Showing papers by "Marco Antonio Oliva published in 2005"

Micromorphological and anatomical alterations caused by simulated acid rain in restinga plants: eugenia uniflora and clusia hilariana

Abstract: Eugenia uniflora and Clusia hilariana seedlings were submitted to simulated acid rain, pH 3, for 40 days. The degree of visible injury and the anatomical and micromorphological alterations were determined 24 hours after the last simulation. E. uniflora presented a higher degree of leaf necrosis. The adaxial epidermis and part of the palisade parenchyma of the entire leaf blade were affected and hypertrophy, hyperplasia and cicatrization tissue differentiation occurred. Erosion and morphological modification of the epicuticular wax and alterations in the epidermis were detected on the upper and lower leaf surfaces. Stomata with deformed ostioles and rupture of the stomatal ledge were observed. C. hilariana presented necrosis in leaf margin and in abaxial leaf surface, showing collapsed cells or with plasmolized aspect, cicatrization tissue, epicuticular wax alterations, occasional leaf perforations, irregular arrangement of adaxial epidermis cells and twisted subsidiary cells. The structural alterations indicated a greater susceptibility of E. uniflora to acid rain. he lower sensibility of C. hilariana can be related with the anatomical characteristics as: thick cuticle with evident cuticular flanges, three layers of hypodermis and mesophyll more thick and compact.

Gramíneas bioindicadoras da presença de flúor em regiões tropicais

Abstract: Ten species of tropical grasses, Andropogon gayanus Kunth cv. Planaltina, Panicum maximum Jacq. cv. Coloniao, Panicum maximum Jacq. cv. Tobiata, Chloris gayana Kunth, Eragrostis curvula (Schrad.) Nees, Paspalum notatum Flug. cv. Pensacola, Hiparrhenia rufa (Nees) Stapf., Melinis minutiflora Pal. de Beauv., Brachiaria decumbens Stapf., Brachiaria humidicola (Rendle) Schw. and Lolium multiflorum ssp. italicum var. lema were treated with simulated rain containing 5, 10, and 15 g.m-3 of fluoride, in order to evaluate their relative sensitivity and potential as bioindicator for fluoride under tropical conditions. The plants were cultivated according to standardized techniques for active bioindication. The development of visible damages, the accumulation and distribution of fluoride and the dry weight yield were used to assess the effects of the element on the plants. All studied species showed distinct pattern of fluoride accumulation, fluorine contents above the accepted toxic levels for sensitive species (30 µg.g-1) and a good correlation between fluoride content and the phytotoxicity index, except for Brachiaria humidicola. Chloris gayana and Panicum maximum cv. Coloniao were the species that better adapted to the standardized cultivation techniques, based on their growth rates, sprout homogeneity and fast appearance of visible symptoms (chlorosis and necrosis). Fluoride effects on stomatal conductance, CO2 assimilation and dry weight yield were also evaluated in these two species, with potential for bioindication use. The results indicate Panicum maximum cv Coloniao as a responsive bioindicator while Chloris gayana as a tolerant species, similarly to L. multiflorum.

Effects of simulated acid rain on the growth of five Brazilian tree species and anatomy of the most sensitive species (Joannesia princeps)

Abstract: Seedlings and young saplings of some woody species were exposed to simulated low-pH acid rain, in order to develop a response screening for tropical tree species by determination of the symptoms of foliar injury and growth responses, as well as to identify anatomical alterations in the leaf blade of the most sensitive species. Gallesia integrifolia (Spreng.) Harms, Genipa americana L., Joannesia princeps Vell., Mimosa artemisiana Heringer & Paula and Spondias dulcis Forst.f. were exposed daily to 20 min of acid rain, pH 3.0, for 10 consecutive days. The degree of leaf damage and the anatomical alterations observed were efficient parameters to determine the sensitivity to acid rain. At the end of the experiment J. princeps was the most sensitive species as determined by foliar injury and seedling growth. The degree of leaf damage was similar among the seedlings, except in S. dulcis, which showed reduced percentage of foliar injury. Necrotic and chlorotic spots on the leaf blade occurred. In the most sensitive species, J. princeps, necrotic blade tissues showed accumulation of phenolic compounds, hypertrophy and collapsed cells. Most of the structural alterations were observed in the adaxial epidermis, the palisade parenchyma and spongy parenchyma and the abaxial epidermis. Long-term experiments with seedlings of S. dulcis and saplings of G. integrifolia are suggested, to characterise the response of these species that presented fewer symptoms but whose growth was affected under acid rain.

Capacidade de cultivares de arroz de modificar o pH de soluções nutritivas na presença de alumínio

Abstract: The objective of this work was to evaluate aluminum effect on the ability of two rice cultivars, Fernandes (tolerant) and Maravilha (sensitive), to change the pH of nutrient solutions with different NO3-/NH4+ ratios. After plant exposure to 0 mM and 1.5 mM Al for 15 days, the amount of exudated protons, elongation, dry matter yield and Al content of roots and leaves were determined. Elongation and dry matter yield of roots and leaves reduced in the presence of Al independently of NO3-/NH4+ ratio, and this reduction was intensified with increasing of NH4+ concentration. Aluminum contents increased in roots and leaves with increasing of NH4+ concentration in nutrient solution. An alkalization of the nutrient solution containing N exclusively in NO3- form was observed, but this alkalization decreased with Al treatment. In nutrient solutions containing NH4+, on the contrary, an acidification was observed, which intensified with the increase of NH4+ concentration. The tolerant cultivar always consumed more protons of the nutrient solution containing N exclusively in the NO3- form and less protons of that containing NH4+, independently of the NO3-/NH4+ ratio. This cultivar, therefore, showed higher ability to adjust its protons balance, changing the pH to values that favored lower Al uptake and higher tolerance to aluminum.