Abstract
A macrófita aquática Salvinia auriculata Aubl. ocorre em diferentes regiões do Rio Capibaribe, no estado de Pernambuco, Brasil. Esse rio desemboca no mar e, consequentemente, apresenta setores com diferentes gradientes de salinidade. Este trabalho avaliou a fotossíntese, o crescimento e o teor de pigmentos fotossintetizantes de S. auriculata frente a um gradiente de salinidade. As plantas foram obtidas em um reservatório no município de Paudalho e foram levadas à casa de vegetação, onde foram mantidas em frascos de vidro contendo 250 mL de volume preenchido, posicionados em bancadas durante 40 h nas seguintes condições de salinidade: 0, 17 e 34, obtidas com água doce, mistura de água doce e salgada e água salgada, respectivamente. Ao final, as folhas das plantas tratadas com água salgada apresentaram mudança na coloração (de verde para marrom) e também as plantas tiveram redução no seu crescimento. A salinidade e o tempo afetaram negativamente as respostas fotossintetizantes das plantas, com diminuição de Fv/Fm, ETRmax e ETR conforme aumentava o conteúdo de sais ao qual as plantas estiveram expostas. Os padrões de respostas obtidos ajudaram a esclarecer a distribuição de S. auriculata, podendo ser regulada pela salinidade.
Highlights
Macrophyte assemblages are important ecological constituents of aquatic limnetic systems, where they are the main primary producers in these environments (ESTEVES, 1998)
The decrease in photosynthesis and growth rate under highest salinity can help to explain the reasons why the species does not occur in high saline waters, but some tolerance to intermediate values was detected
Non-halophytic macrophytes can show a decline in growth when subjected to a high salinity (WARWICK; BAILEY, 1997)
Summary
Macrophyte assemblages are important ecological constituents of aquatic limnetic systems (lotic or lentic ones), where they are the main primary producers in these environments (ESTEVES, 1998). Salvinia spp. are free-floating freshwater macrophytes that show an explosive growth rate under favorable conditions (GARDNER; AL-HAMDANI, 1997), such as nutrient enrichment caused by human activities (BINI et al, 1999) and high concentrations of NH4+ and NO3− (JAMPEETONG; BRIX, 2009a) This explosive growth can bring about negative consequences to aquatic ecosystems (ESTEVES, 1998). The plants can occupy wetlands and lagoons with moderately saline waters and close to coasts (GOMES et al, 2011), with possible biomass variation regulated by season (KUFNER et al, 2011) This species is reported to occur in different sections of the Capibaribe River, showing large biomass in certain areas (XAVIER, 2014). We evaluated the effects of seawater on photosynthetic activity and water content of the floating macrophyte S. auriculata, collected in a Capibaribe River reservoir, contributing to our understanding of the of distribution and abundance patterns of this species in coastal regions
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