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.
Současná diverzita tropické flóry a bioty Latinské Ameriky je výsledkem řady historických událostí, ke kterým došlo během jejího dlouhého vývoje. Výskyt stejných či příbuzných čeledí, rodů nebo druhů v oblastech a na kontinentech představujících součásti někdejšího prakontinentu Gondwana jsou výsledkem působení tří mechanismů: rozpadu souvislého areálu výskytu (vikariance) na území někdejší Gondwany, migrací rostlin přes kontinenty severní polokoule a disperzí přes oceány. Při mezikontinentálním rozšíření řady čeledí však často nehrál roli jen jeden z výše uvedených mechanismů, ale často šlo o jejich kombinace. Tím se stává studium historie různých taxonů komplikovanější. K jejímu odhalení je potřeba mít jasnou představu o stáří jejich jednotlivých vývojových linií, umožňující správnou interpretaci působení konkrétního mechanismu na jejich dnešní rozšíření a diverzitu., The tropical flora and biota of Latin America was influenced during its long history by several events that led to their current diversity and disjunct distribution. Three mechanisms have been proposed to explain the occurrence of the same or closely related families, genera and/or species among fragments of former Gondwana: vicariance, migration of plants across the continents and long distance dispersion. Recent intercontinental distribution of several taxa is commonly a result of their combination. Good knowledge of the age of principal lineages is needed for the correct interpretation of the effect of these mechanisms on the distribution and diversity of the investigated lineages., and Anna Potůčková, Daniel Stančík.
A portable open gas-exchange system (Li-6400, Li-Cor, Inc., Lincoln, NE, USA) has been widely used for the measurement of net gas exchanges and calibration/parameterization of leaf models. Measurement errors due to diffusive leakage rates of water vapor (LW) and CO2 (LC) between inside and outside of the leaf chamber, and the inward dark transpiration rate (DW) and dark respiration rate (DC) released from the leaf under the gasket, can be significant. Rigorous model-based approaches were developed for estimating leakage coefficients of water vapor (KW) and CO2 (KC) and correcting for the combination of these errors. Models were based on mass balance equations and the Dusty Gas Model for a ternary gas mixture of water vapor, CO2, and dry air. Experiments were conducted using two Li-6400 systems with potato and soybean leaves. Results indicated that models were reliable for estimating KW and KC, and the values varied with instrument, chamber size, gasket condition, and leaf structure. A thermally killed leaf should be used for this determination. Measurement error effects on parameterization of the Farquhar et al. (1980) model as determined by PN/C i curves were substantial and each parameter had its own sensitivity to measurement errors. Results also indicated that all four error sources should be accounted for when correcting measurements., Q. Wang ... [et al.]., and Obsahuje bibliografii a dodatky
Net photosynthetic rate (PN) measured at elevated CO2 concentration (Ce), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and nitrogen (N) content in rice leaves decreased significantly after exposure to long term Ce. The reduction in PN, Rubisco, and leaf N at Ce was similar for the last fully expanded leaf blade (LFELB) and expanding leaf blade (ELB). Spatial leaf N content in the ELB was highest in the zone of cell division, sharply declined as cell expansion progressed and gradually increased with cell maturation. Maximum reduction in spatial leaf N and Rubisco content was found at Ce only within cell expansion and maturation zones. The spatial leaf N content correlated well with the amount of Rubisco synthesized during leaf expansion, suggesting that N deposition into the expanding leaf blade may be the key for Rubisco synthesis and possibly photosynthetic acclimation to Ce. and S. Seneweera.
Effects of Quercus ilex acorn size on seedling morphological and physiological traits were analysed. The study was carried out with five populations from different geographical areas and covering an aridity gradient. Seedling morphological traits (height and total leaf area) were analyzed during the first growing year. Physiological traits (net photosynthesis, stomatal conductance, leaf transpiration, and intrinsic water-use efficiency) were analysed at different air temperatures during spring, summer, and winter months, and in response to water stress. There were significant correlations among the considered acorn (volume, fresh mass) and seedling traits. Differences in growth and physiological traits among the considered populations were found. The larger differences in the growth parameters were observed during the first growing season, and they could be justified by the significant differences among acorn size. On the contrary, the physiological response to air temperature and aridity was more related to the geographical origin of the considered populations than to acorn size. Q. ilex acorn and seedling traits more tolerant to drought might have a high potential for vegetation recovery in afforestation projects and restoration programmes particularly under water-limited environments or in degraded areas. and A. Bonito ... [et al.].
Two populations, one from lesser saline Derawar Fort (DF) and the other from highly saline Ladam Sir (LS) in the Cholistan desert, for each of the five grass species, Aeluropus lagopoides, Cymbopogon jwarancusa, Lasiurus scindicus, Ochthochloa compressa, and Sporobolus ioclados were examined to investigate the influence of salinity on structural and functional characteristics of stomata. Salinity tolerance in A. lagopoides mainly depended on controlled transpiration rate (E) and high water-use efficiency (WUE), which was found to be regulated by fewer and smaller stomata on both leaf surfaces as well as stomatal encryption by epidermal invaginations. C. jwarancusa had sunken stomata on the abaxial surface only, which largely reflected a reduced E, but less affected stomatal conductance (gs) or WUE. L. scindicus had fewer but larger stomata along with hairs/trichomes which may function to avoid water loss through transpiration, and hence, to attain a high WUE. In O. compressa stomata were found only on the abaxial surface and these were completely encrypted by epidermal invaginations as well as a dense covering of microhairs, which was associated with a low E and high WUE under salinity stress. In S. ioclados, the traits of increased stomatal density and decreased stomatal area may be critical for stomatal regulation under salt-prone environments. High stomatal regulation depended largely on stomatal density, area, and degree of encryption under salinity, which is of great ecophysiological significance for plants growing under osmotic stresses. and N. Naz ... [et al.].
The relationship between the activity of xanthophyll cycle and chlorophyll (Chl) metabolism was investigated using two cultivars, Helan No. 3 (seawater-tolerant cultivar) and Yuanye (seawater-sensitive cultivar), of spinach (Spinacia oleracea L.) plants cultured in Hoagland's nutrient solution, with or without seawater (40%). The results showed that, in plants of two cultivars with seawater, the xanthophyll cycle seems to show a principal protection mechanism against photoinhibition under seawater stress. Furthermore, accumulation of reactive oxygen species (ROS) in chloroplasts of two cultivars was enhanced by seawater to lower the activity of porphobilinogen deaminase. Namely, the conversion of porphobilinogen into uroporphyrinogen III involved in Chl biosynthetic processes was inhibited by seawater. In Helan No. 3 spinach plants with seawater, higher activity of xanthophyll cycle in the leaves dissipated more excess light energy, which appeared to lower the levels of ROS in chloroplasts. As a consequence, the Chl biosynthesis in Helan No. 3 leaves with seawater showed only a weak inhibition and the activity of chlorophyllase (Chlase) was not affected by seawater stress. In contrast, a more pronounced accumulation of ROS in chloroplasts of Yuanye leaves, which possess lower xanthophyll cycle activity, severely inhibited Chl biosynthesis and remarkably enhanced the activity of Chlase, which aggravates the decomposition of Chl. These results suggest that higher activity of xanthophyll cycle in seawater-tolerant spinach plays a role in maintaining Chl metabolic processes, probably by decreasing the levels of ROS, when the plants are cultured in the nutrient solution with seawater (40%). and J. Sun ... [et al.].