Since 2002, Silver buffaloberry (Shepherdia argentea) has been introduced from North America in order to improve the fragile ecological environment in western China. To elucidate the
salt-resistance mechanism of S. argentea, we conducted a test with two-year-old seedlings subjected to 0, 200, 400, and 600 mM NaCl solutions for 30 d. The results showed that significant salt-induced suppression of plant fresh mass (FM) and stem height of S. argentea seedlings occurred only at the highest salinity level (600 mM). Leaf number, plant dry mass (DM), and chlorophyll (Chl) content declined markedly at both 400 and 600 mM. Leaf area (LA) and leaf water potential (Ψw) continuously declined with the increase of salinity. There was also a progressive and evident decrease in net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) with the increase of salinity and time. The correlation analysis indicated that PN was positively correlated with gs at all salinity levels while correlated with intercellular CO2 concentration (Ci) only at moderate salinity levels (<600 mM). Based on the initial slope of the PN/Ci curves, the estimated carboxylation efficiency (CE) was strongly inhibited at 600 mM. We confirm that S. argentea is highly tolerant to salinity. Moreover, our results show that at moderate salinity levels, salt-induced inhibition of photosynthesis is mainly attributed to the stomatal efficient closure predetermined by a low water potential in leaves; while at the high salinity levels, the inhibition is mainly due to the suppression of chloroplast capacity to fix CO2 caused by the serious decline in both CE and Chl contents. and J. Qin ... [et al.].
The present study was conducted to examine changes in photosynthetic pigment composition and functional state of the thylakoid membranes during the individual steps of preparation of samples that are intended for a separation of pigmentprotein complexes by nondenaturing polyacrylamide gel electrophoresis. The thylakoid membranes were isolated from barley leaves (Hordeum vulgare L.) grown under low irradiance (50 μmol m-2 s-1). Functional state of the thylakoid membrane preparations was evaluated by determination of the maximal photochemical efficiency of photosystem (PS) II (FV/FM) and by analysis of excitation and emission spectra of chlorophyll a (Chl a) fluorescence at 77 K. All measurements were done at three phases of preparation of the samples: (1) in the suspensions of osmotically-shocked broken chloroplasts, (2) thylakoid membranes in extraction buffer containing Tris, glycine, and glycerol and (3) thylakoid membranes solubilized with a detergent decyl-β-D-maltosid. FV/FM was reduced from 0.815 in the first step to 0.723 in the second step and to values close to zero in solubilized membranes. Pigment composition was not pronouncedly changed during preparation of the thylakoid membrane samples. Isolation of thylakoid membranes affected the efficiency of excitation energy transfer within PSII complexes only slightly. Emission and excitation fluorescence spectra of the solubilized membranes resemble spectra of trimers of PSII light-harvesting complexes (LHCII). Despite a disrupted excitation energy transfer from LHCII to PSII antenna core in solubilized membranes, energy transfer from Chl b and carotenoids to emission forms of Chl a within LHCII trimers remained effective. and V. Karlický ... [et al.].
Botanical knowledge can be directly applied especially in nature conservation and ecological restoration. Extensive field experience, good knowledge of plants and thorough theoretical background are important prerequisites. Some applications are also possible in the agricultural, forestry, pharmacy, food and textile industries. and Karel Prach.
Predace semen je strategie, kdy živočich za účelem obživy napadá a zničí mnoho semen rostlin. V tomto krátkém sdělení přibližujeme aktuální poznatky o střevlíkovitých predátorech semen po uvolnění z rostliny. Střevlíkovití brouci zpravidla preferují semena odpovídající velikosti jejich těla, výběr druhů preferovaných semen je však pro daný druh střevlíka typický a během sezony se nemění. Během sezony značně kolísá množství spotřebovaných semen, za optimálních podmínek vysoké hojnosti a aktivity brouků může být denně zničeno až 1000 semen na ploše 1 m2. Střevlíkovití přitom preferují semena hvězdnicovitých rostlin (Asteraceae), jako jsou pampelišky (Taraxacum sect. Ruderalia) nebo pcháč oset (Cirsium arvense), dále semena brukvovitých (Brassicaceae), jako je kokoška pastuší tobolka (Capsella bursa-pastoris). Střevlíkovití tak přispívají k udržení biologické rovnováhy., Seed predation is a strategy where an animal attacks and kills the seeds of plants. In this contribution we report on the latest knowledge on carabid beetles (Carabidae) feeding on seeds after dispersal from the plant. In general, carabid beetles prefer seeds of appropriate size to their body size, but the selection of seed species is species-specific and remains stable across the season. The consumption considerably varies throughout the year, and under optimal conditions the carabid beetles may destroy up to 1000 seeds per 1 m2. Carabid beetles prefer seeds of Asteraceae, such as Dandelion (Taraxacum) or Canadian Thistle (Cirsium arvense), and of Brassicaceae, such as the Shepherd’s Purse (Capsella bursa-pastoris). In this way the carabid beetles contribute to the balance in ecosystems., and Pavel Saska, Alois Honěk, Zdenka Martinková.
Small molecules that regulate the cell division cycle are a joint research project of the CAS Institute of Experimental Botany and Palacký University’s Faculty of Science. An interview with Professor Miroslav Strnad, head of the Laboratory of Growth Regulations, describes the significance of this joint project. The laboratory concentrates its research on small molecules that regulate cell division cycle, proliferation and growth of both plant and animal cells. Cytokinins and cytokinin-derived purine inhibitors of cyclindependent kinases are the most intensively studied compounds. The multidisciplinary research team is composed of experienced plant physiologists, biochemists and organic and analytical chemists. Many students are involved in the research phase during their pre-graduate and postgraduate studies in botany, analytical and organic chemistry, biochemistry or medicinal biology. Several research projects are in progress in collaboration with international partners (University of Berlin; Swedish University of Agricultural Sciences; University of Natal Pietermaritzburg, South Africa and the Vienna Medical University. and Marina Hužvárová.
The extrinsic proteins of photosystem II in plants (PsbO, PsbP and PsbQ) are known to be targets of stress. In previous work, differential regulation of hypothetical isoforms of these proteins was observed in Nicotiana benthamiana upon viral infection. Each of these proteins is encoded by a multigene family in this species: there are at least four genes encoding PsbO and PsbP and two encoding PsbQ. The results of structural and functional analyses suggest that PsbO and PsbP isoforms could show differences in activity, based on significant substitutions in their primary structure. Two psbQ sequences were isolated which encode identical mature proteins. and M. I. Pérez-Bueno ... [et al.].
Přijetím konceptu deskové tektoniky v 60. letech 20. století se od základu změnil náhled na původ latinskoamerické flóry. Zjistilo se, že dnešní kontinent Jižní Ameriky byl před 100 miliony lety součástí pradávného kontinentu Gondwany a její jednotné flóry. Tento poznatek vedl k interpretaci vzniku disjunktních areálů taxonů rozšířených v Jižní Americe a na ostatních částech bývalé Gondwany v důsledku rozpadu dřívějšího kontinuálního areálu výskytu. Po následném oddělení kontinentu Jižní Ameriky od Gondwany přibližně před 100 miliony lety se předpokládalo, že se zde vegetace vyvíjela izolovaně až do vytvoření Panamské šíje před 3 miliony lety. Novější výzkumy a použití tzv. molekulárních hodin však ukazují, že výměna bioty mezi Jižní Amerikou a sousedícími kontinenty v určitých obdobích ještě před uzavřením Panamské šíje přeci jen probíhala., The concept of plate tectonics accepted during the 20th century fundamentally altered general opinion on the origin of Latin American flora. South America formed a part of the ancient continent Gondwana, which had a unique flora. The separation of South America finished about 100 million years ago led to the isolation of its flora until the formation of the Isthmus of Panama about three million years ago. The current disjunctions of widely distributed tropical taxa originated after this disruption. However, recent studies based on molecular clock approaches show that the migration of biota between South America and the rest of the world occurred repeatedly even before the closure of the Isthmus., and Anna Potůčková, Daniel Stančík.
Pro odhad stáří jednotlivých vývojových linií latinskoamerické flóry se dnes využívají také tzv. molekulární hodiny. Výsledky jejich aplikace ukazují, že se řada prvků současné flóry dostala do Latinské Ameriky až po rozpadu prakontinentu Gondawana, tzn. jsou mladšího stáří než by odpovídalo době rozpadu Gondwany. Do Latinské Ameriky se mohly rozšířit dvěma různými mechanismy: migrací rostlin přes pevninu a nebo disperzí diaspor na dlouhou vzdálenost přes oceány. Důkazem migrace tropických čeledí přes kontinenty je i řada fosilních nálezů, které mohou také posloužit jako druhý nezávislý zdroj datování jejich původu., So called molecular clocks are nowadays used to estimate the age of individual lineages of Latin American flora. The results of their application show that a number of elements of current flora came to Latin America after the collapse of the ancient continent of Gondwana. This could be explained by two different mechanisms: by migration of plants across the land or by dispersion of their diasporas across the oceans. The amount of fossils proving migration of tropical families across continents is often used as the second, independent source for dating their origin., and Anna Potůčková, Daniel Stančík.