Frederico Lage-Pinto

Photosynthetic analyses of two native Atlantic Forest species in regenerative understory of eucalyptus plantation

Gas exchange, chlorophyll afluorescence, and photosynthetic pigments of Xylopia sericeaA. St.-Hil. and Siparuna guianensis Aubl. were evaluated during the rainy season and the dry season (2009-2010) in three understories with different ecological conditions (irradiance, water availability, and temperature) located in the Uniao Biological Reserve (known as REBIO Uniao), at Rio de Janeiro State, a natural forest understory, eucalyptus understory under regeneration, and understory of eucalyptus plantation with 18-year-old trees that were removed 1 year before. The lowest values of Fv/Fme Fm/Fowere observed in the exposed understory for both seasons, with lower values in the dry season, suggesting that reduced water availability potentializes the photoinhibitory process. For both species of the exposed understory it is suggested the occurrence of photoprotection, given that an increased proportion of carotenoid pigments in relation to the chlorophylls were verified. Both species still exhibited dynamic photoinhibition after 1 year of exposure to full sunlight (exposed understory) in both seasons, but more markedly so in the dry season, though they belong to early stages of ecological succession. Based on the results, it is suggested that these species are indicated for planting in degraded areas and that the cutting of eucalyptus trees as management practice should be performed in a gradual manner, during the rainy season, in order to minimize stress on these species.

Ecophysiological adaptation and metal accumulation in water hyacinth from two tropical rivers

The ecophysiological adaptations of water hyacinth (metal hyperaccumulator) under adverse environmental conditions are not yet clearly elucidated. This work evaluated photosynthetic pigments and chlorophyll a fluorescence in water hyacinth plants sampled in different regions (upper, middle and lower) of Paraiba do Sul river (PSR) and Imbe river, Brazil. Additionally Mn, Fe, Zn, Cu, Cr, Pb and Ni were quantified on the shoots and roots. Roots were the preferential site of metal accumulation. Cromium was not detected in the shoots. Iron and Mn were the elements detected in higher concentrations in all samples. Zinc and Cu were detected in higher concentrations in roots of plants from middle and upper PSR, sites of higher anthropogenic activity. The highest concentrations of almost all metals were verified in plants from middle PSR. Regarding photosynthetic adaptations, plants from middle and upper PSR showed the highest concentrations of photosynthetic pigments, as well as the highest values of Fv/Fm and Fv/F0. The photosynthetic performance of plants suggests that they are not under stress conditions, even in regions of higher anthropogenic activity. Positive correlation was observed among nonphotochemical quenching and carotenoids, suggesting dissipation of energy in the form of heat as an strategy to keep the stable photochemical photosynthesis functioning, confirmed by values of the Fv/Fm. It is possible that such adaptative strategy is efficient as a long term response to stress factors, once literature data suggest that this is not a preferential path for photosynthesis in stress circumstances under short time controlled conditions.

Structural and ecophysiological alterations of the water hyacinth [Eichhornia crassipes (Mart.) Solms] due to anthropogenic stress in Brazilian rivers

In this work, the structural and ecophysiological a lterations (chlorophyll a fluorescence and photosyn thetic pigments), and quantification of Cr, Pb and Zn in t he leaf limb, petiole and younger and older roots o f water hyacinth from the lower, medium and upper Paraiba driver (PSR) and Imbe river were evaluated. Th e plants from the medium and upper PSR (more industrialized and populated regions) exhibited lower turgid cell in the root cortex, less root hairs and leaf epidermis, chlorop lasts with plastoglobules and increased stroma volu me. Higher concentrations of metals were observed in the young er and older roots from the medium PSR plants. The results suggested that the plants from more anthropized reg ions were able to maintain the maximum quantum yiel d (Fv/Fm) which was a result from the metabolic fitting, incr easing the non-photochemical quenching, reducing to tal chlorophyll/carotenoids and leading to the structur al modifications.

Ecofisiologia de duas espécies tropicais em uma plantação abandonada de eucalipto: efeito da remoção da serapilheira e sazonalidade

The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a luorescence, and content of photosynthetic pigments) of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalypt (Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae)). The study was conducted at the Uniao Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after ive years of litter removal. The removal of plant litter did not inluence the ecophysiological responses of the species. There was however signiicant seasonal variation. During the dry period, intercellular CO 2 concentration (C i ), transpiration (E), and stomatal conductance (g s ) were decreased, while intrinsic eficiency of water use (IWUE), non-photochemical quenching (NPQ), and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for F v /F m (maximum quantum eficiency) and F m /F o (ratio of luorescence yields for open and closed states) indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A) during the dry period. The data indicated that X. sericea was photosynthetically more eficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed.

Estresse luminoso em plântulas de jequitibá-rosa (Cariniana legalis, Lecythidaceae): monitoramento da capacidade de aclimatação fotossintética sob duas intensidades de luz

The knowledge of the capacity for acclimation and establishment of plant species is important for the implementation of management programs and ecological restoration of degraded ecosystems. Ecophysiological studies were performed (gas exchange, chlorophyll a fluorescence and photosynthetic pigments content) to evaluate the effect of light intensity on activity and photosynthetic capacity of jequitiba-rosa (Cariniana legalis Mart. Kuntze). The responses of seedlings subjected to the condition of full sun suggest that direct radiation could be a stressor for this species, affecting their performance, although photosynthetic acclimation with increasing light intensity was observed.