Hořec hořepník (Gentiana pneumonanthe) se vyskytuje v mírném pásu Evropy a jeho areál zasahuje až do oblasti jihozápadní Sibiře. Ve střední Evropě najdeme hořepník na nehnojených, střídavě vlhkých bezkolencových loukách a extenzivních pastvinách. V ČR i řadě okolních zemí je hořec hořepník považován za vzácný a ohrožený druh, a to přestože jde o vytrvalý, dlouhověký druh, který produkuje velký počet semen. Podobně jako řada dalších druhů se stal obětí odvodnění a radikálních změn ve způsobu obhospodařování krajiny. Pro zachování životaschopné populace hořce hořepníku je hlavní klíčení a přežívání semenáčků, které úspěšně probíhá pouze na ploškách s obnaženým půdním povrchem (gaps). Optimálně načasované kosení, pastva či nejlépe jejich kombinace jsou vhodným managementem hořepníkových lokalit a nadějí i pro kriticky ohroženého modráska hořcového (Phengaris alcon, dříve Maculinea alcon). Tento druh využívá hořce hořepníky u nás coby hlavní živnou rostlinu a dostatečně početná populace hořepníku je považována za jednu z hlavních podmínek výskytu modráska., Gentiana pneumonanthe occurs in the temperate zone of Europe, with its range extending to southwest Siberia. In central Europe, the species grows in oligotrophic wet meadows (Molinion) and extensive pastures. Plants are perennial, long-lived and produce many seeds. It is a rare and endangered species of the Czech flora and floras of many neighbouring countries; drainage of its sites and abandonment of traditional management practices are the major threats. Germination and seedling survival (the crucial phases of the species life cycle) are successful only in gaps with bare soil. Proper timing of mowing and grazing, or preferably their combination, are necessary for effective species conservation. They also give a chance to the Blue Alcon (Phengaris alcon, formerly Maculinea alcon), a monophagous butterfly feeding on Marsh Gentian. The Blue Alcon usually occurs only in large populations of its food-plant., Zdenka Křenová., and Obsahuje seznam literatury
Hořec panonský (Gentiana pannonica) bývá označována za erbovní rostlinu Šumavy, která je jedinou přirozenou oblastí výskytu tohoto druhu mimo Alpy. V případě Šumavy byl přirozený výskyt omezen na maloplošná refugia přirozeného bezlesí - kary ledovcových jezer, okraje slatí a horských potoků. Na ostatní lokality se hořec rozšířil až po kolonizaci Šumavy lidmi. Na některá místa si horalé hořce pravděpodobně přesadili či vyseli. Další vhodné lokality vzniklé odlesněním části šumavských plání hořec osídlil spontánně. Dlouhodobé přežívání hořce panonského je pojištěno klonálním růstem, díky kterému na některých lokalitách vytváří rozsáhlé polykormony. Květy opylují čmeláci, ale jsou také schopné samoopylení. Křídlatá semena, která mohou za pomoci větru putovat po sněhové krustě či plavat ve vodě, například z tajícího sněhu, úspěšně klíčí v gapech. Podobně jako i další druhy se silnými kořeny a oddenky byl h. panonský využíván k domácí výrobě hořcové pálenky a žaludečních likérů. Druhům hořec žlutý (G. lutea), h. nachový (G. purpurea) a h. tečkovaný (G. punctata) je stručně věnován závěr článku., Hungarian Gentian (Gentiana pannonica) has been considered the heraldic plant of the Šumava Mts., its only natural distribution outside the Alps. The species originally inhabited only small non-forest refugia but spread into other sites after human colonization of the Šumava Mts. It is likely that the species was deliberately transplanted or sown in suitable sites close to the settlements. Some habitats were also colonized spontaneously. Hungarian Gentian is a long-lived perennial with profound clonal propagation. Flowers are pollinated by bumble-bees, but self-pollination is also possible. Seeds successfully germinate in gaps. In this article, Yellow Gentian (G. lutea), Purple Gentian (G. purpurea) and Spotted Gentian (G. punctata) are also briefly discussed., and Zdenka Křenová.
Poslední díl seriálu seznamuje se dvěma opravdu blankytně modrými hořci. Hořec brvitý (Gentianopsis ciliata) má těžiště rozšíření v prostoru střední Evropy, Alp a Balkánu. Nedávné studie potvrzují, že jde o vytrvalý, relativně krátkověký druh. Pozoruhodná je jeho schopnost vegetativního rozrůstání z adventivních pupenů. Ty dávají vzniknout novým nadzemním lodyhám, které jsou neodlišitelné od samostatných oddělených rostlin. Experimentální studie ukazují, že je velmi obtížné stanovit optimální obhospodařování jeho lokalit. Seč v tradičních termínech (červen) výrazně ničí jeho lodyhy. Stejně tak je druh náchylný na zarůstání lokalit křovinami a nedostatek prostoru (mezer v porostu, tzv. gapů) ke klíčení. Hořec křížatý (Gentiana crutiata) roste roztroušeně téměř v celé Evropě a západní Asii. Jde o vytrvalý druh. Jeho dlouhodobé přežívání na lokalitě je však závislé zamezení zarůstání a možnosti vyklíčení semen na obnažených, disturbovaných plochách. Často roste, obdobně jako další druhy hořců a hořečků, na místech, kde byla disturbance prováděná pasenými zvířaty nahrazena aktivitami moderního člověka (jízda na koních, motorkách, čtyřkolkách, též ve vojenských újezdech na dopadových plochách či tzv. tankodromech). Hořce a hořečky jsou přírodním a kulturním dědictvím naší krajiny. Cílem seriálu bylo ukázat, že jako takové má smysl jejich biotopy chránit a obhospodařovat., The last part of our series introduces two species. The Fringed Gentian (Gentianopsis ciliata) occurs in Central Europe, in the Alps and in the Balkans. It is a perennial but relatively short-lived species, remarkable for vegetative propagation from adventitious buds. Tailoring management of its sites is very difficult – traditional mowing in June destroys many of the stems, but the inhibition of succession and the creation of gaps are essential for successful propagation of the species. The perennial species Cross Gentian (Gentiana cruciata), scattered across Europe and western Asia, occurs in places where traditional disturbances by grazing animals are often replaced by human leisure activities or military training. The inhibition of shrub succession and small-scale soil disturbances are essential for survival of this species. The main aim of our series was to justify the protection of Gentians and suggest appropriate management of their habitats., and Zdenka Křenová, Jiří Brabec.
Hlavním druhem posledního dílu horečkové části seriálu je hořeček nahořklý. Jde o široce rozšířený druh - Evropa, severní Asie až po střední Sibiř, Dálný východ, Severní Amerika. Počet lokalit a velikost populací tohoto druhu však v ČR v posledních dekádách dramaticky poklesl. V současné době je prokázán ze 71 lokalit (70 lokalit G. amarella subsp. amarella a jedna lokalita G. amarella subsp. lingulata). Z ČR je známo též několik horečkových kříženců. Do současnosti se zachovaly populace dvou z nich. U hořečků je známé synchronizované kolísání velikosti populací. V ČR lze tento jev dokumentovat na dvou druzích přežívajících dosud ve více populacích (G. praecox subsp. bohemica a G. amarella). Příčiny synchronizace nejsou známy. Jednou z hypotéz je masivní klíčení, růst a v dalším roce kvetení hořečků v mezerách nárazově vytvořených v jinak relativně zapojeném travním porostu. Synchronizované vytvoření mezer v porostu pak může být způsobeno přísuškem během vegetační sezóny., G. amarella is a widely distributed species (Europe, northern Asia to Central Siberia, the Far East and North America); however, the number of its sites and population size have decreased dramatically in the last few decades in the Czech Republic. At present, the species is documented from 71 sites here (70 sites of G. a. subsp. amarella, one site of G. a. subsp. lingulata). Several hybrids of Gentianella species are also known from the Czech Republic (two of them have survived so far). A synchronized inter-annual fluctuation in population size is documented for G. praecox subsp. bohemica and G. amarella in the Czech Republic. The reasons behind, however, remain unclear. Massive establishment, survival and flowering in the year following the creation of gaps in vegetation have been suggested as an explanation. Synchronized occurrence of gaps may be caused by a dry period during the growing season., Jiří Brabec., and Obsahuje seznam literatury
The influence of arbuscular mycorrhizal (AM) fungus Glomus deserticola (Trappe and John) on plant growth, nutrition, flower yield, water relations, chlorophyll (Chl) contents and water-use efficiency (WUE) of snapdragon (Antirhinum majus cv. butterfly) plants were studied in potted culture under well-watered (WW) and water-stress (WS) conditions. The imposed water stress condition significantly reduced all growth parameters, nutrient contents, flower yield, water relations, and Chl pigment content and increased the electrolyte leakage of the plants comparing to those of nonstressed plants. Regardless of the WS level, the mycorrhizal snapdragon plants had significantly higher shoot and root dry mass (DM), WUE, flower yield, nutrient (P, N, K, Mg, and Ca) and Chl contents than those nonmycorrhizal plants grown both under WW or WS conditions. Under WS conditions, the AM colonization had greatly improved the leaf water potential (Ψw), leaf relative water content (RWC) and reduced the leaf electrolyte leakage (EL) of the plants. Although the WS conditions had markedly increased the proline content of the leaves, this increase was significantly higher in nonmycorrhizal than in mycorrhizal plants. This suggests that AM colonization enhances the host plant WS tolerance. Values of benefit and potential dry matter for AM-root associations were highest when plants were stressed and reduced under WW conditions. As a result, the snapdragon plants showed a high degree of dependency on AM fungi which improve plant growth, flower yield, water relations particularly under WS conditions, and these improvements were increased as WS level had increased. This study confirms that AM colonization can mitigate the deleterious effect of water stress on growth and flower yield of the snapdragon ornamental plant., A. A. Asrar, G. M. Abdel-Fattah, K. M. Elhindi., and Obsahuje bibliografii
The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ‘P360’, and ‘PS1313’, respectively. Plants were grown hydroponically and supplied with two nutrient solutions - a nonsalinized control and a salinized solution which contained 40 mmol L-1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the
PN and gs reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na+ and Cl- in the leaf tissue and PN. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and PN. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance., Y. Rouphael ... [et al.]., and Obsahuje bibliografii
To investigate the effect of low CO2 on the expression and activity of ferredoxin-NADP+ oxidoreductase (FNR) and this enzyme-mediated cyclic electron flow around photosystem I (cyclic PSI), the activity staining, immunoblotting and initial rate of P700 + reduction were measured in high- or low-CO2-grown (H or L)-cells of wild-type Synechocystis sp. strain PCC 6803 (WT) and its ΔndhB mutant (M55). Major results were depicted as follows. (1) The protein levels and activity of FNR were remarkably stimulated in L-cells of both WT and M55 relative to that in their H-cells. (2) The rate of cyclic PSI was significantly increased in L-cells of WT, not M55, when compared to that in respective H-cells. (3) N-ethylmaleimide, an inhibitor of FNR, partially inhibited the increase in the rate of cyclic PSI induced by low CO2 in both WT and M55. These findings indicated that low CO2 enhanced the expression and activity of FNR and the cyclic PSI mediated by FNR. The contribution of FNR to cyclic PSI is shortly discussed. and Y. R. Liu, W. M. Ma, H. L. Mi.
In the terrestrial bromeliad, Puya floccosa, a value of carbon isotopic composition (δ13C) of -22‰ has been previously reported, suggesting the operation of weak and/or intermediate (C3-CAM) crassulacean acid metabolism (CAM). In order to characterize the operation of CAM in P. floccosa and its possible induction by drought, plants were grown in Caracas and subjected to four independent drought cycles. Additionally, since plants of this species grow in Venezuela in a large range of elevations, leaf samples were collected at elevations ranging from 725 to 2,100 m a.s.l. in the Venezuelan Andes and the Coastal Range, in order to evaluate the effect of elevation on CAM performance. Even though nocturnal acid accumulation occurred in both watered and droughted plants, mean ΔH+ was higher in droughted than watered plants [ΔH+ = 60.17.5 and 22.9 ± 5.2 μmol g-1(FM), respectively]. The majority of plants from all the natural populations sampled had low values of δ13C not differing significantly from those of C3 plants collected as standards and δ13C did not change with elevation. We conclude that P. floccosa is capable of a weak CAM activity, with a large variability among populations and drought experiments probably due to local and temporal differences in microclimatic variables and drought stress; elevation bears no influence on values of δ13C in this species. and A. Herrera ... [et al.].
Predicted future climatic changes for the Mediterranean region give additional importance to the study of photooxidative stress in local economic species subjected to combined drought and
high-temperature conditions. Under this context, the impact of these stresses on photosynthesis, energy partitioning, and membrane lipids, as well as the potential ability to attenuate oxidative damage, were investigated in Ceratonia siliqua L. Two thermal regimes (LT: 25/18°C; HT: 32/21°C) and three soil water conditions (control, water stress, and rewetting) were considered. HT exacerbated the adverse effects of water shortage on photosynthetic rates (PN) and PSII function. The decrease in PN was 33% at LT whereas at HT it was 84%. In spite of this, the electron transport rate (ETR) was not affected, which points to an increased allocation of reductants to sinks other than CO2 assimilation. Under LT conditions, water stress had no significant effects on yield of PSII photochemistry (ΦPSII) and yields of regulated (ΦNPQ) and nonregulated (ΦNO) energy dissipation. Conversely, drought induced a significant decrease of ΦPSII and a concomitant increase of ΦNO in HT plants, thereby favouring the overproduction of reactive oxygen species (ROS). Moreover, signs of lipid peroxidation damage were detected in HT plants, in which drought caused an increase of 40% in malondialdehyde (MDA) content. Concurrently, a marked increase in proline content was observed, while the activities of catalase (CAT) and ascorbate peroxidase (APX) were unaffected. Despite the generation of a moderate oxidative stress response, C. siliqua revealed a great capability for photosynthetic recovery 36 h after rewatering, which suggests that the species can cope with predicted climate change. and M. L. Osório ... [et al.].