<p>Denna undersökning handlar om elevers kunskaper och uppfattningar angående höstlöven och nedbrytning i naturen. Studien har gjorts på två skolor i årskurs 3. Skola A har profilen ”Natur och Miljö” och skola B är en större skola utan profil. Syftet med arbetet är dels att kartlägga elevers föreställningar om nedbrytning i naturen och dels att undersöka hur man kan arbeta med ämnet i skolan för att få en god lärandemiljö. Elever i årskurs 3 intervjuades och resultatet berättar att alla elever är medvetna om lövfällningen. Sedan skiljer sig kunskaperna åt. Hälften av eleverna på skola A förklarar att löven blir till jord. På skola B nämner ingen elev det. Mer än hälften av eleverna på skola A och två på skola B berättar att jord bildas av ätande maskar och småkryp. Skillnaden tror jag beror på att skola A komposterar. De flesta elever anger skolan som kunskapskälla. Genom att tidigare börja arbeta med kretsloppstänkande i skolan så skulle barnens förståelse utvecklas.</p> / <p>This study examines pupils’ knowledge and conceptions concerning the autumn leaves and decomposition in nature. The investigation took place at two schools. School A has the profile ”Nature and Environment” and school B is a larger school without a profile. The purpose of this work is partly to map pupils’ ideas about decomposition in nature and partly to investigate how to work with the subject in school to get a good learning environment. Pupils in third grade were interviewed and the results show that all pupils are conscious of the leaves falling. Half the pupils at school A explain that the leaves become only soil but no one mentioned that at school B. More than half the pupils at school A and two at school B told that soil comes from worms and small animals feeding. I think the difference between the schools depends on the composting at school A. Most pupils state school as a source of knowledge. Talking about the cycle of matter at an earlier stage could develop children’s understanding.</p>

Denna undersökning handlar om elevers kunskaper och uppfattningar angående höstlöven och nedbrytning i naturen. Studien har gjorts på två skolor i årskurs 3. Skola A har profilen ”Natur och Miljö” och skola B är en större skola utan profil. Syftet med arbetet är dels att kartlägga elevers föreställningar om nedbrytning i naturen och dels att undersöka hur man kan arbeta med ämnet i skolan för att få en god lärandemiljö. Elever i årskurs 3 intervjuades och resultatet berättar att alla elever är medvetna om lövfällningen. Sedan skiljer sig kunskaperna åt. Hälften av eleverna på skola A förklarar att löven blir till jord. På skola B nämner ingen elev det. Mer än hälften av eleverna på skola A och två på skola B berättar att jord bildas av ätande maskar och småkryp. Skillnaden tror jag beror på att skola A komposterar. De flesta elever anger skolan som kunskapskälla. Genom att tidigare börja arbeta med kretsloppstänkande i skolan så skulle barnens förståelse utvecklas. / This study examines pupils’ knowledge and conceptions concerning the autumn leaves and decomposition in nature. The investigation took place at two schools. School A has the profile ”Nature and Environment” and school B is a larger school without a profile. The purpose of this work is partly to map pupils’ ideas about decomposition in nature and partly to investigate how to work with the subject in school to get a good learning environment. Pupils in third grade were interviewed and the results show that all pupils are conscious of the leaves falling. Half the pupils at school A explain that the leaves become only soil but no one mentioned that at school B. More than half the pupils at school A and two at school B told that soil comes from worms and small animals feeding. I think the difference between the schools depends on the composting at school A. Most pupils state school as a source of knowledge. Talking about the cycle of matter at an earlier stage could develop children’s understanding.

Autumn senescence is a visually spectacular phenomenon in which trees prepare for the oncoming winter. The mechanism for regulation of autumn senescence in trees has been very hard to pinpoint. In this thesis the main focus is to investigate how autumn senescence is regulated in aspens (Populus tremula). Previous work has established that autumn senescence in aspens is under daylight control, in this thesis the metabolic status and the effect on autumn senescence was investigated. The metabolic status was altered by girdling which leads to accumulation of photosynthates in the canopy. This resulted in an earlier onset of senescence but also the speed of senescence was changed. At the onset of senescence the girdled trees also accumulated or retained anthocyanins. The nitrogen status of aspens during autumn senescence was also investigated, we found that high doses of fertilization could significantly delay the onset of senescence. The effects of various nitrogen forms was investigated by delivering organic and inorganic nitrogen through a precision fertilization delivery system that could inject solutes directly into the xylem of the mature aspens. The study showed that addition of nitrate delayed senescence, addition of arginine did not have any effect on the autumn senescence in aspens, and furthermore the nitrate altered the trees leaf metabolism that was more profound in high dosages of supplied nitrate.  Cytokinins are plant hormones believed to delay or block senescence, studies have suggested that the decrease of cytokinins and/or cytokinin signalling may precede senescence in some plants. To investigate how cytokinin regulates autumn senescence in aspens we profiled 34 cytokinin types in a free growing mature aspen. The study begun before autumn senescence was initiated and ended with the shedding of the leaves, and spanned three consecutive years. The study showed that the individual cytokinin profiles varied significantly between the years, this despite that senescence was initiated at the same time each year. Senescence was furthermore not connected to the depletion of either active or total cytokinins levels. The gene pattern of genes known to be associated with cytokinin was also studied, but no gene expression pattern that the profile generated could explain the onset of senescence. These results suggest that the depletion of cytokinins is unlikely to explain the tightly regulated onset of autumn leaf senescence in aspen.