Mirko Balestri

Arsenic-induced morphogenic response in roots of arsenic hyperaccumulator fern Pteris vittata

On the assumption that arsenic induces stress morphogenetic responses involved in As tolerance and hyperaccumulation in the Pteris vittata fern, we analyzed the root system of young sporophytes grown in 250, 334, and 500 μM As for five days and for 14 days. Anatomical and histological analyses were performed in plants grown for five days to evaluate the number, position, length and differentiation pattern of root hairs. AgNOR staining, employed to study nucleolus behavior in root apices, showed that arsenic influences nucleolar activity (evaluated by nucleolus size, number and absorbance) in the root meristem. In plants treated with 250 and 334 μM As an acropetal shift of root hair development and an increase in hair length and density were observed, linked to an ectopic pattern of differentiation. The opposite trend was recorded in plants treated with 500 μM As. It is worth noting the presence of living border-like cells, not yet observed in ferns, and their increase following As treatments. Analysis and vitality of border-like cells were surveyed after 14 days of treatments. In conclusion As treatments elicited a stress-induced morphogenic response which, by modifying the differentiation pattern, number and length of root hairs, modulating nucleolar activity and interacting with the rhizosphere by inducing border-like cell production, may adjust the rate of root uptake and its metabolic activity.

Morpho-functional adaptations in Cakile maritima Scop. subsp. maritima: comparation of two different morphological types.

Along the Italian maritime foredunes there are two different morphotypes of Cakile maritima Scop. subsp. maritima differing in leaf shape: one type is characterized by entire lamina, while the other one shows pinnatifi d leaves. Therefore, this study was performed to analyze leaf morpho-functional characters of both C. maritima morphotypes in order to highlight the peculiar adaptations to the ecological conditions of sand dune environments and to compare the two different morphological types. The morpho-functional traits analyzed are leaf roll, general morphology of epidermis, vesicular cells, salt crys- tals, stomatal apparatus, stomatal density (SD), hydathodes, mesophyll, idioblasts, specifi c leaf area (SLA) and leaf dry matter content (LDMC). The most interesting anatomical adaptations to sand dune habitats are thick epidermal cuticle; high stomatal density; epidermal vesicular cells involved in water storage, sunlight refl exion and together with hydathodes in salt elimination; high development of palisade and water storage parenchyma; bundle sheath typical of C 4 leaf anatomy. Differences in several leaf characters between the two morphotypes seem to suggest that pinnatifi d morphotype is more resistant to stress and environmental disturbance than the entire type. The analysis of C. maritima distribution in two different coastal traits affected by progradation or erosional processes confi rmed this hypothesis.

Leaf anatomical adaptations of Calystegia soldanella, Euphorbia paralias and Otanthus maritimus to the ecological conditions of coastal sand dune systems

Abstract The aim of the present work is to characterize leaf morpho-functional adaptations of three pioneer sand dune plants - Calystegia soldanella, Euphorbia paralias and Otanthus maritimus - that are distributed on the foredunes where environmental stresses are stronger.The most interesting morpho-anatomical adaptations of the three psammophytes to the ecological conditions of coastal sand dune systems seem to be leaf orientation, leaf roll, non-glandular and glandular trichomes, general morphology of epidermis, morphology and localization of stomata, hydathodes, aerenchyma and water-storage parenchyma. Some of these characters may be proposed as “hard traits” in Plant Functional Type studies.