Increase of harmful radiation to the Earth’s surface due to ozone depletion results in higher exposure to harmful ultraviolet- B radiation (UV), while fluctuations in seawater salinity may alter water density, ionic concentration, nutrient uptake, and osmotic pressure. This study evaluated the effects of salinity and UV on metabolism and morphology of Acanthophora spicifera (M.Vahl) Børgesen. Water with 30 and 37 psu [g(salt) kg-1(sea water)] was used for experiments during 7 d of exposure to UV (3 h per day). We demonstrated that UV treatment predisposed, irrespective of salinity, A. spicifera to a decrease in its growth rate and cell viability, as well as affected its morphological parameters. After exposure to PAR + UVA + UVB (PAB), samples showed structural changes and damage, such as increasing cell wall thickness and chloroplast disruption. Our results indicate that UV led to dramatic metabolic changes and cellular imbalances, but more remarkable changes were seen in samples exposed to high salinity., D. T. Pereira, C. Simioni, L. C. Ouriques, F. Ramlov, M. Maraschin, N. Steiner, F. Chow, Z. L. Bouzon, É. C. Schmidt., and Obsahuje bibliografii
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) is one of the key enzymes involved in assimilation of CO2 in chloroplasts. Phylloplane microfungi and their metabolites have been reported to affect the physiology of host plants, particularly, their photosynthesis. However, information is lacking on the effect of these microflora on the physiology of chloroplasts. The current study emphasized the impact of two dominant phylloplane fungi, Aspergillus niger and Fusarium oxysporum, on activity of Rubisco in tomato chloroplasts. Ergosterol, which is a component of only fungal cell membranes and is not synthesized by plants, have been demonstrated to elicit activity of Rubisco. In the present study, it was demonstrated through in silico, in vitro, and in vivo approaches. Results demonstrated that the fungal metabolites, which contained ergosterol, could double Rubisco activity. Maximum carboxylation rate of Rubisco increased also in ergosterol-treated plants. Michaelis-Menten constant of Rubisco was also slightly affected. Ergosterol was found also to influence and enhance the binding of CO2 and ribulose-1,5-bisphosphate to Rubisco. Therefore we can postulate that the physiology of the chloroplast is probably influenced by phylloplane microfungi., J. Mitra, P. Narad, P. K. Paul., and Obsahuje bibliografii