Ultrastructure Of Photosynthetic Apparatus Research Articles

Effects of Sucrose on Structure and Functioning of Photosynthetic Apparatus of Galanthus Nivalis L. Leaves Exposed to Chilling Stress

The effects of sucrose (Suc) on the ultrastructure of photosynthetic apparatus (PSA) and its functional characteristics were investigated in chilling-tolerant Snowdrop (Galanthus nivalis L.). On the first stage of the experiments, the plants were acclimated at +5 °C and then their detached leaves were subjected to low temperatures (–5 or –15 °C) in the presence of Suc (0.02 or 0.1 M). The electron microscopic analysis showed that Suc treatment at +5 °C induced granal thylakoid elongation and reduction of number of thylakoids. At negative temperatures, the number of thylakoids per granum and the height of grana increased after Suc treatment. The data obtained by method of slow induction chlorophyll fluorescence showed that sharp drop in functional parameters (Fv/Fm, qP, and ETR) with decrease in temperature from +5 to –15 °C was prevented in part by treating of leaves with 0.02 M Suc and, to a large extent, after exposure of leaves in 0.1 M Suc solution. Non-photochemical quenching of fluorescence increased with decrease in the temperature to –15 °C and stabilized with Suc-treatment. The effect of Suc on G. nivalis PSA ultrastructure and functioning suggests that their chloroplasts are capable of osmotic adjustment in response to cold stress.

Ультраструктура фотосинтетичного апарату та вміст пігментів у плаваючих і підводних листках Nuphar lutea та Nymphaea alba

Ультраструктура фотосинтетичного апарату та вміст пігментів у плаваючих і підводних листках Nuphar lutea та Nymphaea alba

Photosynthesis and ultrastructure of photosynthetic apparatus in tomato leaves under elevated temperature

The microstructure of leaves and ultrastructure of chloroplasts were examined in tomato (Lycopersicon esculentum L.) plants treated with elevated temperature. Plants were exposed to 35°C for 30 d after florescence. The plants grown continuously under 25°C served as controls. Compared with the controls, the net photosynthetic rate (P N) in stressed plants decreased significantly. Stomatal conductance, intercellular CO2 concentrations, the rate of transpiration, and the limitation of stomatal conductance showed that the decrease in P N was caused mainly by nonstomatal restrictions. Meanwhile, stomata density increased significantly in the stressed plants. The stomata status of opening and closing became disorganized with a prolonged 35°C exposure. The damage of chloroplast membrane occurred earlier and was more serious in the plants under elevated temperature. At the same time, the thylakoids were loosely distributed with lesser grana, but the number of lipid droplets increased in chloroplasts. The number of starch grains in chloroplasts increased first and then decreased. In addition, the length of the main nerve in leaves increased and the main vein showed distortion in the plants stressed by 35°C. An increase was observed in the number of cells on the abaxial side of the main vein and these cells were overly congregated. The thickness of a vertical section became thinner in the stressed leaves. The cells of the upper epidermis thinned, and the ratio of palisade tissue to spongy tissue decreased. Generally, the photosynthetic apparatus of tomato changed significantly and the changed chloroplast ultrastructure might be one of the important reasons that caused the decrease of P N under 35°C.

Spent metal working fluids produced alterations on photosynthetic parameters and cell-ultrastructure of leaves and roots of maize plants

In this work we assess the capacity of maize (Zea mays) plants to phytoremediate spent metal working fluids (MWFs) and its effects on photosynthesis and ultrastructure of mesophyll and root cells. A corn-esparto fibre system patented by us has been used to phytoremediate MWFs in hydroponic culture. Furthermore, a plant growth promoting rhizobacteria (PGPR) has been used to improve the process. The results show that this system is capable of significantly reducing the chemical oxygen demand, under local legislation limits. However, plant systems are really damaged, mainly its photosynthetic system, as shown by the photosynthetical parameters. Nevertheless, strain inoculated improves these parameters, especially Hill reaction. The ultrastructure of photosynthetic apparatus was also affected. Chloroplast number decreased and becomes degraded in the mesophyll of MWFs treated plants. In some cases even plasmolysis of chloroplast membrane was detected. Early senescence symptoms were detected in root ultrastructural study. Severe cellular damage was observed in the parenchymal root cells of plants grown with MWFs, while vascular bundles cell remained unchanged. It seems that the inoculation minimises the damage originated by the MWFs pollutants, appearing as less degenerative organelles and higher chloroplast number than in non-inoculated ones.