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Dalmagro H.J.,Programa de Pos Graduacao em Fisica Ambiental | Dalmagro H.J.,Institute Biologia | de Lobo F.A.,Programa de Pos Graduacao em Fisica Ambiental | de Lobo F.A.,Institute Biologia | And 9 more authors.
Photosynthetica | Year: 2013

The Pantanal is the largest wetland in the world with extremely high plant and animal diversity, but large areas have been invaded by Vochysia divergens Pohl (Vochysiaceae), a tree that is native to the Amazon Basin, and Curatella americana L. (Dilleniaceae), a tree that is native to the Brazilian savanna (cerrado). V. divergens is reportedly floodadapted, thus its ability to invade the Pantanal may not be surprising, but the invasion of C. americana is counterintuitive, because this species is adapted to the well-drained soils of the cerrado. Thus, we were interested in comparing the photosynthetic capacity, in terms of CO2 conductance, carboxylation, and electron transport of these species over a seasonal flooding cycle. Given that V. divergens is reportedly flood-adapted, we predicted that this species would have a higher photosynthetic capacity than C. americana, especially under flooding. To test this hypothesis we measured the photosynthetic CO2 response (PN/Cc) of V. divergens and C. americana within 1 year to determine, if photosynthetic capacity varied systematically over time and between species. Contrary to our hypothesis, V. divergens did not always have a higher photosynthetic capacity than C. americana. Rather, species differences were influenced by temporal variations in flooding and the leaf age. Leaf CO2 assimilation and photosynthetic capacity of both species were lower during the flood period, but the differences were not statistically significant. The physiological performance of both species was strongly related to leaf N and P concentrations, but P limitation appeared to be more important than N limitation for these species and ecosystem. Photosynthetic capacity was higher and more stable for V. divergens, but such an advantage did not result in a statistically significant increase in PN. Our results suggest that both species are tolerant to flooding even though they are adapted to very different hydrological conditions. Such physiological plasticity, especially for C. americana, might be a key feature for the ability to survive and persist in the seasonally flooded Pantanal. © 2013 Springer Science+Business Media Dordrecht.


Lobo F.A.,FAMEV UFMT | de Barros M.P.,Programa de Pos Graduacao em Fisica Ambiental | Dalmagro H.J.,Programa de Pos Graduacao em Fisica Ambiental | Dalmolin A.C.,Programa de Pos Graduacao em Fisica Ambiental | And 4 more authors.
Photosynthetica | Year: 2013

In this study, we presented the most commonly employed net photosynthetic light-response curves (P N/I curves) fitted by the Solver function of Microsoft Excel. Excel is attractive not only due to its wide availability as a part of the Microsoft Office suite but also due to the increased level of familiarity of undergraduate students with this tool as opposed to other statistical packages. In this study, we explored the use of Excel as a didactic tool which was built upon a previously published paper presenting an Excel Solver tool for calculation of a net photosynthetic/chloroplastic CO2-response curve. Using the Excel spreadsheets accompanying this paper, researchers and students can quickly and easily choose the best fitted P N/I curve, selecting it by the minimal value of the sum of the squares of the errors. We also criticized the misuse of the asymptotic estimate of the maximum gross photosynthetic rate, the light saturation point estimated at a specific percentile of maximum net photosynthetic rate, and the quantum yield at zero photosynthetic photon flux density and we proposed the replacement of these variables by others more directly linked to plant ecophysiology. © 2013 Springer Science+Business Media Dordrecht.


Dalmagro H.J.,Programa de Pos Graduacao em Fisica Ambiental | Lobo F.A.,Programa de Pos Graduacao em Fisica Ambiental | Vourlitis G.L.,California State University, San Marcos | Dalmolin A.C.,Programa de Pos Graduacao em Fisica Ambiental | And 3 more authors.
Photosynthetica | Year: 2014

Tropical savanna ecosystems are extremely diverse and important for global carbon storage. In the state of Mato Grosso, tropical savanna (locally known as the Cerrado), turns from well-drained, upland areas into seasonally flooded areas within the Pantanal; however, the Cerrado and the Pantanal share many common tree species, such as Vochysia divergens, a flood-adapted tree native to the Amazon Basin, and Curatella americana, a tree, adapted native to the welldrained the Cerrado. We measured the photosynthetic light response of these species in the the Cerrado and the Pantanal over a 1-year period to determine how these species physiologically adjust to these hydrologically distinct habitats. We hypothesized that neither species would experience a significant decline in maximum, light-saturated photosynthetic rate (Pmax) in their naturalized habitat. Physiological performance of each species was generally higher in the habitat that they were adapted to; however, our data indicated that both species have broad tolerance for seasonal variations in hydrology, allowing them to tolerate seasonal drought during the dry season in the Cerrado, and seasonal flooding during the wet season in the Pantanal. In V. divergens, flexible water-use efficiency, higher specific leaf area (SLA), and a greater ability to adjust mass-based Pmax (Pmax,m) to variations in leaf N and P concentration appeared to be key traits for withstanding prolonged drought in the Cerrado. In C. americana, increases in SLA and higher nutrient-use efficiency appeared to be important in maintaining high rates of Pmax,m in the seasonally flooded Pantanal. Flexibility in physiology and resource-use efficiency may allow these species to survive and persist in habitats with broadly differing hydrology. © 2014 Springer Science+Business Media Dordrecht.


Dalmolin A.C.,Programa de Pos Graduacao em Fisica Ambiental | Dalmagro H.J.,Programa de Pos Graduacao em Fisica Ambiental | Lobo F.A.,Programa de Pos Graduacao em Fisica Ambiental | Antunes Jr. M.Z.,Programa de Pos Graduacao em Agricultura Tropical | And 2 more authors.
Photosynthetica | Year: 2013

Vochysia divergens Pohl is considered to be a flood-adapted, light-demanding pioneer species that has been invading grasslands of the Brazilian Pantanal. In these areas, a successful invasion requires an ability to tolerate physiologically wide fluctuations in surface hydrology and shading induced by a dense cover of grasses and other vegetation. We evaluated how flooding and shading affected the photosynthetic performance of V. divergens saplings by measuring light-saturated gas exchange (net photosynthetic rate, P N; stomatal conductance, g s), and intercellular CO2 (P N/C i) and photosynthetic photon flux density (P N/PPFD) response curves over a 61-d field experiment. Shading and flooding reduced significantly light-saturated P N and g s and affected multiple aspects of the leaf gas exchange response of V. divergens to variations in PPFD and CO2. Flooding influenced the physiology of this species more than shading. Given the success of V. divergens at invading and expanding in seasonally flooded areas of the Pantanal, the results were surprising and highlighted the physiological ability of this species to tolerate suboptimal conditions. However, the consistently higher light-saturated P N and g s under nonflooded conditions suggested that the invasive success of V. divergens might not be related to its physiological potential during flooding, but to situations, when flooding recedes during the dry season and soil water availability is adequate. © 2013 Springer Science+Business Media Dordrecht.

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