The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
U K Vogt - One of the best experts on this subject based on the ideXlab platform.
-
hydraulic vulnerability vessel refilling and seasonal courses of stem water potential of sorbus aucuparia l and sambucus nigra l
Journal of Experimental Botany, 2001Co-Authors: U K VogtAbstract:Differences in the seasonal variation in stem water potential between the two shrub species Sorbus aucuparia and Sambucus nigra were related with their vulnerability to xylem cavitation. It was also demonstrated indirectly that the two species differ in the extent to which they reverse cavitation. Seasonal variation in stem water potential was investigated during three growing seasons with in situ stem psychrometers. Sorbus experienced wide water potential variations and reached a minimum of -4.2 MPa during drought. Under the same microclimatic conditions, Sambucus experienced consistent stem water potentials with a minimum of -1.7 MPa. The relationship between percentage loss in hydraulic conductivity (PLC) and water potential (hydraulic vulnerability curve) of the two species differed in shape: a flat curve with nearly total loss of conductivity at -6 MPa was found for SORBUS: Sambucus showed a steep vulnerability curve with 90% loss conductivity at -2.2 MPa. Thus, Sambucus is extremely vulnerable to cavitation, but Sorbus is an almost invulnerable species. This different cavitation resistance adjusted the ranges of field stem water potential that the species experienced. Finally, seasonal courses of naturally occurring (native) embolism were compared with calculated PLC courses. This comparison indicates that Sorbus did not refill embolized xylem vessels whereas Sambucus reversed embolism. It was concluded that species which are highly vulnerable to cavitation and drought-induced embolism need refilling of embolized vessels as well as isohydric water potential patterns as two strategies of survival.
-
stem water potential and leaf conductance a comparison of sorbus aucuparia and sambucus nigra
Physics and Chemistry of The Earth Part B-hydrology Oceans and Atmosphere, 1999Co-Authors: U K Vogt, Robert LoschAbstract:Abstract Sorbus aucuparia is a pioneer wood which can naturally be found on extreme habitats, e.g. rocky slopes and mountain forests. Sambucus nigra is a species of flood-plain forests. The different strategies of survival of these two species were studied on planted shrubs which were exposed to the same microclimatic conditions in the outdoors of the Botanical Garden of Diisseldorf University. This situation - both species in direct neighbourhood - also exists where Sorbus aucuparia and Sambucus nigra are brought together by man in common habitats like hegerows. Measurements of stem water potential and leaf conductance were carried out on these planted shrubs during the growing season of 1995 under natural conditions. A hot dry period caused a decrease of stem water potential of Sorbus aucuparia below −4 MPa, while Sambucus nigra merely reached a minimum of −1.64 MPa. Sambucus had a lower maximum of leaf conductance than Sorbus and avoided a decrease of stem water potential by reducing leaf conductances early after the beginning of drought. By contrast Sorbus aucuparia showed high leaf conductance,; during one month of drought until water potentials of the shrub had been fallen below −4 MPa. These contrasting patterns of seasonal variations of water potential and stomatal control of transpiration confirm the classification of Sorbus aucuparia as a hydrolabile and Sambucus nigra as a hydrostabile species.
Hiroyuki Mizuta - One of the best experts on this subject based on the ideXlab platform.
-
Regulation of Sorus Formation by Auxin in Laminariales Sporophyte
Journal of Applied Phycology, 2006Co-Authors: Tomoki Kai, Hajime Yasui, Kazumi Nimura, Hiroyuki MizutaAbstract:Young sporophytes of Laminaria japonica Areshoug were cultured in six indole-acetic acid (IAA) concentrations (0, 10−8, 10−7, 10−6, 10−5, 10−4 M) to examine the effect of auxin on growth. The effects of auxin on Sorus formation were also examined by using discs taken from the adult sporophyte. The auxin contents and IAA oxidase activities in the thallus and Sorus parts of the sporophyte were determined with the blade and sporophyll of other Laminariales plants, Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman. The young sporophytes of L. japonica showed highest elongation rate in 10−5 M IAA. In contrast, the Sorus formation on the discs cultured in 10−5 M IAA was markedly delayed in comparison with other concentrations, indicating that Sorus formation was suppressed by IAA. Free and conjugated auxin contents were lower in the reproductive parts than in the vegetative parts. In three Laminariales sporophytes, IAA oxidase activity was about 3–9 times higher in the reproductive parts than in the vegetative parts. Taken together these results suggest that the growth and reproduction of Laminariales sporophytes are regulated by internal auxin levels. Elucidating the regulation mechanism is likely to provide information that is important for the management of plant production and the assessment of the physiological status of plants in the field.
-
Sorus development on median and marginal parts of the sporophyte of laminaria japonica areschoug phaeophyceae
Journal of Applied Phycology, 1999Co-Authors: Hiroyuki Mizuta, Kazumi Nimura, Hirotoshi YamamotoAbstract:Sorus formation on median and marginal parts of Laminaria japoncia Areschoug was investigated by cultivating sporophytes from December 1996 to September 1997 in Southern Hokkaido, Japan. Simultaneously, discs (ca. 3 cm in diameter) that were cut off monthly from median and marginal parts of the cultivated sporophytes were incubated in our laboratory. All the cultivated sporophytes formed sori on the median parts from January to August, while all the median and marginal discs formed sori at 10 under 46 μmol photon m-2s-1 (12L:12D) in enriched medium. There was no difference in Sorus area between median and marginal discs. These results indicated that the marginal parts are able to produce sori, although the greater part of them are actually washed away before forming sori in the sea. The marginal part is probably in a state of `resource limitation' on the reproduction because the resource outflowed from this part to the basal part for the growth of sporophytes.
Klaus Luning - One of the best experts on this subject based on the ideXlab platform.
-
development of saccharina latissima phaeophyceae kelp hatcheries with year round production of zoospores and juvenile sporophytes on culture ropes for kelp aquaculture
Journal of Applied Phycology, 2012Co-Authors: Silje Forbord, Johanne Arff, Aleksander Handa, Kjell Inge Reitan, Rasmus Bjerregaard, Jorunn Skjermo, Klaus LuningAbstract:Saccharina latissima is attractive for industrial cultivation for different usages, such as biofuels, feed supplements, and derivation of chemicals. A continuous supply of kelp sporelings throughout the year may ensure a year-round production of kelp juveniles on ropes. In this study, induction of sporangial areas (Sorus portions) on the blade of S. latissima was performed throughout the year at three locations: Trondheim (Norway), Grenaa (Denmark), and Sylt island (Germany). The results indicate that a year-round Sorus induction in S. latissima is possible and that this induction is controlled by applying short-day treatment of adult sporophytes throughout the year and by the removal of the basal blade meristem. The artificially induced and released zoospores formed viable sporelings at all seasons, but cultivation in the sea in Norway was successful only during autumn, winter, and spring, while the growth conditions were poor during the summer. The results are important for industrial scale-up and continuous production of kelp biomass.
-
isolated distal blade discs of the brown alga laminaria digitata form Sorus but not discs near to the meristematic transition zone
Journal of Applied Phycology, 1999Co-Authors: Cornelia Buchholz, Klaus LuningAbstract:Blade discs of vegetative thalli of Laminaria digitata (Huds.) Lamour. from Helgoland (North Sea) cut at 5–15 cm distance from the blade/stipe transition, formed Sorus in the laboratory after 7–12weeks, 5 months earlier than whole fronds in the field. Sorus formation occurred in a broad range of daylength regimes or temperatures, at 8–16 h light pe rday and 6–12 °C. No Sorus was developed during three months by meristematic blade discs cut from the lowermost 3 cm portion of the blade, nor from whole thalli cultured in parallel to isolated blade discs. These findings point to the possible existence of sporulation inhibitors produced by the laminarian meristem.
B C Choudhury - One of the best experts on this subject based on the ideXlab platform.
-
mortality of sarus cranes grus antigone due to electricity wires in uttar pradesh india
Environmental Conservation, 2005Co-Authors: K S G Sundar, B C ChoudhuryAbstract:Although overhead electrical wires are known to have caused severe declines of bird populations, there are no studies in India that address this danger, even for endangered species. Rates of mortality, factors affecting mortality and population effects of electrical wires on the globally endangered sarus crane ( Grus antigone ) were assessed for breeding and non-breeding cranes in Etawah and Mainpuri districts, Uttar Pradesh, India. Non-breeding cranes were most susceptible to wires and, within territories, mortalities were higher for pre-dispersed young. Similar proportions of non-breeding and breeding cranes were killed, together accounting for nearly 1% of the total sarus crane population annually. Supply wires accounted for the majority of sarus crane deaths, and only non-breeding cranes were killed by both supply and high-tension power lines. Non-breeding crane deaths at roost sites were correlated with numbers of roosting birds and numbers of wires at each site. Over 40% of 251 known sarus crane territories had at least one overhead wire posing a risk to breeding adults and pre-dispersed young. A risk index for wires over territories of cranes was computed; mortality was not affected by increasing the number and therefore risk posed by wires. Most crane deaths in territories occurred as a result of wires at edges of territories. Wires around roosting sites, territoriality and age of sarus cranes appear to be the most important factors affecting their mortality due to wires. Mitigation measures will be most effective around roost sites and for wires that border territories of breeding pairs.
Michael J Lydeamore - One of the best experts on this subject based on the ideXlab platform.
-
calculation of the age of the first infection for skin sores and scabies in five remote communities in northern australia
Epidemiology and Infection, 2018Co-Authors: Michael J Lydeamore, Patricia T Campbell, Will Cuningham, Ross M Andrews, Therese Kearns, D Clucas, Gundjirryirr R Dhurrkay, Jonathan R CarapetisAbstract:Prevalence of skin sores and scabies in remote Australian Aboriginal communities remains unacceptably high, with Group A Streptococcus (GAS) the dominant pathogen. We aim to better understand the drivers of GAS transmission using mathematical models. To estimate the force of infection, we quantified the age of first skin sores and scabies infection by pooling historical data from three studies conducted across five remote Aboriginal communities for children born between 2001 and 2005. We estimated the age of the first infection using the Kaplan-Meier estimator; parametric exponential mixture model; and Cox proportional hazards. For skin sores, the mean age of the first infection was approximately 10 months and the median was 7 months, with some heterogeneity in median observed by the community. For scabies, the mean age of the first infection was approximately 9 months and the median was 8 months, with significant heterogeneity by the community and an enhanced risk for children born between October and December. The young age of the first infection with skin sores and scabies reflects the high disease burden in these communities.
