Correlation of biometric characteristics of fruits and seeds with the vigor of Agonandra brasiliensis seedlings in northern Amazonia

The goal of this study was to determine and correlate the main morphometric characteristics of fruits, seeds, and seedling vigor of Agonandra brasiliensis, in Roraima. The design was completely randomized with three treatments, consisting of six replications with 20 seeds. The treatments established were three classes of seeds: T1 - small seeds (S = 1.50-1.69 g); T2 - medium seeds (M = 1.70-1.89 g) and T3 - large seeds (L = 1.90-2.09 g). The variables evaluated were: length; diameter; the fresh mass of fruits and seeds; percentage, speed (in index) and average time of emergence, length of roots and aerial part; number of leaves; fresh, dry and total seedling mass; seedling lignification index; root/shoot ratio and dry root/shoot ratio and correlations between all studied variables. The fresh mass of the fruit of Agonandra brasiliensis has a high positive correlation with the mass of seeds. Small seeds of Agonandra brasiliensis exhibit a higher percentage of emergence in the conditions of the northern Amazon.

Macronutrient uptake, transport and use efficiency in seedlings of Pochota fendleri produced in different substrates / Eficiência de absorção, transporte e utilização de macronutrientes por mudas de Pochota fendleri produzidas em diferentes substratos

Seedlings produced in containers can be influenced by the materials used in the substrate, which affects the robustness of the plants and, indirectly, the time required for transplanting and for the plants to become established in the field. The aim of this study was to determine the chemical properties of different materials and on the absorption of macronutrients in Pochota fendleri seedlings (cedro-doce). The treatments were: sand (Sa), soil (So), sand+soil (Sa+So), and sand+soil+crushed Brazil nut capsules (Sa+So+CNC). The growth and macronutrient content were evaluated at 60 days after thinning. The amount of macronutrients in the substrate increased with the addition of crushed Brazil nut capsules. The use of different materials for the substrate, particularly Sa+So+CNC, had a positive influence on the morphological characteristics of seedlings, which ensuring high rates of establishment and survival after outplanting, making commercial reforestation with Pochota fendleri attractive.

As mudas produzidas em recipientes podem ser influenciadas pelos materiais utilizados no substrato, que afetam a robustez das plantas e, indiretamente, o tempo necessário para o transplante e o estabelecimento das plantas no campo. O objetivo deste estudo foi determinar as propriedades químicas de diferentes materiais e a absorção de macronutrientes em mudas de Pochota fendleri (cedro-doce). Os tratamentos foram: areia (Sa), solo (So), areia + solo (Sa + So) e areia + solo + casca de ouriço da castanha do Brasil triturada (Sa + So + CNC). O crescimento e o teor de macronutrientes foram avaliados 60 dias após o desbaste. A quantidade de macronutrientes no substrato aumentou com a adição de casca de ouriço da castanha do Brasil triturada. O uso de diferentes materiais para o substrato, principalmente o Sa + So + CNC, influenciou positivamente as características morfológicas das mudas, garantindo altas taxas de estabelecimento e sobrevivência após o plantio, tornando atraente o reflorestamento comercial com Pochota fendleri.

Water absorption and method improvement concerning electrical conductivity testing of Acacia mangium (Fabaceae) seeds / Absorción de agua y optimización de métodos para medir la conductividad eléctrica en semillas de Acacia mangium (Fabaceae)

Abstract:Acacia is an important forest species of rapid growth whose seeds have tegument dormancy. In this work it was intended to characterize water absorption pattern after seed dormancy break, and to determine the amount of water, container size and the need of breaking the tegument dormancy, as to perform electrical conductivity test in small and large seeds of Acacia mangium (Fabaceae). The seeds were collected from 10, 8 and 6 years old trees established in poor yielding-capacity soils on savannah areas of Roraima, Brazil; seeds were classified in six lots concerning to seed size and tree age. Germination tests (50 seeds and four replications per lot) were carried out on germitest® paper maintained on gerbox at 25 °C. Imbibition was verified by seed weighing at different times (0, 2, 5, 8, 12, 16, 24, 36, 48, 60, 72, 84, 96 and 120 hours). The electrical conductivity test consisted of three experiments, distinguished by the amount of water used and by the container size in which seeds were immersed. Seeds of A. mangium coming from 10 years old trees presented increased germination percent and germination speed than seeds of six-year old trees. Small seeds presented increased in electrical conductivity and water absorption until 120 hours when compared to large seeds. The immersion of seeds of A. mangium in 40 mL of distilled water into 180 mL plastic containers, after dormancy break, it is indicated for the determination of electrical conductivity test. The ratio of electrolytes by seed mass, after 24 hours of immersion in water, turns electrical conductivity test more accurate concerning A. mangium seeds. Rev. Biol. Trop. 64 (4): 1651-1660. Epub 2016 December 01.

Resumen:Acacia es una importante especie forestal de rápido crecimiento cuyas semillas presentan dormancia del tegumento. En este trabajo se caracterizó el patrón de absorción de agua después de la dormancia y se estableció la cantidad de agua, el tamaño del recipiente y la necesidad de ruptura del tegumento para poder medir la conductividad eléctrica en semillas pequeñas y grandes de Acacia mangium (Fabaceae). Las semillas fueron recolectadas de árboles de 6, 8 y 10 años, clasificadas en grandes o pequeñas y agrupadas en seis grupos. Para la prueba de germinación fueron utilizados cuatro repeticiones de 50 semillas de cada grupo, en papel germitest® a 25 °C. La imbibición se verificó con pesajes en los tiempos 0, 2, 5, 8, 12, 16, 24, 36, 48, 60, 72, 84, 96 y 120 horas con semillas colocadas en papel. La prueba de conductividad eléctrica se realizó en tres experimentos diferenciados por la cantidad de agua utilizada y el tamaño del recipiente de inmersión de las semillas. Las semillas de árboles de 10 años de edad tienen un porcentaje de germinación más alto y mayor velocidad de germinación que semillas de árboles de seis años. Las semillas pequeñas tienen una mayor conductividad eléctrica y mayor porcentaje de absorción de agua en comparación con las semillas grandes, hasta 120 horas. La inmersión de semillas en 40 mL de agua destilada en recipientes plásticos de 180 mL, después de la dormancia, esta indicada para la determinación de la conductividad eléctrica. La lectura de electrolitos en semillas, después de 24 horas de inmersión en agua, hace más precisa la prueba de conductividad eléctrica de semillas de A. mangium.

População microbiana em solo cultivado com soja e tratado com diferentes herbicidas em área de cerrado no estado de Roraima / Microbial population in soil cultivated with soybean and treated with different herbicides in cerrado area of Roraima

Este trabalho objetivou avaliar o impacto de herbicidas à base de glyphosate, imazaquin e trifluralin na biomassa microbiana do solo, na comunidade bacteriana associada ao rizoplano de soja e também na nodulação das plantas de soja. As avaliações foram realizadas por um período de 60 dias, em dois sistemas de manejo do solo: semeadura direta na palha (SD) e semeadura convencional (SC), que receberam a aplicação dos herbicidas glyphosate e, imazaquin e trifluralin, respectivamente. Ao longo do período estudado o imazaquin, na área de SD, ocasionou redução da biomassa microbiana e, também alterou o perfil bacteriano analisado por eletroforese em gel com gradiente desnaturante (DGGE) de forma mais intensa, que o glyphosate. Na área de SC não houve efeito significativo dos herbicidas sobre a biomassa microbiana, tendo ocorrido grande variabilidade entre repetições de um mesmo tratamento nos perfis de DGGE, o que dificultou a observação do efeito dos herbicidas. O seqüenciamento de fragmentos do 16S rDNA retirados dos géis de DGGE mostrou que o glyphosate restringiu o desenvolvimento de uma bactéria com 90 por cento de homologia com Herbaspirillum sp., enquanto, o imazaquin estimulou uma bactéria com 96 por cento de homologia com Ralstonia sp. e, outras bactérias com pelo menos 92 por cento de homologia com Burkholderia, Thiomonas e Pseudomonas não foram afetadas. Também não houve efeito dos herbicidas sobre o número de nódulos nas plantas de soja.

This work aimed to evaluate the impact of glyphosate, imazaquin and trifluralin on soil microbial biomass, on bacteria community associated with soybean rhizoplane and soybean nodulation under two different agricultural management: no-tillage (SD) and conventional tillage (SC). The results showed that imazaquin in SD area lead a significant reduction of soil microbial biomass during the period of evaluation (60 days) and, also had greater modifications in bacterial DGGE profile than the glyphosate treatment. There was no significant effect of herbicides on microbial biomass in SC area, and DGGE profiles presented high variability among replicates of the same treatments, which had difficult the observation of herbicides effects. Some fragments excised from DGGE gels and sequenced indicate that glyphosate interfered in the development of a bacterium with 90 percent of homology to Herbaspirillum sp. 16S rDNA, while another with 96 percent of homology to Ralstonia sp. 16S rDNA was greatly present only in imazaquin treatment, and some others bacteria with more than 92 percent of homology like Burkholderia, Thiomonas and Pseudomonas were not affected by herbicides. Besides that, no significant effect of the herbicides occurred on soybean nodulation.

Avaliação de cultivares de girassol em savana de Roraima / Avaliation of sunflower cultivars in savanna ecosystem of Roraima

A cultura do girassol (Helianthus annuus L.) pode ser conduzida em diversas épocas do ano, destacando-se desta forma, entre as culturas viáveis de serem exploradas nas savanas (lavrados) de Roraima. Entretanto, as cultivares podem apresentar diferenças de adaptação e desenvolvimento dependendo da área de cultivo. Assim, desenvolveu-se este estudo comparativo em área experimental da Embrapa Roraima em 2000, visando avaliar o desempenho de seis cultivares (Agrobel 910; Agrobel 920; Cargill 11; Embrapa 122; Morgan 742; e Rumbosol 91) semeadas em duas épocas (seca, com irrigação suplementar; e chuvosa) em Boa Vista, Roraima. Utilizaram-se parcelas subdivididas num delineamento de blocos ao acaso com quatro repetições, sendo as duas épocas de semeadura em 20 de janeiro e 19 de julho. As subparcelas constaram de quatro fileiras de 6 m, distanciadas de 0,90 m, sendo 0,30 m o espaçamento entre plantas. As cultivares Cargill 11, Rumbosol 91 e Agrobel 910 foram as mais produtivas para cultivo nas condições climáticas das savanas de Roraima, e a semeadura em janeiro é mais indicada, comparada a de julho.