Setaria parviflora (Poir.) Kerguélen and Paspalum urvillei Steudel are grasses that grow naturally in a soil with high iron contents. This study aimed to characterize morphoanatomically and histochemically the iron phytotoxicity on leaves and evaluate the phytoextraction potential of these grasses. Saplings were cultivated in hydroponic solution with and without excess Fe-EDTA. Regarding measurements taken on leaves, reduction was observed among treatments of Fe-EDTA on height values of abaxial epidermis and bundle sheath in both species. As for iron histolocalization, stronger reaction was observed in leaves of S. parviflora, in comparison with P. urvillei. Anatomical damage, such as protoplast retraction, irregular xylem, changes in cell volume, and cell collapse, and visual symptoms, like leaf bronzing, chlorosis, and necrosis, were similar in both species when exposed to excess iron; however, P. urvillei showed more severe damage. This species accumulated more iron in shoots than S. parviflora and therefore is more favorable for use in phytoextraction. The root system of both species accumulated higher iron concentrations in relation to shoots.

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Comanthera elegans (Bong.) L.R. Parra & Giul (''sempre-viva-pé-de-ouro'') is one of the most economically important species among the Eriocaulaceae in Brazil. Its inflorescences are used to make handicrafts and have long been exported to all over the world. The collection period usually begins in the second half of April and extends to May, occasionally until the first half of June. We assessed seed production and germinability throughout the 2006 harvest season: April-November, as well as the variation in morphology and anatomy of inflorescences along this period. In the evaluated flowering, seeds still had not yet been completely formed by early April, the onset month of commercial collection. Instead, germinable seeds were first observed in May, while seed dispersal was already in progress in early June. Collection in June resulted in plant uprooting, due to the tighter attachment of the scape to the rosette. The beginning and peak of germination occurred earlier for seeds from the most delayed collections, and the highest germinability was presented by seeds collected in September.We showed that the best period for the plant sexual reproduction surpasses the best period for commercial collection. Due to the onset of germinable seeds only as late as at the second half of the harvesting period, encouraging the delayed beginning of inflorescence collection may well represent a management strategy. Furthermore, the reservation of non-harvesting areas, which would secure the maintenance of plant populations in the wild and thus guarantee seed production and dispersal; maintaining remnants of inflorescences in collected areas; and encouraging cultivation should be considered.

We investigated the morphological and anatomical effects of simulated acid rain on leaves of two species native to the Brazilian Atlantic Rainforest: Paubrasilia echinata and Libidibia ferrea var. leiostachya. Saplings were subjected to acid rain in a simulation chamber during 10 days for 15 min daily, using HSO solution pH 3.0 and, in the control, deionized water. At the end of the experiment, fragments from young and expanding leaves were anatomically analyzed. Although L. ferrea var. leiostachya leaves are more hydrophobic, rain droplets remained in contact with them for a longer time, as in the hydrophilic P. echinata leaves, droplets coalesce and rapidly run off. Visual symptomatology consisted in interveinal and marginal necrotic dots. Microscopic damage found included epicuticular wax flaking, turgor loss and epidermal cell shape alteration, hypertrophy of parenchymatous cells, and epidermal and mesophyll cell collapse. Formation of a wound tissue was observed in P. echinata, and it isolated the necrosis to the adaxial leaf surface. Acid rain increased thickness of all leaf tissues except spongy parenchyma in young leaves of L. ferrea var. leiostachya, and such thickness was maintained throughout leaf expansion. To our knowledge, this is the first report of acidity causing increase in leaf tissue thickness. This could represent the beginning of cell hypertrophy, which was seen in visually affected leaf regions. Paubrasilia echinata was more sensitive, showing earlier symptoms, but the anatomical damage in L. ferrea var. leiostachya was more severe, probably due to the higher time of contact with acid solution in this species.

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