Anatomical characteristics of forage species from the caatinga in different conditions in the northeastern semi-arid region

The knowledge of the anatomical characteristics of forage plants accounts for differences in digestibility of the forage, however there are few studies with the purpose of evaluating such characteristics in plants of the caatinga. The study was designed to assess the effect of the environment on three different semi-arid climate conditions on the proportion of leaf blade and petiole tissue of 'mani?oba' (Manihot glaziovii Muell.), 'moror?' (Bauhinia forficata Linn.) and 'feij?o bravo' (Capparis flexuosa Linn.). The plant material was collected in the three municipalities, during the month of June 2011 (rainy season), where we have selected five plants belonging to each species, of which was collected around the tops of the trees, leaves and petioles in vegetative stage for preparation of permanent slides. From the images obtained the total area measured (um) occupied by tissues and the participation (%) of the epidermis (EP), sclerenchyma (SC), xylem fibers more associated (XY), phloem (PH) and collenchyma (CO). The mesophyll region (ME) was calculated by the difference between the total cross-sectional area and the areas of other tissues, quantifying the number of vascular bundles. The experimental design used in the evaluation of the results was completely randomized design with five replications. The anatomical structures of the blades and petioles of the species evaluated presented specific features and with adaptive alterations different weather conditions. Differences were found (p < 0.05) in tissue proportion between the species and the climatic conditions of the regions were responsible for changes in anatomical order on all species. The highest proportions were observed in tissue 'moror?' with 18.06% (EP) in leaf blade and 12.13% (XY) and 18.82% (SC) in the petiole, 'mani?oba' with 16.61% (XY) and 2.16% (CO) on the leaf blade and 4.05% (CO) in the petiole and 'feij?o bravo' at 1.61% (PH), 10.14% (SC) and 66.84% (ME) on the leaf blade and 3.44% (EP), 9.55% (PH) and 66.46% (ME) in the petiole. The quantitative anatomic analysis of leaf blade suggests that Capparis flexuosa is the forage that presents the greatest potential for presenting qualitative higher proportion of high digestibility tissues in leaf blades and petioles.