Respostas fisiológicas de plantas amazônicas de regiões alagadas às mudanças climáticas globais

Abstract

-(Physiological responses of Amazonian flooded plants to the global climate change). According to the last report of IPCC (Intergovernmental Panel of Climatic Change, 2007) an increase in atmospheric CO 2 concentration to ca. 0.072% is predicted to occur until the middle of this century. As a result, a tandem elevation of temperature of ca. +3 °C and a decrease in precipitation are to be expected. It has also been suggested that this scenario may lead to a gradual substitution of the tropical forest for savanna-like vegetation in Eastern parts of the Amazon. Within this perspective, a worth question is how the tree species that make up the Amazonian floodplains will respond to the global climatic change? Although predictions have been quite pessimistic, flooding of part of the Amazon will continue to occur for several years and it is important to understand its synergistic effects within the scenario of climate change. In this work, features related to plant metabolism and hormonal signaling during flooding is revised, and the possible effects that the climatic changes might have on plants from the Amazon are discussed. The information available in the literature suggests that under flooding, plants tend to mobilize storage compounds to supply carbon demand needed for maintenance metabolism under the effect of stress caused by the lack of oxygen. In contrast, under elevated CO 2 concentration, plants tend to increase photosynthesis and biomass. With an increase of about 3 °C these parameters may increase even more. Alternatively, with flooding, there is a general decrease in growth potential and it is possible that while favorable conditions of elevated CO 2 and temperature prevail, the positive effects may be counterbalanced by the negative effects of flooding. Thus, the physiological responses might be imperceptible or promote further growth up to the middle of the 21 st Century for most species that occur in the floodplains. However, if temperature and CO 2 levels surpass the threshold of optimal conditions for most plants, a decrease in physiological activity is to be expected.

Antioxidant activity and fermentative metabolism in the plant Erythrina crista-galli L. under flood conditions

“…The accumulation of lactate under low O 2 concentrations occurs before ethanol production in the root cells. This dropin pH favours the catalytic activity of PDC, which is responsible for modulating lactate conversion into ethanol under hypoxic or anoxic conditions (GRANDIS et al, 2010). This explains the results obtained in this study regarding the activity of these enzymes ( Figures 4A and B).…”

“…The majority of studies on signalling pathways and flood tolerance were performed on plants such as rice and Arabidopsis (GRANDIS et al, 2010), and little is currently known regarding the mechanisms involved in the acclimation of forest plant species subjected to flooding stress. Understanding these mechanisms is of great importance and will have a positive impact on elucidating the relationship between the biodiversity of forest species and environmental conditions.…”

Anatomical and morphological modifications in response to flooding by six Cerrado tree species

“…Plants under oxygen deficiency (hypoxia) tend to mobilize storage reserves to meet the demand required to maintain carbon metabolism (Kozlowski 1997;Kolb et al 1998;Albrecht et al 2004;Ferreira et al 2009a;Grandis et al 2010). Depending on the species, cotyledons can contain large amount of reserve compounds that are consumed during germination and early growth of the plant (Santos & Buckeridge 2004;Corte et al 2006).…”

Influence of water regime on initial growth and essential oil of Eucalyptus globulus

“…According to GRANDIS et al (2010), plants under conditions of excessive ground water present reduced energy efficiency, since roots under anoxia present difficulties in maintaining the energy flow in the tissues. In addition, MEDRI et al (2007), studying morphoanatomic changes of Lithrae molleioides, subjected to flooding, that under excessive water conditions, plants presented lower starch content in the stem and lower production of secretory structures.…”