Alana Cristina Dorneles Wandscheer

Interferência alelopática de Raphanus raphanistrum L. sobre a germinação de Lactuca sativa L. e Solanum lycopersicon L.

This article aims at verifying the possible allelopathic effects of Raphanus raphanistrum L. on the germination of lettuce and tomato seeds. For that, we prepare aqueous extracts of nabica leaves and roots. After the leaves and roots were triturated in industrial blender, we diluted the raw extract in distilled water, until the concentrations of five and ten percent (m/v). The germination tests were accomplished by putting twenty-five lettuce and tomato seeds in Petri plates, which were humidified with the obtained extracts, accomplishing four repetitions in each treatment. The control treatment was only watered with distilled water. The seeds were kept in germination camera at twenty-five degrees Celsius for five days. After that period, we observed that all the concentrations of nabica extract reduced the percentage, speed, index of germination speed and radicular length of lettuce seeds, being larger the effect in the treatments with leaves. In tomato seeds, only the ten-percent extract of leaves reduced the germination percentage, radicular and epicotyl length. However, ten-percent extracts of leaves and roots caused delay in the germination process and number of plantules germinated a day, being the ten-percent extract of leaves more active.

Atividade alelopática de folhas e pseudofrutos de Hovenia dulcis Thunb. (Rhamnaceae) sobre a germinação de Lactuca sativa L. (Asteraceae)

Neste trabalho, objetivou-se avaliar o efeito alelopatico de folhas secas e pseudofrutos de Hovenia dulcis Thunb. sobre sementes de alface. Para isso, prepararam-se extratos aquosos de folhas e pseudofrutos nas concentracoes 1, 2 e 4% (m/v). Realizou-se quatro repeticoes de 25 sementes de alface, distribuidas em placas de Petri forradas com papel Germitest e umedecidas com os extratos, mantidas em câmara de germinacao a temperatura de 25°C, fotoperiodo constante e presenca de luz por cinco dias, sendo o controle agua destilada. Calculou-se a porcentagem, a velocidade, o indice de velocidade de germinacao, o comprimento radicular e da parte aerea das plântulas, bem como o efeito das sementes na presenca de diferentes solucoes de pH. Observou-se que as plântulas foram significativamente afetadas na presenca de extratos aquosos de folhas secas e pseudofrutos nas concentracoes 2 e 4%. Os efeitos foram desvinculados do pH e potencial osmotico, indicando, portanto, interferencia alelopatica dos extratos obtidos de Hovenia dulcis.

Competitive ability of corn in coexistence with goosegrass

Competition between plants is one of the main interferences that occurs in agricultural systems and accounts for significant crop yield reductions. The aim of this study was to assess the competitive ability of corn in coexistence with the weed species Eleusine indica. The experiments were conducted in a greenhouse, in the growing season 2010/2011, and were arranged in a completely randomized design with four replications. The experimental units consisted of plastic pots with a volumetric capacity of 8 L. Treatments were arranged in a replacement series with five proportions of corn plants and weed: 100:0, 75:25, 50:50, 25:75, and 0:100, respectively, with a constant population of eight plants per pot, at the end of each treatment. The competitiveness analysis was conducted through diagrams applied to the replacement series experiment and competitiveness index, and the variables evaluated were root, shoot, and total dry mass, and plant height. When in equal proportions, corn showed competitive ability equivalent to goosegrass in relation to the variables shoot, root, and total dry mass. Goosegrass was more competitive than the crop in relation to plant height.

Competitividade de capim-pé-de-galinha com soja

The competition is a negative interference in which individuals compete for environmental resources. The objective was to evaluate the competitiveness of goosegrass with soybean. The experiment was conducted in green-house conditions, in a completely randomized design with four replications. The treatments were five proportions of crop and weed, respectively, 8:0, 6:2, 4:4, 2:6 and 0:8, which corresponded to 100, 75, 50, 25 and 0% of plants soybean and opposite to the goosegrass, which constant population of eight plants per pot (8L), corresponding to approximately 250 plants m-2. The competitiveness analysis was accomplished through diagrams applied to replacement series experiments and competivity index. Soybean showed competitiveness superior to goosegrass for the variables of dry matter, when both were in similar proportions of plants.

Interference of Sorghum sudanense and Eleucine indica in the soybean and corn cultivation

The natural infestations are composed of numerous species that compete for environmental resources such as water, light, nutrients and space. The objective of this study was to evaluate the interference of mixed infestations Sorghum sudanense (sudangrass) and Eleusine indica (goosegrass) in the presence of soybean and corn. The experimental design was completely randomized with four replications and the experimental units consisted of plastic pots with a volume capacity of 8 L. The treatments were associations of plants S. sudanense and E. indica in the proportions 8:0, 6:2, 4:4,2:6 and 0:8, respectively, corresponding to 100, 75, 50, 25 and 0% S. sudanense and the reverse for E. indica. In all treatments remained constant four soybean or corn plants per experimental unit. The variables analyzed in the weeds were shoot dry weight, root, total and height of plants. The competitive analysis was accomplished through diagrams applied to replacement series experiment and indexes of competiveness. The results indicated that E. indica was more competitive than S. sudanense in mixed infestations with corn. Rather, S. sudanense was more competitive than E. indica, in mixed infestations with soybean, demonstrating differences in competitiveness among the weeds.

Interference of soybean and corn with Chloris distichophylla

In nature, plants interact with each other and establish positive, negative, and neutral interference relationships. In agricultural ecosystems, crops are usually affected by competition with weeds, and the effects of this process are influenced by the plant population density and proportional abundance and by the species involved. The present study evaluates the competitive interactions of soybean and corn with Chloris distichophylla. Two experiments were conducted in a greenhouse belonging to the University of Passo Fundo during the 2011/12 crop season: one experiment involving corn and C. distichophylla and another involving soybean and C. distichophylla. The experimental units were plastic pots, and the treatments were based on a replacement series, with a constant total density of eight plants per pot. The treatments included five combinations of soybean or corn plants with the weed species (8:0, 6:2, 4:4, 2:6 and 0:8), corresponding to relative abundances of 100, 75, 50, 25 and 0% of the crop species (and the reverse for the weed species). Competitiveness was analyzed using replacement-series experiment diagrams and competitive indices. Total dry matter and plant height were the two variables analyzed. The competitive indices indicated that corn and soybean crops were more competitive than the weed. The plant height was not affected by competition between both the species.