Chloroplastid pigment contents and chlorophyll a fluorescence in Amazonian tropical three species

The photosynthetic dynamics of the tropical pioneer species, Byrsonima sericea DC., were studied during the regeneration process of a native forest by evaluating ecophysiological (gas exchange, chlorophyll a fluorescence and photosynthetic pigment contents) and anatomical parameters of plants in sunny and shady environments. Ecophysiological evaluations were carried out monthly for one year, encompassing both a dry and a rainy season. Byrsonima sericea DC. presents anatomical plasticity that enables it to establish in environments with contrasting light regimes. In sunny conditions, it produced a thicker leaf (about 420 mm) and flat adaxial epidermis, whilst in the shade, leaves had a thinner convex adaxial epidermis (about 395 mm). No differences were found in the compositions of the pigments in the different environments, however, during the dry season, the plants presented a significantly higher concentration of photosynthetic pigments. In the sun, plants showed decreases in Fv/F0 ratio (in the rainy season) and NPQ (in the dry season), but no difference was observed between plants that were in the sun or in the shade. A significantly higher net photosynthetic rate was found only in the rainy season in the plants in the sun, compared to shaded plants (9.9±0.8 and 7.4±0.3 μmol m -2 s -1 , respectively). Significant increase in transpiration was observed in plants in the shade during the dry season, but no alterations were observed in the water use efficiency. Ecophysiological data suggest that mainly plants overexposed to the sun underwent water limitations during the dry season and that, in the rainy season, these plants increased their net photosynthetic rate, possibly due to the greater drainage force resulting from increased growth during this period. Data suggest that anatomic alterations, namely the convex adaxial epidermis, could aid in the supply of light to shaded plants during both seasons, precluding changes in the pigments, such as the increase in chlorophyll b usually observed in shaded plants, but not detected in the present study. Another consequence of the greater quantity of light captured by these shade plants is that during the dry season their net photosynthetic rate was not different from that of plants in a sunny environment. However, when water was not a limiting factor, a better photosynthetic performance was observed in this pioneer specie in open spaces.Key words: Atlantic forest species; photosynthetic adaptation; leaf anatomy; sun overexposure; shaded plants. RESUMOA dinâmica fotossintética da espécie pioneira tropical Byrsonima sericea DC. foi estudada durante o processo de regeneração de uma mata nativa por avaliações ecofisiológicas (trocas gasosas, fluorescência da clorofila a e conteúdo de pigmentos fotossintéticos) e parâmetros anatômicos das plantas em ambientes ensolarados e sombreados. As avaliações ecofisiológicas foram feitas mensalmente por um ano e os dados foram agrupados em estação seca e chuvosa. Byrsonima sericea DC. apresentou plasticidade anatômica que a ...

Section: Discussionsupporting

confidence: 82%

Photosynthetic performance and anatomical adaptations in Byrsonima sericea DC. under contrasting light conditions in a remnant of the Atlantic forest

Silva

Oliveira

Cunha

et al. 2010

“…The presence of lower levels of chlorophyll a, b, and total chlorophylls in the EXU is corroborated by the findings of Morais et al (2007), who also observed lower levels of these pigments in tropical tree species (Bertholletia excelsa, Carapa guianensis, and Dipteryx odorata) exposed to increased light intensity. Chlorophyll is constantly synthesized and destroyed in the presence of light (photo-oxidation), but under high light intensity there is a higher rate of decomposition, with the established equilibrium occurring at a lower concentration (Kramer and Kozlowski, 1979).…”

Section: Discussionsupporting

confidence: 70%

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

Lage-Pinto

Bernini

Oliveira

et al. 2012

Gas exchange, chlorophyll a fluorescence, and photosynthetic pigments of Xylopia sericea A. 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 União Biological Reserve (known as REBIO União), 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 F v /F m e F m /F o were 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.

“…The decrease in the ratios Chl a:b and Chl total :Carot in plants of C.echinata after periods of exposure to direct sunlight (Figure 4) is one of the immediate responses of shade species when exposed to higher irradiance (Demmig-Adams and Adams, 2006;Morais et al, 2007;Magalhães et al, 2009) light-gathering antennas (Kitajima and Hogan, 2003;Laisk et al, 2005;Magalhães et al, 2009). This strategy protects the photosystems from photo-oxidative damage caused by high irradiance (Tan et al, 2000;Marenco et al, 2001;Reyes-Díaz et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Morphological and physiological adjustments of Brazilwood (Caesalpinia echinata Lam.) to direct solar radiation

Mengarda

Milanez

Silva

et al. 2012

This study aimed to characterize the alarm and resistance phases of stress of Caesalpinia echinata under intense irradiance in order to better define its position on forest succession. The alarm phase was identified by rapid reduction in the maximum quantum yield of PSII primary photochemical reactions (φP0 = F V /F M ) and Performance Index (PI ABS ) followed by total leaf abscission in the first week of exposure to direct sunlight. The new leaves grown showed recovery of chlorophyll a parameters, increase in blade thickness, elongation of the palisade and spongy parenchymas, higher water content, and reduction of specific leaf area. These changes were associated with the osmoprotector of sucrose and antioxidative of raffinose effects, which indicate an efficient adjustment system to intense irradiance in the resistance phase of stress. However, the continuous decrease in photosynthetic pigments in the resistance phase combined with the photodamage in the fluorescence of Chl a and total abscission of leaves in the alarm phase are strong indications that C. echinata is a shade and late or climax species in forest succession.