Elektronová mikroskopie pracující s velmi nízkými energiemi řádu jednotek nebo jen několika desítek elektronvoltů se v poslední době těší velké pozornosti. Její výhody se využívají především při studiu dynamických procesů na povrchu pevných látek. Článek popisuje modulární mikroskop navržený a vyrobený firmou Delong Instruments, a. s., který takováto pozorování umožňuje., Martin Mynář, Radovan Vašina, Vladimír Kolařík., and Obsahuje seznam literatury
První sériově vyráběný elektronový mikroskop (EM) uvedla na trh firma Siemens před 80 lety v roce 1939 (obr. 1). Teprve o deset let později byl zkonstruován první EM v Československu skupinou mladých pracovníků kolem profesora Aleše Bláhy v Brně. Z tohoto nenápadného počátku vyrostla průmyslová chlouba Brna a celého státu - několik firem zde vyrábí téměř třetinu světové produkce EM. Přitom se nejedná o zanedbatelné odvětví "high-tech" průmyslu, neboť představuje trh o velikosti asi 3,2 miliardy dolarů za rok a v příštích letech má růst více než 7% tempem - především díky poptávce rozvíjejícího se nanotechnologického průmyslu., Jan Valenta., and Obsahuje bibliografické odkazy
This issue also brings an interview with Dr. Vilém Neděla, the head of Environmental Electron Microscopy of the Institute of Scientific Instruments of the CAS on the Quanta 650 FEG scanning electron microscope (SEM), which is used for high-resolution imaging and semi-quantitative X-ray microanalysis of both conductive and non-conductive specimens at nanometer resolution. and Magdaléna Selingerová.
Nitrogen is an essential factor for normal plant and algal development. As a component of nucleic acids, proteins, and chlorophyll (Chl) molecules, it has a crucial role in the organization of a functioning photosynthetic apparatus. Our aim was to study the effects of nitrogen starvation in cultures of the unicellular green alga, Chlamydomonas reinhardtii, maintained on nitrogen-free, and then on nitrogen-containing medium. During the three-week-long degreening process, considerable changes were observed in the Chl content, the ratio of Chl-protein complexes, and photosynthetic activity of the cultures as well as in the ultrastructure of single chloroplasts. The regreening process was much faster then the degradation; total greening of the cells occurred within four days. The rate of regeneration depended on the nitrogen content. At least 50% of the normal nitrogen content of Tris-Acetate-Phosphate (TAP) medium was required in the medium for the complete regreening of the cells and regeneration of chloroplasts., É. Preininger, A. Kósa, Z. S. Lőrincz, P. Nyitrai, J. Simon, B. Böddi, Á. Keresztes, I. Gyurján., and Obsahuje seznam literatury
Changes in Hill reaction activity (HRA) and ultrastructure of mesophyll cell (MC) chloroplasts were studied during the ontogeny of third leaf of maize plants using polarographic oxygen evolution measurement, transmission electron microscopy, and stereology. The chloroplast ultrastructure was compared in young (actively growing), mature, and senescing leaves of two different inbreds and their reciprocal F1 hybrids. Statistically significant differences in both HRA and MC chloroplast ultrastructure were observed between different stages of leaf ontogeny. Growth of plastoglobuli was the most striking characteristic of chloroplast maturation and senescence. The chloroplasts in mature and senescing leaves had a more developed system of thylakoids compared to the young leaves. Higher HRA was usually connected with higher thylakoid volume density of MC chloroplasts. and J. Kutík ... [et al.].
Differences in ultrastructural parameters of mesophyll cell (MC) chloroplasts, contents of photosynthetic pigments, and photochemical activities of isolated MC chloroplasts were studied in the basal, middle, and apical part of mature or senescing leaf blade of two maize genotypes. A distinct heterogeneity of leaf blade was observed both for structural and functional characteristics of chloroplasts. In both mature and senescing leaves the shape of MC chloroplasts changed from flat one in basal part of leaf to nearly spherical one in leaf apex. The volume density of granal thylakoids decreased from leaf base to apex in both types of leaves examined, while the amount of intergranal thylakoids increased in mature leaves but decreased in senescing leaves. The most striking heterogeneity was found for the quantity of plastoglobuli, which strongly increased with the increasing distance from leaf base. The differences in chloroplast ultrastructure were accompanied by differences in other photosynthetic characteristics. The Hill reaction activity and activity of photosystem 1 of isolated MC chloroplasts decreased from leaf base to apex in mature leaves. Apical part of senescing leaf blade was characterised by low contents of chlorophyll (Chl) a and Chl b, whereas in mature leaves, the content of Chls as well as the content of total carotenoids (Car) slightly increased from basal to apical leaf part. This was reflected also in the ratio Chl (a+b)/total Car; the ratio of Chl a/b did not significantly differ between individual parts of leaf blade. Both genotypes examined differed in the character of developmental gradient observed along whole length of leaf blade. and J. Kutík ... [et al.].
Rye (Secale cereale L.) plants were treated with an ethylene releaser ethephon (2-chloroethylphosphonic acid) in concentration of 4×10-2 M. We studied electron microscopically, if and how chloroplasts interact with well-documented sites of ethylene production/binding, i.e., with endoplasmic reticulum, dictyosomes, mitochondria, plasma membrane, and tonoplast. During the sharp increase of ethylene synthesis in mesophyll cells of rye leaves, the direct local continguity of chloroplast envelope or envelope protrusions with the above mentioned cell compartments was typical. Moreover, a large number and diversity of versatile chloroplast-dictyosome associations were conspicuous, in which both the chloroplast and each cisterna of dictyosome were capable to exo/endocytosis. The dictyosomes were directed towards the chloroplasts, plasma membrane, or tonoplast both with cis-face, trans-face, or with the rim, they could change their direction or shut up the trans-face, developing simultaneously several flexible chains of vesicular dispatches among chloroplasts and some other cell compartments. This reflects interaction of protein/ethylene producing, photosynthesising, DNA containing compartments, and regulated action of lysosomal system. Structural contacts and vesicular transport among compartments of symplastic system equalises concentrations of H+, Ca2+, etc. ions, as well as provide connection with an apoplast. We propose that ethylene functions in plant mesophyll cells are both as intra/intercellular signalling substance and as phytohormone that regulates gene expression in nuclei, chloroplasts, and mitochondria in a complicated synapse-like process and causes programmed death of leaves of the main stalks of rye for the sake of promoted growth of side shoots. and T. Selga, M. Selga.
Influence of moderate chilling stress on vascular bundle sheath cell (BSC) and especially mesophyll cell (MC) chloroplasts of mature maize leaves was studied by electron microscopy and stereology. Plants of two inbred lines of maize, differing in their photosynthetic activity, and their F1 hybrids were cultivated during autumn in heated or unheated glasshouse. Generally, chilling temperatures resulted mainly in the decrease in stereological volume density (VD) of both granal and intergranal thylakoids of MC chloroplasts, while the ratio of granal to all thylakoids (granality) was less affected. The VD of peripheral reticulum and plastoglobuli usually increased after cold treatment of plants. The volume of MC chloroplasts usually increased under chilling stress, the shape of the chloroplasts changed only slightly. The ultra-structure of chloroplasts differed between individual genotypes; chilling-stressed hybrid plants showed positive heterosis particularly in the granal thylakoids' VD of MC chloroplasts. and J. Kutík ... [et al.].