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

Abstract

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 ...

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

“…However, when water was not a limiting factor, a better photosynthetic performance was observed in this species in conditions of higher light intensity. Similar results were reported by Silva et al (2010) in studies carried out on the pioneer species Byrsonima sericea during the dry and rainy season in the REBIO União.…”

“…The values of the gas exchange variables registered in the present study for X. sericea and S. guianensis are situated within the parameters observed for other tropical tree species (Baker et al, 1997;Eschenbach et al, 1998;Marenco et al, 2001;Costa and Marenco, 2007;Gonçalves et al, 2009;Silva et al, 2010). The species X. sericea and S. guianensis exhibited high values of correlation between A and g s in the dry season, suggesting that their stomata respond significantly to the variations in light and water availability.…”

“…A higher level of carotenoids was observed in the dry season in relation to the rainy season in the ECU for S. guianensis. Silva et al (2010) obtained similar findings for Byrsonima sericea in the REBIO União, suggesting that the increase in pigment content in the dry season may have occurred due to lower relative water content in the leaves caused by the decrease in water availability during this season.…”

“…These results are corroborated by Sarijeva et al (2007), who studied Ginko biloba L. and Fagus sylvatica L., and by Silva et al (2010), who studied Byrsonima sericea in contrasting light environments. Accumulating more carotenoids is a physiological strategy for the protection of plants against photoinhibition because these pigments efficiently dissipate the excess of solar radiation in a non-destructive manner, avoiding damage to the PSII (Demmig- Adams et al, 1989), which in turn corroborate the non-photochemical (NPQ) dissipation data discussed above.…”

Ecophysiological studies of two andean forest contrasting species Abatia parviflora and Myrcianthes leucoxyla under Bogotá conditions, Colombia

“…Photosynthesis and stomatal conductance studies of tropical tree species under various conditions are considered of great importance to understand the role of the tropical forest in regional water and carbon cycles, considering that abiotic factors such as light, seasonal variations of temperature and water can drastically influence plant responses (Silva et al, 2010). Analysis of physiological responses to seasonal variation is necessary to identify the interaction potentials between tropical forests and climate change (Hogan, 1988).…”