Drought is one of the main environmental constraints that can reduce plant yield. Nitric oxide (NO) is a signal molecule involved in plant responses to several environmental stresses. The objective of this study was to investigate the cytoprotective effect of a single foliar application of 0, 1, 10 or 100 µM of the NO donor sodium nitroprusside (SNP) in sunflower plants under water stress. Water stressed plants treated with 1μM SNP showed an increase in the relative water content compared with 0 μM SNP. Drought reduced the shoot dry weight but SNP applications did not result in alleviation of drought effects. Neither drought nor water stress plus SNP applications altered the content of photosynthetic pigments. Stomatal conductance was reduced by drought and this reduction was accompanied by a significant reduction in intercellular CO 2 concentration and photosynthesis. Treatment with SNP did not reverse the effect of drought on the gas exchange characteristics. Drought increased the level of malondialdehyde (MDA) and proline and reduced pirogalol peroxidase (PG-POD) activity, but did not affect the activity of superoxide dismutase (SOD). When the water stressed plants were treated with 10 μM SNP, the activity of PG-POD and the content of proline were increased and the level of MDA was decreased. The results show that the adverse effects of water stress on sunflower plants are dependent on the external NO concentration. The action of NO may be explained by its ability to increase the levels of antioxidant compounds and the activity of ROS-scavenging enzymes.

Abstract:The Pantanal wetlands represent one of the largest flood plains in the World, with extreme climatic variations between dry and wet seasons. The area shelters a high diversity of habitats, representing the main formations found in this sub-region: grasslands, savannah, forested savannah, riparian forests, bays and salines, and Negro river itself. This habitat variability determines the structure and dynamics of the bird community, because most species are closely related to specific habitats. For this, we studied the abundance of bird species from 2001 to 2004 in a Pantanal area of Fazenda Rio Negro, Aquidauana, Brazil. The abundance was compared among those four consecutive years, seasons (dry and wet), time of the day (morning and afternoon), and also between seven different habitats, in order to determine the variation in distribution patterns and habitats used by birds. For this, we used the linear transect method in each of the seven habitats, and recorded bird abundances to obtain richness. The richness registered in the mosaic of habitats was of 201 species for the savannah, 87 in forested savannah, 116 in the riparian forest, 75 in grasslands, 120 in bays, 92 in the salines and 64 in the Negro river, accounting for 348 species in the Pantanal of Rio Negro. Overall, 98 species of migratory birds were registered. The results highlighted some important issues regarding the total abundance of birds in Nhecolândia: Psittacidae was the most abundant family in the region, with prominence in all environments. Recurvirostridae, a monospecific family, showed expressive abundance due to the dominance of Himantopus mexicanus in the salinas, followed by Ardeidae, Anatidae and Cracidae. Other families with high abundance were Tyrannidae, Columbidae, Thraupidae and Emberizidae, all in predominantly terrestrial environments. Moreover: a) The highest number of specimens was recorded in the morning period and in the dry season, regardless of the habitat; b) there were no differences in abundance in the same habitat along the years, but the abundance was different among habitats. In general, the results indicated that there is a relatively stable bird population in each habitat along the annual cycle, but there were differences in abundance among habitats. Thus, additional studies on food availability in dry and wet seasons should be better explored in the future, either in this region or in other Pantanal regions. This fact could better explain the seasonal dynamics of the richness and abundance of birds in the Pantanal area in general. Rev. Biol. Trop. 65 (4): 1358-1380. Epub 2017 December 01.Key words: pantanal, bird community, mosaic of habitats, Mato Grosso do Sul. The Pantanal wetlands stand out for being one of the largest flood plain in the world, in which extreme climatic variations occur between dry (April to September) and wet seasons (October to March). During the wet season, large areas are flooded (Por, 1995). In the sub-region of Nhecolândia, the terrain, together with the rainfall conditions, is con...

Geographical variation of bird vocalizations may be related to factors influencing sound production and sound propagation. If birds, e.g. the Great Antshrike (Taraba major), produce vocalizations that develop normally in the absence of learning, these variations may reflect evolutionary divergence within species. In this case, vocal variation could be influenced by habitat structure, since abiotic features and vegetal cover affect sound propagation through environment. Selective pressures may be acting on populations in different ways, which could culminate in a process of speciation. Thus, we searched for structural variation of Great Antshrike vocalizations between subspecies and sought for relationships between these vocal variation and environmental structure. We found variations in frequency and time features of vocalizations among subspecies, which are correlated to latitude, elevation and climate. We also observed an increase in vocal differences along with an increase in distances between individuals, which could reflect isolation of subspecies and the vocal adaptation to different environments. ARTICLE HISTORY

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Variation in the avian vocal signals emitted may have a significant impact on species evolution. Vocal divergence in suboscine species like Giant Antshrike (Batara cinerea) may be associated with selective adaptation, since learning has little influence on vocal development and variation in acoustic structure cannot be attributed to learning deviation. Consequently, tracheophone suboscine species are ideal subjects to explore vocal variation, since cultural evolution does not seem to influence vocal variation in this group. Environmental conditions may determine the selection of vocal features because acoustic transmission could be attenuated under certain conditions of temperature, humidity and vegetation cover. Here, we examined vocalizations of Giant Antshrike and assessed possible acoustic variations between two disjunct groups (Andean and Atlantic), correlating the differences to the environmental structure. Univariate and multivariate analysis show temporal and spectral differences between both groups. Andean individuals produce vocalizations with longer duration, faster trill rates, shorter syllable duration and higher frequencies. Environmental features are different between the two populations, and they are correlated to the acoustic structure of vocalizations. Temporal variations arise directly from climatic influence, while spectral divergence could be a secondary effect of morphological adaptation to habitat structure.