Anatomia foliar de Brachiaria spp. em diferentes idades de rebrota associada com a qualidade da forragem

Abstract

The present work intended to verify whether there is an effect upon the regrowth age of different genotypes in the leaf anatomy of Brachiaria spp., and how that can affect its quality as a forage plant. Leaf tissues of the genotypes of Brachiaria brizantha (Hochst.) Stapf. (cv Marandu), Brachiaria decumbens Stapf. Prain. (cv. Basilisk), Brachiaria ruziziensis (R. Germ & Evrad) (cv. Kennedy) and of three clones (1, 95 and 97) of Brachiaria ruziziensis were evaluated. Those plants were cultivated under ideal conditions recommended for the cultivation of Brachiaria. At first, the leaves were collected at three regrowth ages to determine which would be the ideal age; afterwards, with the ideal age determined, the genotypes within the ideal age were compared. By making use of the usual microtechnique, sections free hand were done and semipermanent slides were manufactured. Photomicrographs and proportions of the tissues in the interveinal region and of the midrib were done utilizing the image software Image J. for the determination of the regrowth age the design was completely randomized with three treatments and nine replications and to compare the genotypes the design was completely randomized with six treatments and six replications. The statistical analyses were conducted on software Sisvar and the means compared by the Scott-Knott te st. Over time, at 8 days of regrowth the tissues already presented differentiation, but they did not present full expansion as observed at 15 days, this process lasted till the 29 days’ regrowth, however at that date, increased deposition of lignified tissues occurred. In most of the genotypes evaluated, smaller amount of fibers was observed at 15 days as compared with the 29 days’ regrowth. In addition, one can observe at 15 days increased amount of parenchyma in relation to the 8 days of regrowth. With the ideal age of 15 days of regrowth set, the genotypes were compared and it was found that Clone 1 of B. ruziziensis presented greatest proportion of parenchyma and smallest proportions of lignified tissues like of vascular bundles and xylem. The same behavior was observed in B. decumbens. One can state that the regrowth age modifies the percentage of tissues in Brachiaria sp brining about increase of fibers and vascular bundles at 29 days of regrowth and that anatomical leaf structure is different among the genotypes evaluated, among them, B. decumbens and the Clone 1 of B. ruziziensis possess tissues with greatest digestibility potential.