), and samples of nutrient solution were collected over time to estimate the kinetics of P uptake (Vmax, KM and Cmin). At the end of the experiment, a portion of the total fresh weight was stored to determine N fractions and soluble sugars. Under the experimental conditions, the AG 122® cultivar showed the lowest KM and Cmin values for both P doses, indicating a higher uptake efficiency for these plants. In contrast, the Eldorado and Sol da Manhã varieties showed the highest Vmax values. An absence of P from the nutrient solution for one day, followed by the addition of 10 μM of P for the same period, did not result in alterations in N metabolism in any of the genotypes. However, it was observed that the Sol da Manhã and Eldorado varieties concentrated their NO3--N metabolism in their roots, whereas the AG 122® cultivar concentrated its NO3--N metabolism in its shoots.(AU)

A análise das variáveis cinéticas de absorção de íons é o principal procedimento experimental para a diferenciação da eficiência de absorção entre espécies e variedades. Baseado nisso, o objetivo desse trabalho foi avaliar a absorção de fósforo (P) e o seu efeito no metabolismo de nitrogênio (N) em variedades (Sol da Manhã e Eldorado) e cultivar (AG 122®) de milho (Zea mays L.) submetidos ao ressuprimento com 10 e 100 μM de P. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 3x2, sendo três genótipos e dois níveis de P. Aos 16 dias após a germinação (DAG) foram aplicados os tratamentos e procedeu-se a coleta da solução nutritiva ao longo do tempo para estimar as variáveis cinéticas de absorção de P (Vmáx, KM e Cmín) e na coleta final parte da massa fresca total foi armazenada para determinação das frações nitrogenadas e açúcares solúveis. Nas condições do experimento, a cultivar AG 122® apresentou o menor valor de KM e Cmín nas duas doses de P, o que indica uma maior eficiência de absorção por essas plantas, enquanto as variedades Eldorado e Sol da Manhã apresentaram os maiores valores de Vmáx. A omissão de P da solução nutritiva por um dia, seguido da adição de uma dose de 10 μM desse nutriente por igual período não provocou alterações no metabolismo de N entre os genótipos estudados, no entanto, foi observado que as variedades Sol da manhã e Eldorado têm preferência para o metabolismo de N-NO3- na raiz quando comparadas a cultivar AG 122® que o faz preferencialmente na parte aérea.(AU)

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The analysis of ion uptake kinetics is the key experimental procedure for determining the uptake efficiency of different species and varieties. The principal goal of this study was to evaluate phosphorus (P) uptake and its effect on nitrogen (N) metabolism in two maize varieties (Sol da Manhã and Eldorado) and one improved maize cultivar (AG 122®) exposed to a resupply of 10 or 100 μM of P following a period of P deprivation. The experiment was based on a completely randomized design with four replicates, with treatments arranged in a 3x2 factorial scheme consisting of three genotypes and two P doses. The treatments were applied at 16 days after germination (DAG), and samples of nutrient solution were collected over time to estimate the kinetics of P uptake (Vmax, KM and Cmin). At the end of the experiment, a portion of the total fresh weight was stored to determine N fractions and soluble sugars. Under the experimental conditions, the AG 122® cultivar showed the lowest KM and Cmin values for both P doses, indicating a higher uptake efficiency for these plants. In contrast, the Eldorado and Sol da Manhã varieties showed the highest Vmax values. An absence of P from the nutrient solution for one day, followed by the addition of 10 μM of P for the same period, did not result in alterations in N metabolism in any of the genotypes. However, it was observed that the Sol da Manhã and Eldorado varieties concentrated their NO3--N metabolism in their roots, whereas the AG 122® cultivar concentrated its NO3--N metabolism in its shoots.

A análise das variáveis cinéticas de absorção de íons é o principal procedimento experimental para a diferenciação da eficiência de absorção entre espécies e variedades. Baseado nisso, o objetivo desse trabalho foi avaliar a absorção de fósforo (P) e o seu efeito no metabolismo de nitrogênio (N) em variedades (Sol da Manhã e Eldorado) e cultivar (AG 122®) de milho (Zea mays L.) submetidos ao ressuprimento com 10 e 100 μM de P. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 3x2, sendo três genótipos e dois níveis de P. Aos 16 dias após a germinação (DAG) foram aplicados os tratamentos e procedeu-se a coleta da solução nutritiva ao longo do tempo para estimar as variáveis cinéticas de absorção de P (Vmáx, KM e Cmín) e na coleta final parte da massa fresca total foi armazenada para determinação das frações nitrogenadas e açúcares solúveis. Nas condições do experimento, a cultivar AG 122® apresentou o menor valor de KM e Cmín nas duas doses de P, o que indica uma maior eficiência de absorção por essas plantas, enquanto as variedades Eldorado e Sol da Manhã apresentaram os maiores valores de Vmáx. A omissão de P da solução nutritiva por um dia, seguido da adição de uma dose de 10 μM desse nutriente por igual período não provocou alterações no metabolismo de N entre os genótipos estudados, no entanto, foi observado que as variedades Sol da manhã e Eldorado têm preferência para o metabolismo de N-NO3- na raiz quando comparadas a cultivar AG 122® que o faz preferencialmente na parte aérea.

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Photosynthesis was compared in three altitudinal populations of Espeletia schultzii: 3,100, 3,550 and 4,200 masl. The measured parameters were Rubisco activity (EC 4.1.139), chlorophyll, soluble protein and soluble sugars contents, and specific leaf area (SLA). The 4,200 m population had a higher Rubisco activity (at 4 degrees C) followed by those at 3,550 m and 3,100 m. There were no significant differences between populations at 3,100 m and 3,550 m (ANOVA), but their activities were different from those of the 4,200 m population. Chlorophyll a content decreased slightly with elevation, while chlorophyll b was constant; therefore, the Ra/b ratio decreased with elevation, but not significantly. The leaf soluble sugars content increased along the altitudinal gradient. Leaf protein content did not differ. The SLA decreased with altitude. The increase in Rubisco activity might reflect higher enzyme activation and not higher enzyme protein. The increase in soluble sugars is probably associated to Rubisco activity. Three out of the five measured parameters revealed differences with altitude, suggesting a compromise between a higher metabolic activity and a smaller cellular volume.

Se establece una comparación de algunos parámetros fotosintéticos: actividad Rubisco (Ribulosa 1, 5-bis-fosfato carboxilasa EC 4.1.1.39) contenidos de clorofilas, azúcares solubles totales y proteínas solubles totales y área foliar específica (AFE), en tres poblaciones altitudinales de Espeletia schultzii ubicadas a 3 100, 3 550 y 4 200 msnm. De acuerdo con el análisis de varianza la población a 4 200 m presentó una actividad Rubisco significativamente mayor que las otras dos, en cuyos casos los valores no fueron diferentes. Los contenidos de clorofila a presentan una leve tendencia a la disminución con la altura; mientras que la clorofila b se mantiene constante, razón por la cual la relación a/b (R a/b) disminuye con la elevación, aunque, las diferencias no son significativas. El contenido de azúcares en cada una de las poblaciones estudiadas (gm-2), aumenta con la elevación; las diferencias entre las poblaciones son significativas. Con relación al contenido de proteínas, no existen diferencias entre las poblaciones estudiadas. El área foliar específica (AFE) disminuye significativamente con la altura. Es probable que el incremento en la actividad Rubisco sea producido por una mayor activación de la enzima y no por el mayor contenido de proteína. Los azúcares solubles presentan incremento significativo, este hecho es probable que se encuentre asociado con la actividad Rubisco. De los cinco parámetros fotosintéticos medidos, tres presentan diferencias significativas asociadas con la altitud. Esto representa un compromiso entre una mayor actividad metabólica mantenida en un menor volumen celular.

Asunto(s)

RESUMEN

Caesalpinia echinata seeds stored in laboratory environmental conditions lose their viability in one month whilst under low temperatures germination is maintained for 18 months of storage. These seeds are tolerant to desiccation, keeping their viability up to 0.08 gH2O.gDW-1. Since soluble carbohydrates are believed to be involved with desiccation tolerance and seed storability, the aim of this work is to analyze the content and composition of soluble carbohydrates in C. echinata seeds during storage in paper bags (PB) and glass flasks (GF) at laboratory room (RT) and cool (CT) temperatures. In freshly harvested seeds, total soluble carbohydrates comprised approximately 10% of the dry weight, decreasing to ca. 8% over 18 months of storage at RT. In seeds stored at CT, sugars varied differently decreasing initially and being restored at the end of the analysis period. The main neutral sugars in seeds from all treatments were sucrose, fructose and glucose. Raffinose and stachyose were present as traces. Free myo-inositol and other cyclitols were also detected. The main tendency observed was the variation in levels of both glucose and fructose in relation to sucrose, the highest levels of monosaccharides which were found in seeds stored at CT. The values of glucose and fructose were practically constant in seeds stored in paper bags for 18 months at CT, decreasing consistently in the other treatments, mainly at RT. Sucrose contents remained relatively stable. Changes in soluble sugars during storage suggest that the loss of germinability of seeds of C. echinata could be associated with low levels of glucose and fructose in relation to sucrose.

Sementes de Caesalpinia echinata (pau-brasil) perdem a viabilidade em um mês quando armazenadas no ambiente de laboratório, enquanto a capacidade germinativa é mantida quando armazenadas sob temperturas baixas. O presente trabalho teve como objetivos analisar o conteúdo e a composição dos carboidratos de sementes de C. echinata armazenadas em câmara fria (CT) e em temperatura ambiente do laboratório (RT), em duas embalagens distintas (permeável e impermeável), visando a avaliar o envolvimento desses compostos com a capacidade germinativa das sementes. Os resultados mostraram que os carboidratos solúveis são constituídos principalmente de sacarose, glicose, frutose, myo-inositol e traços de rafinose e estaquiose, totalizando cerca de 10% da massa seca das sementes. As variações nos carboidratos solúveis foram semelhantes nos dois tipos de embalagem, mas diferentes quanto à temperatura de armazenamento. Em CT, as proporções dos monossacarídeos encontradas nas sementes recém-colhidas foram mantidas por cerca de 18 meses de armazenamento, coincidindo com alta porcentagem de germinação (80%). Nas armazenadas em RT houve redução expressiva nas proporções de glicose e frutose e perda completa da germinabilidade. O conteúdo de sacarose se manteve relativamente estável durante todo o período de análise. Os resultados indicam que a perda da germinabilidade de sementes de C. echinata está associada à diminuição dos níveis de glicose e frutose em relação aos níveis de sacarose.

RESUMEN

Caesalpinia echinata seeds stored in laboratory environmental conditions lose their viability in one month whilst under low temperatures germination is maintained for 18 months of storage. These seeds are tolerant to desiccation, keeping their viability up to 0.08 gH2O.gDW-1. Since soluble carbohydrates are believed to be involved with desiccation tolerance and seed storability, the aim of this work is to analyze the content and composition of soluble carbohydrates in C. echinata seeds during storage in paper bags (PB) and glass flasks (GF) at laboratory room (RT) and cool (CT) temperatures. In freshly harvested seeds, total soluble carbohydrates comprised approximately 10% of the dry weight, decreasing to ca. 8% over 18 months of storage at RT. In seeds stored at CT, sugars varied differently decreasing initially and being restored at the end of the analysis period. The main neutral sugars in seeds from all treatments were sucrose, fructose and glucose. Raffinose and stachyose were present as traces. Free myo-inositol and other cyclitols were also detected. The main tendency observed was the variation in levels of both glucose and fructose in relation to sucrose, the highest levels of monosaccharides which were found in seeds stored at CT. The values of glucose and fructose were practically constant in seeds stored in paper bags for 18 months at CT, decreasing consistently in the other treatments, mainly at RT. Sucrose contents remained relatively stable. Changes in soluble sugars during storage suggest that the loss of germinability of seeds of C. echinata could be associated with low levels of glucose and fructose in relation to sucrose.

Sementes de Caesalpinia echinata (pau-brasil) perdem a viabilidade em um mês quando armazenadas no ambiente de laboratório, enquanto a capacidade germinativa é mantida quando armazenadas sob temperturas baixas. O presente trabalho teve como objetivos analisar o conteúdo e a composição dos carboidratos de sementes de C. echinata armazenadas em câmara fria (CT) e em temperatura ambiente do laboratório (RT), em duas embalagens distintas (permeável e impermeável), visando a avaliar o envolvimento desses compostos com a capacidade germinativa das sementes. Os resultados mostraram que os carboidratos solúveis são constituídos principalmente de sacarose, glicose, frutose, myo-inositol e traços de rafinose e estaquiose, totalizando cerca de 10% da massa seca das sementes. As variações nos carboidratos solúveis foram semelhantes nos dois tipos de embalagem, mas diferentes quanto à temperatura de armazenamento. Em CT, as proporções dos monossacarídeos encontradas nas sementes recém-colhidas foram mantidas por cerca de 18 meses de armazenamento, coincidindo com alta porcentagem de germinação (80%). Nas armazenadas em RT houve redução expressiva nas proporções de glicose e frutose e perda completa da germinabilidade. O conteúdo de sacarose se manteve relativamente estável durante todo o período de análise. Os resultados indicam que a perda da germinabilidade de sementes de C. echinata está associada à diminuição dos níveis de glicose e frutose em relação aos níveis de sacarose.

RESUMEN

Irradiance is a crucial factor in plant development. Different radiant energy levels cause different responses related to plant growth and the production and distribution of dry matter. Considering the relationship between light availability and metabolism of carbohydrates and derived compounds, the aim of this work was to assess the effects of irradiance on non-structural carbohydrate contents and composition, as well as on the hypoglycemiant activity of Rhynchelytrum repens, a pantropical grass species popularly used for diabetes treatment. Plants of R. repens growing under natural irradiance (NI) showed increased content of total soluble carbohydrate (TSC), higher fluctuations in starch content (SC) and higher number of tillers. The flowering process of these plants was preceded by an increase in sucrose. However, their water content was low when compared to that of plants cultivated under low irradiance (LI). The ratio root/aerial organs and SC showed no significant differences in plants grown under LI, although TSC increased and a lower number of tillers were observed during the experimental period. In both conditions, sucrose was the ubiquitous sugar and seemed to be involved in the flowering process. A reduction in the blood sugar level was observed through the intra-peritoneal (IP) administration of the precipitate of aqueous extracts obtained from plants growing in both conditions of light; the supernatant fraction showed no hypoglycemic effect.

A irradiância é um fator crucial em reações vitais para o crescimento e desenvolvimento das plantas. A utilização da energia radiante pelos vegetais afeta diferentes respostas em relação ao padrão de desenvolvimento e à produção de matéria seca e sua conseqüente distribuição. Tendo em vista a intrínseca relação entre disponibilidade de luz, acúmulo de biomassa e metabolismo de carboidratos e compostos relacionados, os objetivos deste trabalho foram avaliar o efeito da irradiância sobre o conteúdo e a composição dos carboidratos não-estruturais, sobre o desenvolvimento e sobre a atividade hipoglicemiante de Rhynchelytrum repens, uma gramínea pantropical de origem africana utilizada popularmente no tratamento de diabetes. O cultivo a pleno sol (PS) estimulou aumento no conteúdo de carboidratos solúveis totais (CST), no perfilhamento das plantas e nas flutuações do conteúdo de amido (CA). O florescimento dessas plantas foi precedido por um aumento de CST, especialmente de sacarose. Foi observado também menor conteúdo de água nas plantas sob PS quando comparado com as plantas cultivadas sob irradiância reduzida (IR). Nesta última condição, o CA e a razão raiz/parte aérea não sofreram alterações significativas, porém houve aumento no conteúdo de CST ao longo do período experimental, menor grau de perfilhamento e formação de raízes adventícias aéreas. Em ambas as condições de luminosidade, a sacarose foi o açúcar mais abundante e com maiores variações. Esse açúcar parece estar envolvido nos processos de florescimento da espécie. Uma redução no nível de glicose plasmática foi observada a partir da administração do precipitado do extrato aquoso de R. repens obtido de plantas cultivadas em PS e IR, não havendo diferença significativa entre os tratamentos. A fração sobrenadante não apresentou efeito hipoglicemiante.