ABSTRACT
This study aimed to evaluate the existence of leaf anatomic characteristics in Tabebuia alba changed by air pollutants, which could be used as tool for a bioindication program. The quantification of mutagenic events on pollen grains also were measured. For this, median leaves and pre-anthesis flowers were collected from the adult plants from three places of Curitiba and one place in Araucaria, all nearby to the air monitoring stations. The comparison of the four study sites showed a reduction in leaf area, an increasing of stomatal density, subepidermic layer, epidermis in both faces and the amount of micronucleus. Also, there was reduction of chlorophyllian parenchymas at the site where there was the higher average for the ozone level. It was concluded that these modifications might be a consequence of the effect of troposferic pollution on T. alba plants. However, further studies with this species would be necessary to confirm its potential for bioindication.
ABSTRACT
The epiphytic fern Microgramma squamulosa occurs in the Neotropics and shows dimorphic sterile and fertile leaves. The present study aimed to describe and compare qualitatively and quantitatively macroscopic and microscopic structural characteristics of the dimorphic leaves of M. squamulosa, to point more precisely those characteristics which may contribute to epiphytic adaptations. In June 2009, six isolated host trees covered by M squamulosa were selected close to the edge of a semi-deciduous seasonal forest fragment in the municipality of Novo Hamburgo, State of Rio Grande do Sul, Brazil. Macroscopic and microscopic analyzes were performed from 192 samples for each leaf type, and permanent and semi-permanent slides were prepared. Sections were observed under light microscopy using image capture software to produce illustrations and scales, as well as to perform quantitative analyses. Fertile and sterile leaves had no qualitative structural differences, being hypostomatous and presenting uniseriate epidermis, homogeneous chlorenchyma, amphicribal vascular bundle, and hypodermis. The presence of hypodermal tissue and the occurrence of stomata at the abaxial face are typical characteristics ofxeromorphic leaves. Sterile leaves showed significantly larger areas (14.80cm2), higher sclerophylly index (0.13g/cm2) and higher stomatal density (27.75stomata/mm2) than fertile leaves. The higher sclerophylly index and the higher stomatal density observed in sterile leaves are features that make these leaves more xeromorphic, enhancing their efficiency to deal with limited water availability in the epiphytic environment, compared to fertile leaves.