1,721,021 research outputs found
Programmed Cell Death And Adaptation: Two Different Types Of Abiotic Stress Response In A Unicellular Chlorophyte
No full textEukaryotic microalgae are highly suitable biological indicators
of environmental changes because they are exposed
to extreme seasonal fl uctuations. The biochemical and
molecular targets and regulators of key proteins involved in
the stress response in microalgae have yet to be elucidated.
This study presents morphological and biochemical evidence
of programmed cell death (PCD) in a low temperature
strain of Chlorella saccharophila induced by exposure to
NaCl stress. Morphological characteristics of PCD, including
cell shrinkage, detachment of the plasma membrane from
the cell wall, nuclear condensation and DNA fragmentation,
were observed. Additionally, a signifi cant production of H 2 O 2
and increase in caspase 3-like activity were detected. We
demonstrated that singly applied environmental stresses
such as warming or salt stress trigger a pathway of PCD.
Intriguingly, the prior application of salt stress seems to
reduce heat shock-induced cell death signifi cantly, suggesting
a combined effect which activates a defense mechanism in
algal cells. These results suggest that C. saccharophila can
undergo PCD under stress conditions, and that this PCD
shares several features with metazoan PCD. Moreover, the
simultaneous exposure of this unicellular chlorophyte to
different abiotic stresses results in a tolerance mechanism
Reproductive Mechanisms in Ginkgo and Cycas: Sisters but not Twins
Full text linkThe study of reproductive mechanisms is of particular interest for a real understanding of seed plant evolution. Spermatophytes comprise angiosperms and four orders of gymnosperms (Cycadales, Ginkgoales, Coniferales, and Gnetales) whose main characteristic is the reproduction via seeds. Ginkgo and cycads form a sister clade to the other gymnosperms and occupy a key phylogenetic position in-between the extinct Paleozoic seed ferns and the other extant gymnosperms. This review focuses on the similarities and differences between the reproductive mechanisms of Ginkgo and Cycas, from the morphogenesis of the male and female organs to the pollination and fertilization events. Together with the morphological and cytological description, the latest available molecular data on the reproductive organ development of the two plant genera are discussed. This will, hopefully, pave the path for new studies aiming at filling the gaps in our understanding of the hormonal and genetic regulation of their reproductive mechanisms. The whole reproductive process is presented in detail, providing a comprehensive and organic picture together with complete illustrations and photographic material. Each phase of the reproductive process is dissected, pointing out the main similarities and differences found among the two genera. The comparison comprises the male and female reproductive organs development, with a focus on pollen ontogeny, shape, ultrastructure, and germination as well as ovule development and patterning, female gametophyte formation, and ovule integument differentiation. Particular attention is given to the pollination and fertilization events focusing on the role of reproductive fluids as well as zoogamy
FePO4 NPs Are an Efficient Nutritional Source for Plants: Combination of Nano-Material Properties and Metabolic Responses to Nutritional Deficiencies
Full text linkPhosphorous and iron are a macro- and micronutrient, respectively, whose low bioavailability can negatively affect crop productivity. There is ample evidence that the use of conventional P and Fe fertilizers has several environmental and economical disadvantages, but even though great expectations surround nanotechnology and its applications in the field of plant nutrition, little is known about the mechanisms underlying the uptake and use of these sub-micron particles (nanoparticles, NPs) by crop species. This work shows that cucumber and maize plants both use the nutrients borne by FePO4 NPs more efficiently than those supplied as bulk. However, morpho-physiological parameters and nutrient content analyses reveal that while cucumber plants (a Strategy I species with regard to Fe acquisition) mainly use these NPs as a source of P, maize (a Strategy II species) uses them preferentially for Fe. TEM analyses of cucumber root specimens revealed no cell internalization of the NPs. On the other hand, electron-dense nanometric structures were evident in proximity of the root epidermal cell walls of the NP-treated plants, which after ESEM/EDAX analyses can be reasonably identified as iron-oxyhydroxide. It appears that the nutritional interaction between roots and NPs is strongly influenced by species-specific metabolic responses
Fleshy Structures Associated with Ovule Protection and Seed Dispersal in Gymnosperms: A Systematic and Evolutionary Overview
Full text linkFleshy structures associated with the ovule/seed arose independently several times during gymnosperm evolution. Fleshy structures are linked to ovule/seed protection and dispersal, and are present in all the four lineages of extant gymnosperms. The ontogenetic origin of the fleshy structures could be different, and spans from the ovule funiculus in the Taxus baccata aril, the ovule integument in Ginkgo biloba, to modified bracts as in case of Ephedra species. This variability in ontogeny is reflected in the morphology and characteristics that these tissues display among the different species. This review aims to provide a complete overview of these ovule/seed-associated fleshy structures in living gymnosperms, reporting detailed descriptions for every genus. The evolution of these independently evolved structures is still unclear, and different hypotheses have been presented—protection for the seeds, protection to desiccation—each plausible but no one able to account for all their independent origins. Our purpose is to offer an extensive discussion on these fleshy structures, under different points of view (morphology, evolution, gene involvement), to stimulate further studies on their origin and evolution on both ecological and molecular levels
Taxonomic re‐examination of nine rosellinia types (Ascomycota, xylariales) stored in the Saccardo mycological collection
Full text linkIn a recent monograph on the genus Rosellinia, type specimens worldwide were revised and re‐classified using a morphological approach. Among them, some came from Pier Andrea Saccardo’s fungarium stored in the Herbarium of the Padova Botanical Garden. In this work, we taxonomically re‐examine via a morphological and molecular approach nine different Rosellinia sensu Saccardo types. ITS1 and/or ITS2 sequences were successfully obtained applying Illumina MiSeq technology and phylogenetic analyses were carried out in order to elucidate their current taxonomic position. Only the ITS1 sequence was recovered for Rosellinia areolata, while for R. geophila, only the ITS2 sequence was recovered. We proposed here new combinations for Rosellinia chordicola, R. geophila and R. horridula, while for R. ambigua, R. areolata, R. australis, R. romana and R. somala, we did not suggest taxonomic changes compared to the current ones. The name Rosellinia subsimilis Sacc. is invalid, as it is a later homonym of R. subsimilis P. Karst. & Starbäck. Therefore, we introduced Coniochaeta dakotensis as a nomen novum for R. subsimilis Sacc. This is the first time that these types have been subjected to a molecular study. Our results demonstrate that old types are an important source of DNA sequence data for taxonomic re‐examinations
Ultrastructural features of the cell wall in the thallus of Scytosiphon lomentaria (Scytosiphonales, Phaeophyta)
No full textFePO(4)NPs Are an Efficient Nutritional Source for Plants: Combination of Nano-Material Properties and Metabolic Responses to Nutritional Deficiencies
Full text linkPhosphorous and iron are a macro- and micronutrient, respectively, whose low bioavailability can negatively affect crop productivity. There is ample evidence that the use of conventional P and Fe fertilizers has several environmental and economical disadvantages, but even though great expectations surround nanotechnology and its applications in the field of plant nutrition, little is known about the mechanisms underlying the uptake and use of these sub-micron particles (nanoparticles, NPs) by crop species. This work shows that cucumber and maize plants both use the nutrients borne by FePO(4)NPs more efficiently than those supplied as bulk. However, morpho-physiological parameters and nutrient content analyses reveal that while cucumber plants (aStrategy Ispecies with regard to Fe acquisition) mainly use these NPs as a source of P, maize (aStrategy IIspecies) uses them preferentially for Fe. TEM analyses of cucumber root specimens revealed no cell internalization of the NPs. On the other hand, electron-dense nanometric structures were evident in proximity of the root epidermal cell walls of the NP-treated plants, which after ESEM/EDAX analyses can be reasonably identified as iron-oxyhydroxide. It appears that the nutritional interaction between roots and NPs is strongly influenced by species-specific metabolic responses
Time course of the response of ascorbate peroxidase and superoxide dismutase activity to ozone exposure in sunflower plants.
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