Características morfoanatômicas, nutricionais e produtividade de forrageiras tropicais submetidas ao sombreamento

• Ano de defesa: 2007
• Autor(a) principal: Gobbi, Kátia Fernanda
• Orientador(a): Garcia, Rasmo
• Banca de defesa: Paciullo, Domingos Sávio Campos , Queiroz, Domingos Sávio
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Brachiaria decumbens; Arachis pintoi; Sombreamento
• Palavras-chave em Inglês: Brachiaria decumbens; Arachis pintoi; Shading
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA
• Link de acesso: http://locus.ufv.br/handle/123456789/1677

Leaf anatomy, morphological characteristics and nutritive value of signalgrass (Brachiaria decumbens cv. Basilisk) and forage peanut (Arachis pintoi cv. Amarillo) were evaluated in response to three shade levels (0, 50 and 70%). The aim of this study was to determine the acclimation and yield capacity of these forage species under low light. Treatments were arranged in three replicates of a randomized complete block design. There were three and two harvests within the experimental period, for signalgrass and forage peanut, respectively. Grass and legume showed changes in leaf anatomy and morphological characteristics that affected its dry matter production and nutritive value under shade. In general, dry matter production of both species decreased (P<0.01) with shade. Shading promoted significant increase (P<0.05) of specific leaf area (SLA) of forage species, in all harvests evaluated. In signalgrass leaves, the SLA increase was followed by a linear reduction (P<0.05) in leaf thickness, under shade. On the other hand, forage peanut leaf thickness was not altered by shade, in spite of linear decrease (P<0.05) of palisade parenchyma thickness. Stomatal density was decreased linearly (P<0.05) on both leaf surfaces when forage peanut and signalgrass were grown under increased shade levels. The leaf blade cross-sectional area occupied by different tissues was not affected by treatments, with some exceptions in signalgrass leaves. Leaf area per leaflet and leaf area per tiller increased (P<0.05) with decreased light levels. Nevertheless, leaf area index (LAI) was not changed in studied species, except in the second harvest for forage peanut, where occurred linear decrease (P<0.05) of LAI with shading. In all harvests, average sward height, forage peanut petiole length, as well as signalgrass stem and leaf blade length were significantly increased (P<0.05) by shade. On the other hand, tiller population density in signalgrass sward decreased linearly (P<0.001) with shading, in the three harvests evaluated. Mean tiller weight was only affected in the third harvest, showing a linear increment (P<0.01) with increasing shading. In general, the proportion of leaves and stems, and consequently leaf:stem ratio were not altered (P>0.05) by treatments, in both species. Dry matter content of signalgrass and forage peanut decreased (P<0.05) with shade. Moreover, under shade, both species showed greater (P<0.05) crude protein content. In the two harvests of forage peanut, plants submitted to increased shade levels presented significant increment (P<0.05) in neutral detergent fiber (NDF) and acid detergent fiber (ADF) content. In the first harvest of signalgrass, shading did not promote significant alteration (P>0.05) in plant cell wall content, but in the second harvest it was observed linear reduction (P<0.05) in NDF and ADF content under shade. In the third harvest of grass, shading induced increment (P<0.05) only in ADF content. The variation in macronutrients concentration was not consistent between species and harvests, but in general, the concentrations were higher under shade. In spite of chemical alterations found under shade, the in vitro dry matter digestibility of signalgrass and forage peanut was not significantly affected (P>0,05) in any harvest. Anatomical and morphological changes observed in plants under shade indicate species acclimation and tolerance to low light conditions, but nutritive value of grass and legume was not expressively affected by shading. Signalgrass and forage peanut have great potential to produce quality forage in silvopastoral systems where light transmission level stay around 50% of photosynthetically active radiation.