The toxic effect of the cultivation medium of plants infected with tobacco mosaic virus

P?i studiu klí?ních rostlin raj?at pěstovaných ve vodních kulturách bylo zji?těmo, ?e ko?eny rostlin infikovaných TMV vylu?ují do kultia?ního média látky, které p?sobí toxicky na neinfikované rostliny rostoucí spole?ně v tém?e médiu.     

Flechtensystematische Studien VI. Die GattungSagiolechia Massal.

Eine taxonomische Studie über die GattungSagiolechia Massal. als wieter Teil einer Revision der FamilieGyalectaceae sensuZahlbruckner wird vorgelegt.     

Biomass partitioning in twoCalamagrostis villosa stands on deforested sites

Calamagrostis villosa stands occurring in areas deforested by air-pollution impact in the Moravian-Silesian Beskydy Mountains were characterized by a high dry mass of total underground biomass (3 300 g. m^?2—the slope site, 2 850 g. m^?2—the flat site). The percentage of living roots and rhizomes in total underground biomass was very high (about 70%). The total aboveground biomass was respectively, 321 g.m^?2 (the slope site) and 726 g. m^?2 (the flat site). In unstabilized habitats on steep slope, the higher plant biomass produced was allocated to a more developed root system.     

Stand microclimate and physiological activity of tree leaves in an oak-hornbeam forest

Summary In an uneven-aged, multi-species oak-hornbeam forest at Báb, SW Slovakia (former IBP Forest Research Site), a series of micrometeorological and ecophysiological measurements started in 1985. The aims of the work are to improve understanding of physiological processes (photosynthesis, respiration, and transpiration) of adult trees and stand microclimate, to collect data for simulation of the canopy (stand) photosynthesis and for ecological synthesis of the functioning of the forest ecosystem. In this paper, photosynthetically active radiation (PAR), air temperature (AT) and relative humidity (RH), wind speed (WS), and CO₂ concentration ([CO₂]) in and above the forest are characterized for the fully leaved season, using diurnal courses, vertical profiles and isodiagrams (isopleths). Approximately 50% of incident PAR was absorbed by the upper 4–5 m layer of leaves and only approximately 5% or less penetrated to the forest floor. Vertical gradients of AT and RH were generally low, but large differences in diurnal ranges of AT and RH were observed between vertical levels. The upper leaf canopy greatly reduced WS, and at a height of about 14 m above the ground it was close to zero. The highest diurnal [CO₂] maximum and variations occurred at 1 m above the ground, and the lowest above the forest. In good light conditions in the forest, the entire leaf canopy (overstorey and understorey canopy) is a large sink of CO₂. At night the forest stand is a source of CO₂, the largest internal source being the soil and forest floor.     

A Photorespiratory Mutant of Chlamydomonas reinhardtii

A mutant strain of Chlamydomonas reinhardtii, designated 18-7F, has been isolated and characterized. 18-7F requires a high CO₂ concentration for photoautrophic growth in spite of the apparent induction of a functional CO₂ concentrating mechanism in air-adapted cells. In 2% O₂ the photosynthetic characteristics of 18-7F and wild type are similar. In 21% O₂, photosynthetic O₂ evolution is severely inhibited in the mutant by preillumination in limiting CO₂, although the apparent photosynthetic affinity for inorganic carbon is similar in preilluminated cells and in cells incubated in the dark prior to O₂ evolution measurements. Net CO₂ uptake is also inhibited when the cells are exposed to air (21% O₂, 0.035% CO₂, balance N₂) for longer than a few minutes. [¹⁴C]Phosphoglycolate accumulates within 5 minutes of photosynthetic ¹⁴CO₂ fixation in cells of 18-7F. Phosphoglycolate does not accumulate in wild type. Phosphoglycolate phosphatase activity in extracts from air-adapted cells of 18-7F is 10 to 20% of that in wild-type Chlamydomonas. The activity of phosphoglycolate phosphatase in heterozygous diploids is intermediate between that of homozygous mutant and wild-type diploids. It was concluded that the high-CO₂ requiring phenotype in 18-7F results from a phosphoglycolate phosphatase deficiency. Genetic analyses indicated that this deficiency results from a single-gene, nuclear mutation. We have named the locus pgp-1.     

Stream vegetation in different landscape types

A methodology is proposed for assessing the ecological value of streams in the catchment of the Moravská Dyje River. It is concluded that by using a wide range of parameters that a more objective assessment is achieved than if only one were used. The landscape of the catchment studied contains excessive amounts of nutrients and, in comparison to its natural state, has become too uniform.     

Partial auxin deprivation affects endogenous cytokinins in an auxin-dependent,cytokinin-independent tobacco cell strain

The dynamics of individual endogenous cytokinins within the growth cycle (subculture interval) of an auxin-dependent and cytokinin-independent cell suspension culture ofNicotiana tabacum L. (strain VBI-0) were determined using high performance liquid chromatography and radioimmunoassay. In cells grown at an optimum auxin concentration the transient maxima of N⁶-(²-isopentenyl)adenine and N⁶-(²-isopentenyl)-adenosine correlated with the onset of cell division. Cultivation of the cells in a partially auxin-deprived medium resulted in ca. tenfold increase of all endogenous cytokinins. A very distinct maximum of N⁶-(²-sopentenyl) adenine appeared at the beginning of subculture. This indicates that a lack of auxin induced an accumulation of cytokinins predominantly in the form of the free bases, which are physiologically more active than the corresponding ribosides.Abbreviations iP N⁶-(²-isopentenyl)adenine - [9R]iP N⁶-(²-isopentenyl)adenosine - t-Z trans-zeatin - t-[9R]Z trans-zeatin riboside - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - f.w. fresh weight - SBI subculture interval - C complete medium - PAD partially auxin-deprived medium - RP-HPLC reverse phase high performance liquid chromatography - RIA radioimmunoassay - PAL L-phenylalanine ammonia lyase     

Ordovician (Dobrotivá Formation) ostracodes and trilobites from Ejpovice (Bohemia) and their relations to faunas of northern and western Europe

For the first time a complete ostracode and trilobite fauna is described from the Dobrovitá Formation (Ordovician) of Perunica. In contrast to the trilobite fauna the ostracode fauna evidences close relations to both Armorica and Baltica. The trilobite fauna comprises 11 species out of 11 genera, the ostracode fauna comprises 15 (5 new) species out of 15 (1 new) genera.