In the pursuit of knowledge on the biological behavior of Brazilian Atlantic Forest tree species, this study evaluated the susceptibility of the light-demanding species, Schinus terebinthifolia Raddi., Pseudobombax grandiflorum (Cav.) A. Robyns and Joannesia princeps Vell., and of the shade-tolerant species, Hymenaea courbaril L. var. stilbocarpa and Lecythis pisonis Camb, to photoinhibition and acclimation capacity. These species were first cultivated under two irradiance conditions, I20 (20% direct sunlight radiation) and I100 (all-sky or direct sunlight) and then transferred from I20 to I100. The effects of the sudden increase in light radiation intensity on photosynthetic activity were then evaluated through chlorophyll (Chl) fluorescence imaging, HPLC xanthophylls analysis, and cell membrane lipid peroxidation measurements. Light-demanding species were found to present a higher photochemical efficiency and higher acclimation capacity under high light irradiance than shade-tolerant species. The higher photoinhibition tolerance observed in light-demanding species was associated to their higher capacity for photochemical dissipation and dissipation of excess excitation energy via the xanthophyll cycle, leading to a lower ROS generation. The obtained results suggested that a knowledge of acclimation capacity, by means of Chl fluorescence imaging yields, is a useful indicator of species successional grouping., L. Dos Anjos, M. A. Oliva, and K. N. Kuki., and Obsahuje bibliografii
Photosynthetic organs are often characterized by anthocyanins being accumulated either in the epidermal or in the mesophyll cells making these tissues to turn reddish-brown in colour. It has been hypothesized that these pigments protect underlying chloroplasts from light-stress because they absorb photons of the photosynthetically active waveband. However, the photoprotective role of anthocyanins has not been undoubtedly shown on a broad range of species. In this study, green and anthocyanic areas of leaves of Pelargonium × hortorum, the latter possessing variable levels of anthocyanins, were compared using pigment analysis and pulse amplitude modulated in vivo chlorophyll (Chl) fluorescence. Quenching analysis of the induction and dark relaxation curves of slow Chl fluorescence kinetics showed that at photoinhibitory conditions [by applying above-saturation light intensity of 1,600 μmol(quantum) m-2 s-1 white light at low (4°C) temperature], anthocyanic areas were at least equally sensitive to photoinhibition as green leaf areas. In fact, the level of photoinhibition tended to be proportional to the level of anthocyanin accumulation suggesting that this characteristic was indicative of the photoinhibitory risk. The results of the present study clearly show that anthocyanins in leaf areas of Pelargonium do not afford a photoprotective advantage., G. Liakopoulos, I. Spanorigas., and Obsahuje bibliografii
Both molecular and palaeoecological methods enable us to study past changes in plant distribution. The results of recent phylogeographical studies have demonstrated that Central Europe was not only at a crossroads of postglacial migration routes, but also an area where many species might have survived during glacial periods. and Tomáš Fér, Karol Marhold.
Leaf gas exchange of terrestrial and epiphytic orchids from the Atlantic Rainforest in northeast Brazil was investigated under artificial growth conditions. The terrestrial orchids showed higher values of all photosynthetic parameters in comparison to epiphytic ones. There was a close relationship between PN and gs for both terrestrial and epiphytic orchids. Taken together, our results demonstrated that the photosynthetic parameters were related to the specific growth habits of the orchids under study., M. V. Pires ... [et al.]., and Obsahuje bibliografii
The aim of this study was to characterize the key physiological aspects of three sugarcane cultivars (RB92579, RB867515 and RB872552) under biological nitrogen fixation (BNF). Plants were generated in tubes containing aseptic substrates and these plants were transferred to pots containing washed sand, but watered with a mineral fertilizer, and inoculated with a mixture of five diazotrophic bacteria three times at seven-day intervals. Under BNF, all of the cultivars contained half of their total leaf nitrogen content and 50% less shoot dry mass. The leaves of plants under BNF showed approximately 65% less of the total protein content (TP). The
gas-exchange control plants had twice the CO2 assimilation rates than the BNF plants. The activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) was increased in all cultivars under BNF when compared with the control; thus, the content of hydrogen peroxide (H2O2) was also increased in these plants. The results of this study indicate that after acclimatization, the inoculation of young plants from tissue culture with diazotrophic bacteria could supply approximately 50% of their nitrogen requirement., C. D. Medeiros ... [et al.]., and Obsahuje bibliografii
The gas-exchange characteristics, leaf water potential and chlorophyll (Chl) a fluorescence of oil palm (Elaeis guineensis Jacq.) seedlings subjected to water stress and recovery were investigated in a greenhouse experiment. At 24 days after imposition of stress, leaf water potential in water-stressed seedlings was doubled compared to that of control and there was a drastic decline in gas-exchange parameters viz. photosynthesis, transpiration, and stomatal conductance. Water stress did not irreversibly affect gas-exchange parameters and quantum efficiency of photosystem II, as seedlings exhibited total recovery of photosynthetic apparatus by 12th day of rehydration. These findings indicate that oil palm exhibits physiological plasticity to water stress during the seedling stage. and K. Suresh ... [et al.].