This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the ge in the genus Oedogonium,from androspore germination to the liberation of mature male gametes.The ultrastructure o...This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the ge in the genus Oedogonium,from androspore germination to the liberation of mature male gametes.The ultrastructure of the process in O.macrandrium Wittrok is similar to that of Bulbochaete hiloensis(Nordstedt)Tiffany,butwith two remarkable differences.In O.macrandrium:(1)instead of a true transverse wall,only condensed mucilage appears between the gametes of each antheridial cell,and (2)the cell wall between the basal cell and the basal most antheridial cell has simple plasmodesmata similar to those present in the transverse walls of vegetative cells,which are absent in B.hiloensis.展开更多
Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,lit...Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,little work has been done on underground responses to those environmental changes.The objective of this work was to determine how Osmorhiza depauperata,Phleum alpinum and Poa pratensis change its root length density and root colonization by mycorrhiza as a function of light availability in a Nothofagus pumilio(i.e.lenga)forest harvested following the variable retention prescription.Methods We selected three microenvironments in an old growth forest harvested by the variable retention prescription:aggregated retention,dispersed retention with influence of aggregated retention and dispersed retention.A non-harvested primary forest(PF),similar to the harvested one,was used as a control.Every 2 months,from October 2008 to April 2009,we took soil cores from randomly selected plants.From these soil cores,root length density and colonization percentage(CP)by arbuscular mycorrhizae were estimated.Important Findings Light availability changed significantly among the microenvironments.In general,root length density was significantly greater in P.pratensis than in P.alpinum and both species greater than in O.depauperata.Light availability increased root length density in all species,although the magnitude of these increases difference among species.Root length density was 187%greater in P.pratensis,101%in P.alpinum and 94%in O.depauperata in the disperse retention system than in the PF.Mycorrhiza CP was higher in O.depauperata than in P.alpinum and P.pratensis.Also,it was lower in the PF than in the harvested microenvironments.CPs were very low.展开更多
基金Funds were provided by the Universidad Nacional del Sur(UNS,SGCyT),Grant PGI 24/B151 to EJC.
文摘This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the ge in the genus Oedogonium,from androspore germination to the liberation of mature male gametes.The ultrastructure of the process in O.macrandrium Wittrok is similar to that of Bulbochaete hiloensis(Nordstedt)Tiffany,butwith two remarkable differences.In O.macrandrium:(1)instead of a true transverse wall,only condensed mucilage appears between the gametes of each antheridial cell,and (2)the cell wall between the basal cell and the basal most antheridial cell has simple plasmodesmata similar to those present in the transverse walls of vegetative cells,which are absent in B.hiloensis.
基金Agencia Nacional de Promoción Científica y Tecnológica(PAV2004-22428).L.J.Selzer was recipient of a doctoral scholarship by CONICET.
文摘Aims Forest canopy openings modify the natural environment,producing changes in light quality and intensity,precipitation and temperature.In turn,these changes promote the acclimation of understory species.However,little work has been done on underground responses to those environmental changes.The objective of this work was to determine how Osmorhiza depauperata,Phleum alpinum and Poa pratensis change its root length density and root colonization by mycorrhiza as a function of light availability in a Nothofagus pumilio(i.e.lenga)forest harvested following the variable retention prescription.Methods We selected three microenvironments in an old growth forest harvested by the variable retention prescription:aggregated retention,dispersed retention with influence of aggregated retention and dispersed retention.A non-harvested primary forest(PF),similar to the harvested one,was used as a control.Every 2 months,from October 2008 to April 2009,we took soil cores from randomly selected plants.From these soil cores,root length density and colonization percentage(CP)by arbuscular mycorrhizae were estimated.Important Findings Light availability changed significantly among the microenvironments.In general,root length density was significantly greater in P.pratensis than in P.alpinum and both species greater than in O.depauperata.Light availability increased root length density in all species,although the magnitude of these increases difference among species.Root length density was 187%greater in P.pratensis,101%in P.alpinum and 94%in O.depauperata in the disperse retention system than in the PF.Mycorrhiza CP was higher in O.depauperata than in P.alpinum and P.pratensis.Also,it was lower in the PF than in the harvested microenvironments.CPs were very low.
