Magdalena Gapińska

Changes in the ultrastructure of chloroplasts and mitochondria and antioxidant enzyme activity in Lycopersicon esculentum Mill. leaves sprayed with acid rain

Abstract The effects of simulated acid rain (AR) on the ultrastructure of chloroplasts and mitochondria as well as the antioxidant defence system were investigated in Lycopersicon esculentum Mill. leaves. Analyses carried out 0.5, 3.0, 24, 48, 72 and 96 h after a single spraying of AR (pH 1.8) indicated alterations in 13% of chloroplasts and 95% of mitochondria, at the end of experiment. Disturbances in the structure of these organelles were accompanied by changes in activities of catalase (CAT), ascorbate peroxidase (APx), superoxide dismutase (SOD), including CuZnSOD, glutathione peroxidase (GSH-Px) and glutathione transferase (GST). AR caused a decrease in GSH-Px and CAT activities starting 24 h after treatment but an increase in SOD and its izoenzyme CuZnSOD activities at 72 and 96 h. On the other hand, GST activity significantly increased at 0.5–3 and after 48–72 h while APx activity increased at all experimental times. These data suggest that high APx and GST activities in L. esculentum were not sufficient to protect mitochondria but they might have been sufficient to prevent ultrastructural damage of chloroplasts.

Silver nanoparticles: a mechanism of action on moulds

Silver nanoparticles (AgNPs) are widely used in all branches of industry. However, their mechanisms of action towards moulds have not been studied yet. Thus we conducted this study in which we have used laser desorption/ionization time-of-flight mass spectrometry (LDI-ToF-MS) analysis to determine metabolomic changes, and microscopic analysis (transmission electron microscopy, fluorescent microscopy) to observe changes in mould cells. The AgNP treatment caused the downregulation of 162 (15 ppm) and 284 (62 ppm), and 19 (15 ppm) and 29 (62 ppm) metabolites of Aspergillus niger and Penicillium chrysogenum, respectively. All influenced features were below m/z 600 (mass-to-charge ratio). We have observed silver ions and their clusters (Ag, Ag2, and Ag3) accumulated in the mould mycelium. As well as, mono-silver ion adducts with nucleotide derivatives (Coenzyme A), amino acids (phenylglycine), peptides (LeuSerAlaLeuGlu) and lipids (fatty acids, diacylglycerophosphoglycerols, monoglicerides and glycerophospholipids). The ultrastructure analysis revealed many sever alterations due to the action of AgNPs, such us shortening and condensation of hyphae, ultrastructural reorganisation, cell plasmolysis, increased vacuolisation, numerous membranous structures, collapsed cytoplasm, accumulation of lipid material, condensed mitochondria, disintegration of organelles, nuclear deformation, condensation and fragmentation of chromatin, creation of apoptotic bodies, as well as a new inside cell wall in P. chrysogenum.

Effects of chilling on the root cell ultrastructure of two soybean cultivars

Two soybean [Glycine max (L.) Merr.] cultivars: Aldana (more resistant) and Essor (less resistant to low temperature) were subjected to chilling at 5°C for 24 h, and then the ultrastructure of the root meristem cells was investigated. The ultrastructure of control root cells of the tested cultivars differed in the number of condensed mitochondria, plastids with phytoferritin, deformed vacuoles, as well as multivesicular bodies (MB) in cytoplasm and vacuoles. Chilling induced concentric endoplasmic reticulum (ER) arrangement in both soybean cultivars, while the circular Golgi apparatus (GA) occurred only in cv. Essor and MB in the cytoplasm of cv. Aldana cells. Additionally, in cv. Aldana chilling increased the number of condensed mitochondria, MB in vacuoles and multilamellar structures (MS) in cytoplasm whereas in cv. Essor it enlarged the population of plastids with phytoferritin and the number of MB in cytoplasm. After chilling treatment the population of deformed vacuoles with phenolic compounds in the form of electron dense granules increased but the number of multilamellar structures (MS) in the vacuoles of both cultivars decreased. The ultrastructural changes induced by the chilling stress were not lethal but rather adaptive, especially in more resistant cv. Aldana.

Salt-mediated changes in leaf mesophyll cells of Lycopersicon esculentum Mill. plants

Five-week-old tomato plants (Lycopersicon esculentum) cv. Perkoz grown in pots containing garden soil in a growth chamber were submitted to 50 or 150 mM NaCl for 1 h, 2 and 5 days. Tomato leaf anatomy generally did not change after short time salinity, except 5-day-treatment with 150 mM NaCl, where changed cell shape (shrunk and deformed) simultaneously with increased volume of intercellular spaces (IS) were observed. Although leaf hydration (H) depleted only 1 h after 150 mM NaCl treatment both salt concentrations generated two coexisting populations of salt-affected mesophyll cells: (i) slightly-affected (Sl-A) which showed incipient plasmolysis or slightly changed shapes, and (ii) severely-affected (Sv-A) which showed severe plasmolysis; serious deformation of cell shape or disorganization including cell degeneration. In Sl-A cells salinity changed location and shape of chloroplasts which were: more rounded, with oversized starch grains (SG) (2d) or more flat (5d). Salt-mediated changes were becoming more distinguished and pronounced with length of 150 mM NaCl treatment. The amount of salt-affected cells was changing during the experiment and depended on the salt concentration. In 50 mM-treated plants salt-affected cells appeared 1 h after treatment (~40%) and raised up to 78% on 2nd day, however the population of Sl-A cells dominated. In 150 mM NaCl-treated plants the percentage of affected cells raised during the experiment from 75% to 99%. Firstly Sl-A cells dominated, but on the 5th day the majority was Sv-A. Salt-affected cells were distributed quite evenly in palisade or spongy mesophyll, except 2 d after treatment with 50 mM NaCl, when their number was higher in the palisade mesophyll. Sv-A cells in the spongy mesophyll were located mostly near the bundle while in the palisade mesophyll more irregularly. Different susceptibility of cells to salt stress might be the consequence of an unequal distribution of osmotic stress and subsequent ionic stress or physiological state of cells.