Hvězdoše patří k nejběžnějším a přitom nejvíce přehlíženým vodním rostlinám naší květeny. Jsou charakterizovány na jedné straně celkovou redukcí tělní stavby, na druhé straně vysokou měrou fenotypové plasticity – schopností pružně reagovat na změny prostředí změnou habitu. Kvůli těmto vlastnostem patří hvězdoše mezi determinačně obtížné skupiny. Překvapivě však existuje u hvězdošů pozoruhodné množství různých opylovacích způsobů: dokáží se opylovat na vzduchu, po vodní hladině i pod vodou. Kombinace všech těchto tří způsobů opylení není známa u žádných jiných rostlin. Všechny opylovací systémy se pak u hvězdošů kombinují s ojedinělými a kuriózními způsoby samoopylení., Water-starworts (Callitriche) are some of the most common and yet largely overlooked aquatic plants in European flora. They are characterized by overall reduction of the plant body and also exhibit an extraordinary phenotypic plasticity in response to environmental changes, which makes the starwort species very difficult to determine. It is the only genus known to possess all three types of pollination: by air, on the water surface and under water, in addition to some unique self-fertilization mechanisms., and Jan Prančl.
In the CR located on the bio-geographical crossroads of Central Europe, several vegetation types reach their distribution limit here, whereas only three vegetation types and complexes unique or significantly concentrated here are identified: grasslands in the White Carpathian Mts. (the world’s highest number of vascular plant species per certain areas smaller than 50 m2); sandstone pseudokarst landscapes (sharply contrasting vegetation at very short distances); fishponds (specific vegetation especially on their exposed bottoms when drained). and Milan Chytrý, Handrij Härtel, Kateřina Šumberová.
The aim of this study was to assess the impact of the mitochondrial alternative oxidase (AOX) pathway on energy metabolism in chloroplasts, and evaluate the importance of the AOX in alleviating drought-induced photoinhibition in pepper (Capsicum annuum L.). Inhibition of AOX pathway decreased photosynthesis and increased thermal energy dissipation in plants under normal conditions. It indicated that AOX pathway could influence chloroplast energy metabolism. Drought reduced carbon assimilation. Photoinhibition was caused by excess of absorbed light energy in spite of the increase of thermal energy dissipation and cyclic electron flow around PSI (CEF-PSI). Upregulation of AOX pathway in leaves experiencing drought would play a critical role in protection against photoinhibition by optimization of carbon assimilation and PSII function, which would avoid over-reduction of photosynthetic electron transport chain. However, inhibition of AOX pathway could be compensated by increasing the thermal energy dissipation and CEF-PSI under drought stress, and the compensation of CEF-PSI was especially significant., W. H. Hu, X. H. Yan, Y. He, X. L. Ye., and Obsahuje bibliografii
The present work showed that spider mite-infested leaves placed in the light were more attractive to predatory mites than the infested leaves placed in the dark; furthermore, an increase in the light intensity enhanced this attractiveness. However, the increase of the light intensity did not change the attractiveness of the uninfested leaves to predatory mites. The capacity of cyanide-resistant respiration and the photosynthetic rates of both the infested and uninfested leaves increased with increasing light intensities, whereas the photosystem (PS) II chlorophyll (Chl) fluorescence decreased. The increase of the capacity of cyanide-resistant respiration in the infested leaves was more dramatic than that in the uninfested leaves, whereas the values of photosynthetic rates and Chl fluorescence were lower in the infested leaves than those in the uninfested leaves. Treatment of the infested and uninfested leaves with 1 mM salicylhydroxamic acid (SHAM, an inhibitor of cyanide-resistant respiration) decreased photosynthetic rates and caused further reductions in PSII fluorescence, especially under a higher light intensity. In contrast, the effects of SHAM on PSII fluorescence parameters and photosynthetic rates of the infested leaves were more dramatic than on those of the uninfested leaves. The treatment with SHAM did not significantly change the attractiveness of the infested or uninfested leaves to the predatory mites under all of the light intensities tested. These results indicated that cyanide-resistant respiration was not directly associated with the light-induced attraction of predators to plants, but it could play a role in the protection of photosynthesis. Such role might become relatively more important when photosynthesis is impaired by herbivores infestation. and H. Q. Feng ... [et al.].
1_The young larvae of insects living on dry food produce large amounts of water by the metabolic combustion of dietary lipids. The metabolic production of water needed for larval growth, previously known as hypermetabolic responses to juvenile hormone (JH), is associated with a 10- to 20-fold increase in the rate of O2 consumption (10,000 µl O2/g/h in contrast to the usual rate of 500 µl O2/g/h). Growing and moulting larvae are naturally hypermetabolic due to the endogenous release of JH from the corpora allata. At the last, larval-pupal or larval-adult moult there is no JH and as a consequence the metabolic rate is much lower and the dietary lipid is not metabolized to produce water but stored in the fat body. At this developmental stage, however, a hypermetabolic response can be induced by the exogenous treatment of the last larval instars with a synthetic JH analogue. In D. vulpinus, the JH-treated hypermetabolic larvae survive for several weeks without moulting or pupating. In T. castaneum and G. mellonella, the JH-treated hypermetabolic larvae moult several times but do not pupate. All these larvae consume dry food and the hypermetabolic response to JH is considered to be a secondary feature of a hormone, which is produced by some subordinated endocrine organ., 2_The organ is most probably the controversial prothoracic gland (PG), which is a typical larval endocrine gland that only functions when JH is present. According to our hypothesis, PG activated by JH (not by a hypothetical PTTH) releases an adipokinetic superhormone, which initiates the conversion of dietary lipid into metabolic water. This type of metabolic combustion of dietary lipid produces large quantities of endothermic energy, which is dissipated by the larvae in the form of heat. Thermovision imaging revealed that the body of hypermetabolic larvae of G. mellonella can be as hot as 43°C or more. In contrast, the temperature of "cold" normal last instar larvae did not differ significantly from that of their environment. It is highly likely that thermovision will facilitate the elucidation of the currently poorly understood hormonal mechanisms that initiate the production of metabolic water essential for the survival of insects that live in absolutely dry conditions., Karel Sláma, Jan Lukáš., and Obsahuje seznam literatury
Diglyphus isaea Walker (Hymenoptera: Eulophidae) is an important ectoparasitic wasp of many leaf miners. Ability of D. isaea to find hosts placed in artificial mines and for its larvae to pupate when the larva is not in a mine was studied. Artificial mines consisted of slits cut in index card sandwiched between two cover slips. Almost 80% of the neonate larvae of D. isaea located host larvae in artificial mines compared to only 50% of those not in a mine. Mature larvae removed from mines did not construct normal pupal chambers. Nonetheless, they pupated and emerged successfully. Larvae of Liriomyza sativae Blanchard (Diptera: Agromyzidae) in mines are more likely to be attacked than those not in mines. Moreover, when close to a host larva this parasitoid can use vibrational cues to locate the larva in a mine. In addition, this parasitoid also did not always use volatile and gustatory cues for short range location of hosts. However, adult females of D. isaea more quickly located L. sativae larvae in the presence of the odour of juice extracted from an uninfested host plant. We conclude by proposing that the host mine is the medium by which the vibrations generated by the host larva are transmitted, which are probably the most important cue used by female D. isaea searching for hosts. That is this parasitoid first perceives mines not host larvae. These results will be helpful for developing techniques for the mass rearing of D. isaea in the future., De Yu Zou, Hong Yin Chen, Li Sheng Zhang., and Obsahuje seznam literatury
Effects of elevated root-zone (RZ) CO2 concentration (RZ [CO2]) and RZ temperature (RZT) on photosynthesis, productivity, nitrate (NO3-), total reduced nitrogen (TRN), total leaf soluble and Rubisco proteins were studied in aeroponically grown lettuce plants in a tropical greenhouse. Three weeks after transplanting, four different RZ [CO2] concentrations (ambient, 360 ppm, and elevated concentrations of 2,000; 10,000; and 50,000 ppm) were imposed on plants at 20°C-RZT or ambient(A)-RZT (24-38°C). Elevated RZ [CO2] resulted in significantly higher light-saturated net photosynthetic rate, but lower light-saturated stomatal conductance. Higher elevated RZ [CO2] also protected plants from both chronic and dynamic photoinhibition (measured by chlorophyll fluorescence Fv/Fm ratio) and reduced leaf water loss. Under each RZ [CO2], all these variables were significantly higher in 20°C-RZT plants than in A-RZT plants. All plants accumulated more biomass at elevated RZ [CO2] than at ambient RZ [CO2]. Greater increases of biomass in roots than in shoots were manifested by lower shoot/root ratios at elevated RZ [CO2]. Although the total biomass was higher at 20°C-RZT, the increase in biomass under elevated RZ [CO2] was greater at A-RZT. Shoot NO3- and TRN concentrations, total leaf soluble and Rubisco protein concentrations were higher in all elevated RZ [CO2] plants than in plants under ambient RZ [CO2] at both RZTs. Under each RZ [CO2], total leaf soluble and Rubisco protein concentrations were significantly higher at 20°C-RZT than at A-RZT. Our results demonstrated that increased P Nmax and productivity under elevated [CO2] was partially due to the alleviation of midday water loss, both dynamic and chronic photoinhibition as well as higher turnover of Calvin cycle with higher Rubisco proteins. and J. He, L. Qin, S. K. Lee.
Botanická zahrada v Rio de Janeiru je zajímavým východiskem k pozorování bromeliovitých rostlin. Nachází se v oblasti obzvláště bohaté na zástupce čeledi Bromeliaceae. Zvláštní kapitola je věnována robustním druhům rodu Alcantarea a jejich ekologii. Je zmíněn slavný zahradní architekt Roberto Burle Marx, který uvedl druh Alcantarea imperialis do svých věhlasných zahradních aranžmá., The Botanical Garden of Rio de Janeiro is an interesting starting point for observation of bromeliads. It is located in an area particularly rich in species of the family Bromeliaceae. An emphasis is given to robust species of the genus Alcantarea and their ecology. Roberto Burle Marx, a famous garden and park designer, is mentioned because he introduced the species A. imperialis in his well-known garden arrangements., and Miloslav Studnička.
The flora of the CR harbours 48 endemic (sub)species of vascular plants (plus 26 taxa considered as near-endemic). Most of them occur above the timberline in the High Sudetes Mts. while others are restricted to lowland habitats with specific edaphic or topographic features (serpentine outcrops, calcareous fens, rocks in steep river valleys). Apomicts clearly prevail (49 taxa, especially Hieracium and Sorbus). All endemics are evolutionarily young (neoendemics) and their origin is mostly associated with the Quaternary climatic oscillations. and Jan Suda, Zdeněk Kaplan.