Search results for "botany"
showing 10 items of 4586 documents
Formation of spicules by sclerocytes from the freshwater spongeEphydatia muelleri in short-term cultures in vitro
1995
Cells from the freshwater sponge Ephydatia muelleri were isolated by dissociating hatching gemmules. During the first 24 h the cells reaggregated, but the aggregates progressively disintegrated again to single cells, among which the spicule-forming sclerocytes were recognized. Such cultures were used to study spicule (megascleres) formation in vitro. The isolated sclerocytes formed the organic central axial filament onto which they deposited inorganic silicon. The size of the spicules (200 to 350 microns in length) as well as the rate of spicule formation (1 to 10 microns/h) under in vitro conditions were similar to the values measured in vivo. Immediately after completion of spicule format…
Effects of 2-month ozone exposure in spinach leaves on photosynthesis, antioxidant systems and lipid peroxidation
2003
The photosynthesis response, antioxidant systems and lipid peroxidation were studied in leaves from spinach plants (Spinacia oleracea L.) in response to ozone fumigation, ambient air and charcoal filtered air treatments. The photosynthetic activity was tested through gas exchange and chlorophyll a fluorescence measurements. Ambient air and ozone fumigation caused a decrease in the photosynthetic rate (25% and 63%, respectively) mainly due to a reduced mesophyll activity, as evidenced by the increased intercellular CO, concentration. These data agree with a large reduction in the non-cyclic electron flow (7% and 16%), a lower capacity to reduce the quinone pool and a higher development of no…
Sorbus busambarensis (Rosaceae), a new endemic species of Sicily
2012
Abstract In this study, Sorbus busambarensis, a new species from Rocca Busambra (Palermo, NW Sicily) has been described and named. On the basis of the critical features of its flowers, fruits and leaves, it is noted to be a member of S. sect. Aria and is related to the other taxa that form the polymorphic group of S. aria, which in Sicily is represented by S. aria s. str., S. graeca and S. umbellata.
Effects of temperature and desiccation on ex situ conservation of nongreen fern spores
2012
Premise of the study Fern spores are unicellular and haploid, making them a potential model system to study factors that regulate lifespan and mechanisms of aging. Aging rates of nongreen spores were measured to compare longevity characteristics among diverse fern species and test for orthodox response to storage temperature and moisture. Methods Aging of spores from 10 fern species was quantified by changes in germination and growth parameters. Storage temperature ranged from ambient room to -196°C (liquid nitrogen); spores were dried to ambient relative humidity (RH) or using silica gel. Key results Survival of spores varied under ambient storage conditions, with one species dying within …
Pythium regulare sp. nov., Isolated from the Canary Islands, Its Taxonomy, Its Region of rDNA, and Comparison with Related Species
2003
Pythium regulare (CI-34) was isolated from some soil samples taken in the Canary Islands (Spain). This new species is very closely related to P. irregulare isolated from pea roots in The Netherlands by Buisman in 1927. The species of Pythium are members of the kingdom Chromista. Pythium regulare is characterized by its ornamented oogonia bearing blunt or digitate spines, and its non-sporulating type of sporangia or hyphal bodies, its aplerotic oospores, its monoclinous and diclinous antheridia that at times crowd around the oogonia. The taxonomic description of this oomycete, the PCR of the internal transcribed region (spacers ITS1, ITS2, and the gene 5.8 S) of its ribosomal nuclear DNA as …
Pythium carbonicum, a new species isolated from a spoil heap in northern France, the ITS region, taxonomy and comparison with related species.
2003
Pythium carbonicum (F-72) sp. nov. was found in soil samples taken on the top of a spoil heap in northern France. The morphology of this new species resembles that of a recently described species: Pythium megacarpum. However, the antheridial and oogonial characteristics of this new species are unique, and the comparison of its ITS region of the nuclear ribosomal DNA indicates that this species is also related to the genus Phytophthora. The fungus does not sporulate, the sporangia germinate directly into mycelium through germ tubes. The oogonia of P. carbonicum are smooth-walled and also papillated, and are provided with monoclinous and diclinous antheridia that wrap around, forming a compli…
Water properties in fern spores: sorption characteristics relating to water affinity, glassy states, and storage stability.
2007
Ex situ conservation of ferns may be accomplished by maintaining the viability of stored spores for many years. Storage conditions that maximize spore longevity can be inferred from an understanding of the behaviour of water within fern spores. Water sorption properties were measured in spores of five homosporeous species of ferns and compared with properties of pollen, seeds, and fern leaf tissue. Isotherms were constructed at 5, 25, and 45 degrees C and analysed using different physicochemical models in order to quantify chemical affinity and heat (enthalpy) of sorption of water in fern spores. Fern spores hydrate slowly but dry rapidly at ambient relative humidity. Low Brunauer-Emmet-Tel…
Calorimetric properties of water and triacylglycerols in fern spores relating to storage at cryogenic temperatures.
2007
Abstract Storing spores is a promising method to conserve genetic diversity of ferns ex situ . Inappropriate water contents or damaging effects of triacylglycerol (TAG) crystallization may cause initial damage and deterioration with time in spores placed at −15 °C or liquid nitrogen temperatures. We used differential scanning calorimetry (DSC) to monitor enthalpy and temperature of water and TAG phase transitions within spores of five fern species: Pteris vittata , Thelypteris palustris , Dryopteris filix-mas , Polystichum aculeatum , Polystichum setiferum . The analyses suggested that these fern spores contained between 26% and 39% TAG, and were comprised of mostly oleic ( P. vittata ) or …
Occurrence of non-basic metabolites in Amaryllidaceae
1969
Abstract Narciclasine and margetine, previously extracted from many species of the genus Narcissus , are also present in the genera Galanthus , Haemanthus , Leucojum , Pancratium , Sprekelia , Sternbergia and Vallota . In the genus Hymenocallis only margetine was detected, but not narciclasine. Both products are absent in the genera Amaryllis , Clivia , Crinum and Nerine .
Consistent isotopic differences between Schistocephalus spp. parasites and their stickleback hosts
2015
Published version available at http://dx.doi.org/10.3354/dao02893 Parasite−host systems show markedly variable patterns in isotopic fractionation: parasites can be either depleted or enriched in 15N and 13C as compared to their hosts. However, it remains unknown whether isotopic fractionation patterns are similar in comparable parasite−host systems from markedly different ecosystems. Results of this study show that large-sized Schistocephalus spp. endoparasites are consistently depleted in 15N (by on average −2.13 to −2.20‰) as compared to their nine-spined stickleback Pungitius pungitius and three-spined stickleback Gasterosteus aculeatus hosts. The differences between parasites and host f…