RESUMOEstudos sobre a atividade microbiológica que ocorre na rizosfera de diversos vegetais levaram ao descobrimento de grupos de microrganismos importantes para o desenvolvimento vegetal. Dentre eles estão as rizobactérias que são capazes de colonizar as raízes, estimulando-a diretamente ou beneficiando o crescimento e o desenvolvimento de diversas plantas. Estas bactérias são chamadas Rizobactérias Promotoras de Crescimento em Plantas (RPCP). Este trabalho teve o objetivo de isolar, identificar, testar a capacidade da solubilização de fosfato e a produção de ácido indol acético (AIA) de bactérias que habitam a rizosfera de plantas de milho. A análise parcial do gene 16S rRNA dos 58 isolados possibilitou a identificação dos gêneros, Bacillus, Burkholderia e Azospirillum, sendo os mais frequentes totalizando 68% dos isolados, seguidos de Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea , Bosea. Desses, 27 apresentaram a capacidade de solubilização do fosfato e 18 foram positivos no teste colorimétrico para detecção de produção do AIA. A partir destes resultados, selecionou-se um organismo pertencente ao gênero Sphingomonas para ser testado em casa de vegetação como promotor de crescimento com as estirpes de Azospirillum brasilense (AbV5 e AbV6). As plantas foram avaliadas quanto à altura aos vinte e setenta dias após a germinação e a massa seca da parte aérea (MSPA)e parte radicular (MSPR) foi quantificada após setenta dias no encerramento do experimento. Os resultados das análises do isolado pertencente ao gênero Sphingomonas foram estatisticamente semelhantes às estirpes AbV5 e AbV6 na planta de milho indicando que este microrganismo possui potencial para ser utilizado como RPCP. Palavras-chaves: RPCP, ácido indol acético, solubilização de fosfato, Sphingomonas spp. ABSTRACT IDENTIFICATION AND EVALUATION OF BACTERIA ISOLATED FROM ROOTS OF MAIZEResearches about microbiological activity on many plants rizosphere led to the discovery of groups of important microrganisms for plants development. Among them there are the rizobacteria able to colonize the roots, stimulating directly or benefiting many plants. These bacteria are called Growth Promoting Rizobacteria or GPR. In view of this, the present study was performed, aiming to isolate, identify and test phosphate solubilization and acetic indol acid (AIA) production in bacteria that lives in maize roots. The partial analysis of the 16S rRNA gene of the 58 isolates enabled the identification of the genres Bacillus, Burkholderia and Azospirillum, and the most frequent totaling 86% of the isolates, followed by Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea and Bosea. Out of the 58 isolates, 27 showed the capacity of phosphate solubilization and 18 were positive to the AIA production colorimetric detection test. From these results was chosen an organism belonging to the genre Sphingomonas to be tested at greenhouse as growth promoter with the strains Azospirillum brasiliense (AbV5 e AbV6). The plants were assessed twenty and seventy days after germination. Dry ...

SUMMARYAuxin-producing bacteria inhabit the roots of orchids and can bring benefits to the host plant. Plants of this family are multiplied by in vitro assimbiotic conditions and little is known about the role of these microorganisms for ex vitro acclimatization. Four auxin-producing rhizobacteria isolated from the specie Cattleya walkeriana were evaluated for their ability to promote survival and growth of in vitro germinated plantlets during ex vitro acclimatization. Partial sequencing of the 16S rRNA genes of bacteria cultures from root velamen of this epiphytic species identified them as Bacillus, Burkholderia, Enterobacter and Curtobacterium. The presence of indole compounds in the filtered supernatants of liquid cultures was quantified by colorimetric assay and confirmed by HPLC. Indole-3-lactic acid (ILA) and indole-3-acetaldehyde (IAAld) were present in high quantities, except in Enterobacter sp. cultures, where in indole-3-acetic acid (IAA) and indole-3-pyruvic acid (IPA) were more prevalent. These rhizobacteria were inoculated into asymbiotically-germinated plantlets of the host orchid, acclimatized in greenhouse for 90 days and assessed for their growth-promoting ability. The lowest ability to promote growth was observed for Burkholderia sp. and Curtobacterium sp., while Bacillus sp. and Enterobacter sp. improved growth in all evaluated characteristics and increased the percentage of plantlet survival. This

IVCrescimento in vitro e aclimatização de Cattleya loddigesii Lindley (Orchidaceae) com carvão ativado sob dois espectros luminosos

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RESUMOO presente estudo teve por objetivo analisar os aspectos da germinação e avaliar o efeito de concentrações de sacarose no crescimento in vitro de Cattleya violacea. Sementes provenientes de cápsulas fechadas foram semeadas em meio de cultura Murashige e Skoog (MS) e a morfologia externa da semente à plântula foi fotodocumentada em estereomicroscópio e microscópio eletrônico de varredura. Plântulas com 90 dias após a semeadura foram repicadas em meio de cultura ½ MS (com metade da concentração de macronutrientes) com diferentes concentrações de sacarose (0, 10, 20, 30 e 40 g L -1 ), incubadas nas mesmas condições in vitro por mais 150 dias e em seguida as plântulas foram avaliadas quanto ao número de raízes, comprimento da maior raiz, número de folhas, comprimento da parte aérea, massa fresca e seca total. Os dados biométricos foram submetidos à análise estatística e a eles ajustadas curvas de regressão. As sementes apresentaram testa reticulada com uma extremidade micropilar (aberta) e calazal (fechada); o embrião originou uma estrutura tuberiforme clorofilada denominada protocormo que pode apresentar rizóides, folíolos e quando provido de raiz é considerado plântula. A ausência de açúcar ou a maior concentração avaliada de sacarose foram prejudiciais ao crescimento da planta. A concentração de 27 g L -1 proporcionou maior crescimento in vitro possibilitando maior eficiência para a propagação massal dessa espécie de elevado potencial ornamental. PALAVRAS-CHAVE: Germinação assimbiótica, orquídea nativa, carboidrato. Initial development and in vitro growth of Cattleya violacea (Kunth) Rolfe in different sucrose concentrations ABSTRACTThe aims of this study were to analyze the initial germination aspects and evaluate the effect of sucrose concentrations on in vitro growth of Cattleya violacea. Mature seeds from closed pods were sowed on MS (Murashige and Skoog) culture medium. The external morphology of seed and plantlets were documented by light and scanning electron microscopy. Plantlets with 90 days after sowing were subcultured on ½ MS (with half-strength macronutrients concentrations) culture medium with different sucrose concentrations (0, 10, 20, 30 and 40 g L -1 ), incubated under the same in vitro conditions during more 150 days followed by the evaluation of root number, root length, shoot length, fresh and dry weight. The biometric data were statistically analyzed and regression curves constructed. The seeds showed reticulate seed coat with a micropylar (opened) and chalazal (closed) end; the embryo results a chlorophyllated tuberiforme structure called protocorm, which may have rhizoids, leaflets and is considered plantlet when it has root. Absence of sucrose or the highest evaluated sucrose concentration was detrimental for plant growth. The concentration of 27 g L -1 provided the highest in vitro growth enabling great efficiency for mass propagation of this species of high ornamental potential.

ResumoEste trabalho foi realizado com objetivo de estudar a influência da concentração de sacarose no meio de cultura para o crescimento in vitro e aclimatização da orquídea epífita Cattleya loddigesii. Cinco tratamentos (ausência, 10, 20, 30 e 40g L -1 de sacarose) foram utilizados, em delineamento inteiramente casualizado. A semeadura procedeu-se em meio de cultura ½ MS e, após 90 dias as plântulas de 1,0 +/-0,2 cm foram distribuídas entre os tratamentos, em que permaneceram por mais 90 dias. Após 90 dias da transferência dos explantes para o meio contendo os tratamentos foi avaliado o número de raízes, comprimento da maior raiz, comprimento da parte aérea, comprimento da maior folha, número de folhas, massa de matéria seca total e pigmentos fotossintéticos. A porcentagem de sobrevivência foi aferida 75 dias após a aclimatização das plantas em casa de vegetação. Os dados das variáveis biométricas foram submetidos à análise de variância e regressão polinomial (p<0,05) e para os demais as médias foram comparadas pelo teste de Tukey (p<0,05). A concentração de 20g L -1 de sacarose favoreceu o crescimento in vitro, em todos os parâmetros avaliados, apresentou maior produção de clorofila a, clorofilas totais e carotenóides, além de maior sobrevivência em condições ex vitro. A concentração de 20g L -1 de sacarose no meio de cultura foi a de maior eficiência dentre as concentrações estudadas, tanto para o crescimento in vitro quanto estabelecimento ex vitro de Cattleya loddigesii. Palavras-chave: Micropropagação, carboidrato, orquídea brasileira AbstractThis work aimed to study the influence of sucrose in the culture medium for in vitro growth and acclimatization of the epiphytic orchid Cattleya loddigesii. Five sucrose treatments (absence, 10, 20, 30 and 40g L -1 ) were used in a randomic experimental design. Mature seeds were sowed in ½ MS culture medium and after 90 days the plantlets (1.0 +/-0.2 cm) were inoculated between the treatments, whereby they were remained more 90 days. After 180 days of the beginning of the experiment the plantlets were removed from the flasks and evaluated the number of roots, shoot length, number of leafs, total dry weight and photosynthetic pigments. Survival percentage was evaluated after 75 days of acclimatization. The data of biometric variables were analyzed by Anovaand polynomial regression (p<0.05). Theothers data were submitted to the Anova and the means compared by the Tukey test (p<0.05). The sucrose concentration of 20g L -1 favored the in vitro growth in all evaluated parameters, showed higher production of chlorophyll a, total chlorophyll and carotenoids, in addition to increased

Expression of acid ectophosphatase by Enterobacter asburiae, isolated from Cattleya walkeriana (Orchidaceae) roots and identified by the 16S rRNA gene sequencing analysis, was strictly regulated by phosphorus ions, with its optimal activity being observed at an inorganic phosphate concentration of 7 mM. At the optimum pH 3.5, intact cells released p-nitrophenol at a rate of 350.76 ± 13.53 nmol of p-nitrophenolate (pNP)/min/10(8) cells. The membrane-bound enzyme was obtained by centrifugation at 100,000 × g for 1 h at 4 °C. p-Nitrophenylphosphate (pNPP) hydrolysis by the enzyme follows "Michaelis-Menten" kinetics with V = 61.2 U/mg and K0.5 = 60 μM, while ATP hydrolysis showed V = 19.7 U/mg, K0.5 = 110 μM, and nH = 1.6 and pyrophosphate hydrolysis showed V = 29.7 U/mg, K0.5 = 84 μM, and nH = 2.3. Arsenate and phosphate were competitive inhibitors with K i = 0.6 mM and K i = 1.8 mM, respectively. p-Nitrophenyl phosphatase (pNPPase) activity was inhibited by vanadate, while p-hydroxymercuribenzoate, EDTA, calcium, copper, and cobalt had no inhibitory effects. Magnesium ions were stimulatory (K0.5 = 2.2 mM and nH = 0.5). Production of an acid ectophosphatase can be a mechanism for the solubilization of mineral phosphates by microorganisms such as Enterobacter asburiae that are versatile in the solubilization of insoluble minerals, which, in turn, increases the availability of nutrients for plants, particularly in soils that are poor in phosphorus.

The aim of the present study was to evaluate the effects of carbohydrate supplementation on the propagation of the orchid Cattleya schilleriana. The 120-d-old seedlings were subcultured in fructose-, glucose-, or sucrose-supplemented (0, 15, 30, and 45g L-1) ½ MS culture medium (half-strength macronutrient concentrations), using a completely random design with four repetitions per treatment. After 120d of treatment, root number and length, leaf number and length, and fresh weight were evaluated, and seedling survival was evaluated after 75d of acclimatization in a greenhouse. The in vitro growth data were submitted to regression analysis, whereas the percentage survival data were analyzed using ANOVA and Tukey’s test. Both in vitro growth and ex vitro survival were lowest when the plantlets were grown in the absence of a carbohydrate source and highest (>90% survival) when supplemented with glucose. According to our findings, the addition of either glucose (30g L-1) or sucrose (30g L-1) is recommended for mass propagation of C. schilleriana.