Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Changes in stomatal function and water use efficiency in potato plants with altered sucrolytic activity.

Abstract: As water availability for agriculture decreases, breeding or engineering of crops with improved water use efficiency (WUE) will be necessary. As stomata are responsible for controlling gas exchange across the plant epidermis, metabolic processes influencing solute accumulation in guard cells are potential targets for engineering. In addition to its role as an osmoticum, sucrose breakdown may be required for synthesis of other osmotica or generation of the ATP needed for solute uptake. Thus, alterations in partitioning of sucrose between storage and breakdown may affect stomatal function. In agreement with this hypothesis, potato (Solanum tuberosum) plants expressing an antisense construct targeted against sucrose synthase 3 (SuSy3) exhibited decreased stomatal conductance, a slight reduction in CO(2) fixation and increased WUE. Conversely, plants with increased guard cell acid invertase activity caused by the introduction of the SUC2 gene from yeast had increased stomatal conductance, increased CO(2) fixation and decreased WUE. (14)CO(2) feeding experiments indicated that these effects cannot be attributed to alterations in photosynthetic capacity, and most likely reflect alterations in stomatal function. These results highlight the important role that sucrose breakdown may play in guard cell function and indicate the feasibility of manipulating plant WUE through engineering of guard cell sucrose metabolism.

Effects of Climatic Variability and Deforestation on Surface Water Regimes

Abstract: The river flow regime of the Amazon basin exhibits considerable variability at the interannual and interdecadal scales. A major source of variation is the El Nino–Southern Oscillation (ENSO) events. El Nino events cause a decrease in rainfall, river flow, and inundation patterns throughout the entire region, with the strongest reductions happening in the northern part of the basin. On the other hand, La Nina events cause increased river flow for the northern tributaries and the main stream, but apparently do not cause a discernible pattern of climate variability in the southern part of the basin. ENSO events are different one from the other. While most El Nino events cause reductions in precipitation and river flow over the entire area of northern Amazonia, some El Nino events change precipitation only over northwestern Amazonia. The strength of the ENSO events through the decades is modulated by an interdecadal signal possibly associated with the Pacific Decadal Oscillation. La Nina (rainy) events are rainier during the 1940s–1950s and 1970s, while El Nino (dry) events are drier during the 1960s and since the 1980s. It is also apparent that the interannual variability was damped during the 1930s–1960s. In addition to these modes of variability caused by varying rainfall patterns, in some regions where changes in land cover are extensive, changes in evapotranspiration may drive increases in river flow, increasing the runoff coefficient. This has been clearly documented for the Tocantins basin, and there is evidence that the Obidos runoff coefficient is also increasing.