RESUMO O objetivo deste trabalho foi avaliar a dominância, crescimento e bromatologia do capim-annoni (Eragrostis plana) em área de vegetação secundária. As avaliações foram realizadas aos 23; 45; 64; 86; 111; 132; 153 e 174 dias de crescimento após uma roçada. O capim-annoni foi a espécie dominante na área, representando entre 76 e 90% do total da biomassa. Houve aumento linear na produção de massa seca de folhas (9,8 kg MS ha-1 dia-1) e da parte aérea (16,9 kg MS ha-1 dia-1) do capim-annoni. Durante os 111 dias da fase vegetativa, a biomassa das plantas foi composta somente por folhas. O florescimento iniciou a partir do 132º dia após o corte. Aos 174 dias de crescimento, o capim-annoni acumulou cerca de 4.000 kg de MS ha-1, dos quais 650 kg MS ha-1 foi composta por inflorescências. A gramínea apresentou área foliar específica de 72 cm2 g-1 e índice de área foliar máximo de 2,1. A razão de área foliar reduziu de 72,2 para 43,9 cm2 g-1 entre o 23º e o 174º dia após o corte. A análise bromatológica mostrou elevados teores de fibra em detergente neutro (85,390,4%) e fibra em detergente ácido (39,4-42,8%), e baixo teor de proteína bruta (3,9-9,9%), indicando a baixa qualidade nutricional do capim-annoni.

ABSTRACT The objective of this work was to evaluate the dominance, growth and bromatology of tough lovegrass or 'annoni' grass (Eragrostis plana) in secondary vegetation area. The evaluations were carried out at 23, 45, 64, 86, 111, 132, 153, and 174 days of growth after a mowing. The tough lovegrass was the dominant species on the area, accounting for 76 to 90% of biomass. There was a linear increase for leaf (9.8 kg DM ha-1 day-1) and total dry mass (16.9 kg DM ha-1 day-1) of the tough lovegrass. During the 111 days of the vegetative stage, the biomass was composed only of leaves, and the flowering started at 132 days. At 174 days, the tough lovegrass accumulated about 4,000 kg DM ha-1, 650 kg DM ha-1 of which was composed of inflorescences. The growth analysis revealed a specific leaf area of 72 cm2 g-1 and a maximum leaf area index of 2.1. The leaf area ratio decreased from 72.2 to 43.9 cm2 g-1 between the 23rd and 174th days. The bromatological analysis showed a high content of neutral detergent fiber (85.3-90.4%) and acid detergent fiber (39.4-42.8%), as well as low crude protein content (3.9-9.9%), indicating the low forage quality of the species.

Este estudo teve como objetivo acessar a divergência genética em germoplasma de grama-missioneira-gigante (Axonopus jesuiticus x A. scoparius) com base em caracteres morfológicos e agronômicos. Cinco acessos foram avaliados no campo: V14337, V14403, V14404, V14405 e V14406. Três grupos contrastantes foram formados pelo método de agrupamento UPGMA: V14337 e V14404 formaram um grupo, V14403 e V14405 formaram outro, e V14406 ficou isolado dos demais acessos. Os caracteres morfológicos mais evidentes para identificar os acessos foram a altura da planta e a alteração da cor da folha. Somente o acesso V14406 apresentou folhas verde-púrpuras. Os outros quatro acessos diferiram quanto à altura da planta e produção de matéria seca, com superioridade dos acessos V14337 e V14404. A elevada similaridade, acessada pela distância euclidiana média, sugere que V14337 e V14404 compartilham o mesmo genótipo. A variabilidade genotípica entre os acessos indica seu uso potencial em programas de melhoramento genético.

This study had the objective of assessing the genetic divergence in giant missionary grass (Axonopus jesuiticus x A. scoparius) germplasm based on morphological and agronomic traits. Five accessions were evaluated in the field: V14337, V14403, V14404, V14405 and V14406. Three contrasting groups were formed using the UPGMA clustering method: V14337 and V14404 formed one group, V14403 and V14405 formed another, and V14406 was isolated from the other accessions. The most striking traits for the identification of the accessions were the height of the plant and the change color of the leaf. Only V14406 accession had purplish green leaves. The other four accessions differed with regards to plant height and dry matter production, with superiority of V14337 and V14404 accessions. The high similarity, as assessed by the mean Euclidean distance, suggests that V14337 and V14404 share the same genotype. The genotypic variability among accessions indicates their potential use in breeding programs.

This study evaluated the morphological development of two populations of tough lovegrass during 120 days of continuous growth (Experiment I), and the regrowth of one population under the combination of cutting height (5 cm and 10 cm) and phenological stage at the first cutting (vegetative and beginning of flowering; Experiment II). In Experiment I, plants were harvested at 30, 60, 90 and 120 days of growth; in Experiment II, three cuttings were carried out at every 30 days, and the plants were harvested four weeks after the previous one. In Experiment I, the populations did not differ for morphological development, showing a linear increase in height and tiller number, and a quadratic trend for root and shoot dry matter (DM). At 120 days of growth, plants presented 10 basal tillers and 80 leaves, strongly compressed at the base and no sign of senescence. In Experiment II, there was no significant cutting height × phenological stage interaction, but cuttings at 5 cm reduced plant size and yield. Cuttings started at the vegetative stage decreased the root (3.06 g DM/plant) and stubble dry matter (1.17 g DM/plant), compared with 6.84 g and 3.99 g DM/plant, respectively, with cuttings started at the flowering stage. Tough lovegrass shows basal architecture, basal bud renovation, leaves densely compressed in the tiller base, high belowground allocation, and elongation of internodes only in reproductive stage. Mechanical control is an alternative method to minimize its growth, especially if it is carried out early in the growing season and at low cutting height.

Este estudo foi realizado para investigar o efeito do extrato de folhas e raízes de capim-annoni-2 (Eragrostis plana) no crescimento de plântulas de trevo-branco (Trifolium repens), em dois experimentos. O primeiro experimento foi conduzido como teste-piloto, no qual foram testadas duas concentrações (30% e 60%) de extrato aquoso de folhas. No experimento II houve uma combinação de fonte (folhas e raízes) e concentração (5% e 10%) dos extratos. Água destilada foi utilizada como testemunha em ambos os ensaios. Cinqüenta plântulas com sete dias de idade foram colocadas em caixas gerbox, sobre papel-filtro umedecido com os extratos, e incubadas a 25ºC durante 14 dias. No primeiro experimento, o percentual de plântulas normais decresceu em 82,5% e 100% nas concentrações de 30% e 60%, respectivamente, o que indicou a necessidade de se aumentar a diluição dos extratos. No experimento subseqüente, os extratos das duas origens, a 10% de concentração, reduziram em 78% o percentual de plântulas normais e aumentaram o percentual de plântulas anormais, que atingiu 27%. A 5% o extrato de folha foi o tratamento mais deletério, resultando em maior mortalidade (M=27,6%) e anormalidade (A=19,5%) de plântulas, comparado ao de raiz (M=4,8%; A=9,5%) e à testemunha (M=2,4%; A=0,25%). As alterações morfológicas causadas pelos extratos foram necrose da radícula, retenção dos cotilédones e ausência de raízes secundárias. Os resultados sugerem que os compostos alelopáticos de folhas e raízes do capim-annoni-2 diferem quanto à natureza química e/ou concentração.

This study was carried out to investigate the effect of extracts of leaf and roots of tough lovegrass (Eragrostis plana) on seedling growth of white clover (Trifolium repens), in two experiments. The first experiment was conducted as a pilot test, in which two concentrations (30 and 60%) of leaf aqueous extract were tested. In Experiment II, source (leaf/root) and concentration (5 and 10%) of the extracts were combined. Distilled water was used as control in both trials. Fifty seedlings at 7 days of age were placed in gerbox containers on filter paper moistened with extracts and incubated at 25°C for 14 days. In the first experiment, percentage of normal seedlings decreased by 82.5% and 100% at the concentrations of 30% and 60%, respectively, which indicated the need to increase the dilution of the extracts. In the subsequent experiment, the extracts from the two sources, at 10% of concentration, reduced by 78% the percentage of normal seedling and increased the percentage of abnormal seedlings, which reached 27%. At 5% concentration, the leaf extract was the most deleterious treatment, resulting in greater mortality (M=27.6%) and abnormality (A=19.5%) of seedlings, compared to the root extract (M=4.8%; A=9.5%) and the control (M=2.4%; A=0.25%). The morphological changes caused by the extracts were radicle necrosis, retention of cotyledons and absence of secondary roots. The results suggest that allelopathic compounds from leaves and roots of tough lovegrass differ in chemical nature and/or concentration.