Abstract The main factors governing Hevea brasiliensis germination and seedling establishment remains unclear. We examined the effect of growth regulators Indole 3-Acetic Acid (IAA) and 6-Benzylaminopurine (BAP), and their interactions on germination and the development of mature zygotic embryos (MZE) and protein profile of Hevea brasiliensis seedlings from wild and cultivated (clone PB 250) genotypes. Embryonic axes excised from seeds (wild and clone PB 250) were inoculated in Murashige and Skoog medium (control) and supplemented with IAA (3 µM) and BAP (6 µM) individually and their combination (3 µM IAA + 6 µM BAP). For both genotypes, the mature embryos displayed a high percentage of germination and establishment, and the seedlings were characterized by protein bands ranging from 7 to 30 kDa. Notably, the wild genotype showed proteins in the 14 kDa range, which may be associated with one of the major rubber elongation factors (REF). The wild and clone genotypes presented different behavior and strategies in relation to the protein profile in the presence of different growth regulators. Although the latex biosynthetic pathway and its mechanisms of regulation still remain largely unknown, our results aid in our understanding of the dynamics of proteins in different rubber tree clones in vitro.

RESUMO O objetivo do trabalho foi avaliar o crescimento do tomateiro cultivar Upiã nos sistemas de cultivo Vertical, Cerca Cruzada e Viçosa, visando obter esclarecimento para os ganhos produtivos alcançados no sistema Viçosa. O experimento foi conduzido em Viçosa-MG, no período de 21 de agosto a 05 de dezembro de 2012, no esquema de parcelas subdivididas, sendo as parcelas representadas pelos sistemas de cultivo: Vertical, tutorado com fitilho em espaçamento 1,0 x 0,5 m; Cerca Cruzada, tutorado com bambu em espaçamento de 1,0 x 0,5 m; e Viçosa, tutorado com fitilho em espaçamento 2,0 x 0,2 m. As subparcelas foram compostas pelas épocas de amostragem das plantas: 15, 30, 45, 60 e 75 dias após o transplantio. O delineamento experimental foi em blocos casualizados, com quatro repetições. Cada parcela foi constituída por três linhas de 10 plantas, perfazendo um total de 30 plantas por parcela, sendo avaliadas as quatro plantas centrais de cada parcela. Avaliou-se matéria seca de folhas (MSF), caule (MSC), inflorescências (MSI), frutos (MSFr) e total (MST). Utilizando-se a área foliar, medida em escâner digital, e as massas secas previamente obtidas, foram determinados os seguintes índices fisiológicos de crescimento: índice de área foliar (IAF), área foliar específica (AFE), taxa de crescimento relativo (TCR) e taxa assimilatória líquida (TAL). O sistema Viçosa alterou o padrão de crescimento do tomateiro, quantificado pela análise de crescimento, em relação ao Cerca Cruzada e Vertical. O prolongamento da segunda fase de crescimento para a matéria seca de frutos, possivelmente, explicaria os ganhos produtivos obtidos no Sistema Viçosa. Estudos adicionais são necessários para esclarecer a relação entre a duração da 2a fase de crescimento da matéria seca de frutos, os índices fisiológicos AFE, IAF e TAL com o tamanho e produção de frutos do tomateiro.

ABSTRACT The objective of this work was to analyze the growth of the Upiã tomato cultivar in the Vertical, Crossed Fence and Viçosa cultivation systems, in order to obtain explanations for the productive gains achieved in the Viçosa system. The experiment was conducted in Viçosa, Minas Gerais State, Brazil, from August 21st to December 5th, 2012, in the scheme of subdivided plots, being the plots represented by the cultivation systems: Vertical, using tape, 1.0×0.5 m spacing; Crossed Fence, staked with bamboo, 1.0x0.5 m spacing; and Viçosa, using tape, 2.0x0.2 m spacing. The subplots were composed by the sampling times of the plants: 15, 30, 45, 60 and 75 days after transplanting. The experimental design was in randomized blocks, with four replications. Each plot was composed by three lines of 10 plants, making a total of 30 plants per plot, being evaluated the four central plants of each plot. We evaluated the dry matter of leaves (MSF), stem (MSC), inflorescences (MSI), fruits (MSFr) and total (MST). Using the foliar area index, measured by digital scanners and the previously obtained dry masses, we determined the physiological growth indices: foliar area index (IAF), specific foliar area (AFE), relative growth rate (TCR), and net assimilation rate (TAL). The Viçosa system altered the growth pattern of the tomato, quantified by the growth analysis, in comparison to Crossed and Vertical Fences. The prolongation of the second growth phase for the dry matter of fruits could possibly explain the productive gains obtained in the Viçosa system. Additional studies are required in order to clarify the relationship between the duration of the second phase of fruit dry matter growth, the physiological indexes AFE, IAF and TAL with the size and fruit yield of the tomato.

Abstract Cyanobacteria is a remarkable group of prokaryotic photosynthetic microorganisms, with several genera capable of fixing atmospheric nitrogen (N2) and presenting a wide range of morphologies. Although the nitrogenase complex is not present in all cyanobacterial taxa, it is spread across several cyanobacterial strains. The nitrogenase complex has also a high theoretical potential for biofuel production, since H2 is a by-product produced during N2 fixation. In this review we discuss the significance of a relatively wide variety of cell morphologies and metabolic strategies that allow spatial and temporal separation of N2 fixation from photosynthesis in cyanobacteria. Phylogenetic reconstructions based on 16S rRNA and nifD gene sequences shed light on the evolutionary history of the two genes. Our results demonstrated that (i) sequences of genes involved in nitrogen fixation (nifD) from several morphologically distinct strains of cyanobacteria are grouped in similarity with their morphology classification and phylogeny, and (ii) nifD genes from heterocytous strains share a common ancestor. By using this data we also discuss the evolutionary importance of processes such as horizontal gene transfer and genetic duplication for nitrogenase evolution and diversification. Finally, we discuss the importance of H2 synthesis in cyanobacteria, as well as strategies and challenges to improve cyanobacterial H2 production.

Tubérculos de batata das cultivares Eliza, Pérola e Atlantic foram armazenados a 2ºC durante 10 dias e, posteriormente, recondicionados a 15ºC por 10 ou 20 dias, de forma a verificar a eficiência destes tratamentos em reverter o adoçamento associado ao armazenamento a baixas temperaturas. O recondicionamento foi associado a uma redução nos teores de sacarose em todas cultivares, uma redução na atividade da sacarose-fosfato sintase e UDP-glicose pirofosforilase. Houve também redução na atividade da sacarose sintase, e redução temporária na atividade da invertase, o que não aconteceu de uma forma homogênea entre as cultivares. O recondicionamento também reduziu o teor de glicose, mas somente nas cultivares Pérola e Atlantic. Esta redução foi linear com o tempo de recondicionamento, o que sugere que maior redução do adoçamento possa ser observada com a utilização de períodos maiores de recondicionamento. Não foi observada alteração no teor de amido, embora tenha ocorrido redução temporária nas atividades da amido fosforilase e amidolítica total em algumas cultivares. Em conjunto, esses dados demonstram que o recondicionamento, mesmo por curtos períodos de tempo (20 dias) ou temperaturas mais amenas (15ºC), resulta em alterações metabólicas heterogêneos em diferentes cultivares, e que podem contribuir significativamente para a redução do adoçamento de tubérculos nas cultivares Pérola e Atlantic.

Potato tubers of cultivars Atlantic, Eliza and Pérola were firstl stored at 2ºC for 10 days and then reconditioned at 15ºC for 10 or 20 days, in order to verify if these treatments could reduce the cold-sweetening. The reconditioning was associated to reduced tuber sucrose levels in all cultivars analyzed, and was followed by a clear reduction in the activity of sucrose-phosphate syntase, UDP-glucose pyrophosphorylase, and sucrose synthase. The decrease in invertase activity was only transient, and limited to some genotypes. These treatments also reduced linearly the glucose levels in Pérola and Atlantic tubers, which in turn suggest that stronger reductions could be observed under longer reconditioning periods. Starch contents were not changed in reconditioned tubers, although a transient decrease in the activity of starch phosphorylase and total amidolitic activity was observed in some genotypes. These data indicate that reconditioning, even under short time periods (20 days) and mild temperatures (15°C), result in a strong and heterogeneous effect on tuber carbohydrate metabolism. More importantly, these results indicate that the reconditioning could reduce cold-sweetening in the cultivars Pérola and Atlantic.