Morfologia e anatomia foliar comparada de Buxus sempervirens L. e Buxus balearica Lam. oriundos de diversas regiões da Península Ibérica
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2015-09-17
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Buxus é um género exótico introduzido na Península Ibérica (PI) pelas dinâmicas glaciares. Caracterizado por arbustos de folha persistente, o género apresenta aspetos morfológicos peculiares e uma vasta gama ecológica, o que o torna economicamente importante. Existem apenas duas espécies de Buxus presentes na Europa, Buxus sempervirens e Buxus balearica. A primeira encontra-se distribuída pelo centro e sul da Europa, e em Portugal apresenta maior concentração em Trás-os-Montes, nos vales do Rio Sabor e Tua. Por sua vez, B. balearica mostra uma distribuição limitada às Ilhas Baleares e ao sul de Espanha. No presente estudo pretendeu-se caracterizar e estabelecer aspetos que contribuam para a distinção das duas espécies, e determinar variações dentro da mesma espécie em resultado de adaptações às condições edafo-climáticas das regiões. Foi realizado um estudo morfo-anatómico em amostras foliares de exemplares respetivos a 18 populações de Buxus, oriundos da Península Ibérica: 6 populações de B. balearica, 6 de B. sempervirens do Sistema Cantábrico (SC) e 6 de B. sempervirens do Sistema Ibérico (Ib). Este estudo incluiu a análise da anatomia foliar e de aspetos morfo-anatómicos relacionados com a economia da água nas folhas. Verificou-se que as espécies apresentam diferenças morfo-anatómicas. A espécie B. balearica apresenta área foliar e massa por unidade de área da superfície foliar (LMA) superiores, ao passo que B. sempervirens possui menores folhas com menor espessura foliar e menor LMA. Ambas as espécies possuem folhas dorsiventrais e hipoestomáticas, embora B. balearica apresente maior densidade de estomas. Apresentam também características xeromórficas, indicando estar adaptadas à secura. As populações de B. sempervirens do Sistema Ibérico parecem adotar mecanismos de resistência ao clima Mediterrânico, tais como maior espessura da folha, do parênquima clorofilino em paliçada e da cutícula, bem como LMA e densidade estomática superiores. Pela análise canónica discriminante, a espessura da cutícula superior foi a variável principal na discriminação de todas as populações de Buxus. As variações morfo-anatómicas entre as várias populações estudadas podem ser o resultado das variações regionais no ambiente, tais como a fertilidade do solo, sazonalidade térmica e/ou diferenças filogenéticas.
Buxus is an exotic genus introduced in the Iberian Peninsula by glacial dynamics. This genus is characterized by evergreen shrubs having some distinctive features and a wide range of ecological characteristics, which makes it economically important. There are only two species of Buxus in Europe, Buxus sempervirens and Buxus balearica. The first one is extensively distributed along Central Europe, and in Portugal it is found in Trás-os-Montes in the valley of Sabor River and Tua. In turn, B. balearica has a distribution limited to the Balearean Island and south of Spain. The objective of the present study was to characterize and establish relevant aspects that contribute to the distinction of the two species, and to determine the variations within the same species related to the adaptation to the environmental conditions of the regions. A morpho-anatomical study was carried out using samples of leaves from 18 populations of Buxus, gathered in the Iberian Peninsula: 6 populations of B. balearica, 6 of B. sempervirens from the Cantabrian System and 6 of B. sempervirens from the Iberian System. This study included the leaf anatomical analysis and morpho-anatomical aspects related to the way the leaves avoid dehydration. The obtained results indicate morpho-anatomical differences between the species. B. balearica has bigger foliar area and higher leaf mass per unit area (LMA) than B. sempervirens that has smaller and thinner leaves, with lower LMA. Both species contain dorsiventral and hypostomatic leaves, although B. balearica presents higher stomatal density. Moreover, these two species present xeromorphic features that indicate good adaptation to drought. The population of the Iberian System of B. sempervirens revealed mechanisms of resistance to the Mediterranean climate such as thicker leaves, in consequence of thicker palisade parenchyma and cuticle, as well as higher LMA and higher stomatal density. The discriminant canonical analysis shows that the upper cuticle thickness was the principal morpho-anatomical variable for the discrimination of all the populations of Buxus. The morpho-anatomical variations from all the studied populations can be the result of the regional variations of the environment, such as the soil fertility, thermal seasonality and/or phylogenetic differences.
Buxus is an exotic genus introduced in the Iberian Peninsula by glacial dynamics. This genus is characterized by evergreen shrubs having some distinctive features and a wide range of ecological characteristics, which makes it economically important. There are only two species of Buxus in Europe, Buxus sempervirens and Buxus balearica. The first one is extensively distributed along Central Europe, and in Portugal it is found in Trás-os-Montes in the valley of Sabor River and Tua. In turn, B. balearica has a distribution limited to the Balearean Island and south of Spain. The objective of the present study was to characterize and establish relevant aspects that contribute to the distinction of the two species, and to determine the variations within the same species related to the adaptation to the environmental conditions of the regions. A morpho-anatomical study was carried out using samples of leaves from 18 populations of Buxus, gathered in the Iberian Peninsula: 6 populations of B. balearica, 6 of B. sempervirens from the Cantabrian System and 6 of B. sempervirens from the Iberian System. This study included the leaf anatomical analysis and morpho-anatomical aspects related to the way the leaves avoid dehydration. The obtained results indicate morpho-anatomical differences between the species. B. balearica has bigger foliar area and higher leaf mass per unit area (LMA) than B. sempervirens that has smaller and thinner leaves, with lower LMA. Both species contain dorsiventral and hypostomatic leaves, although B. balearica presents higher stomatal density. Moreover, these two species present xeromorphic features that indicate good adaptation to drought. The population of the Iberian System of B. sempervirens revealed mechanisms of resistance to the Mediterranean climate such as thicker leaves, in consequence of thicker palisade parenchyma and cuticle, as well as higher LMA and higher stomatal density. The discriminant canonical analysis shows that the upper cuticle thickness was the principal morpho-anatomical variable for the discrimination of all the populations of Buxus. The morpho-anatomical variations from all the studied populations can be the result of the regional variations of the environment, such as the soil fertility, thermal seasonality and/or phylogenetic differences.
Descrição
Dissertação de Mestrado em Engenharia do Ambiente
Palavras-chave
Buxus balearica , Península Ibérica , Buxus sempervirens , Anatomia foliar , Morfologia foliar , Ecologia funcional