866 research outputs found
Do plants require nutrients in similar proportions?
Within the field of plant nutrition, specific nutritional requirements in plants are under constant scrutiny. In the predominant paradigm, it is held as a commonly accepted fact that different plant species have considerably different nutrient requirements, concerning the mutual proportions between the nutrients. However, the ruling paradigm shows signs of incoherence and give several
examples of inconsistencies, sometimes even outright contradictions. As a result of profound research over the last four decades an elaborate contending theory have emerged. Its central hypothesis states that all terrestrial plants have the same basic nutritional requirements, concerning the mutual proportions between the nutrients, due to the same basic physiology. Foundational
literature representing the predominant paradigm were surveyed. Likewise was the published materials from the research leading up to the challenging hypothesis. The issue were primarily compared through the medium of hydroponic production of soilless culture, due to the systems quantifiable properties. The results indicates that the validity of the predominant paradigm is questionable. Particularly in the light of the contending hypothesis, which stands strong under the lens of scrutiny. It were concluded that it is valid to question the legitimacy of the predominant paradigm, and that it is sensible to further investigate the challenging hypothesis
Minimized nutrient leaching through fertilizer management
Nutrient leaching causing surface- and groundwater pollution and eutrophication is one of the main environmental problems of modern society. Plant production is among the quantitatively most important sources of nutrient leaching, particularly of nitrogen and phosphorus, which stands in focus in remediating these problems. One of the most important measures to be taken is to apply fertilizers in a correct way to meet the needs of the plants while preventing any nutrients to leach. The rather unnoticed theory and method of the demand-driven fertilization strategy, which means to supply the plant with nutrients according to its momentary demand, was compared with representative fertilization strategies commonly used in current commercial plant production. Then the demand-driven driven strategy was compared with three other strategies in a pot experiment: (1) a linear nutrient supply on a daily basis, (2) an approximately linear nutrient supply added twice a week, and (3) a onetime application with all the fertilizers added in the beginning. Uptake and leaching of N and P was measured for all treatments. The results clearly showed that the demand-driven strategy leached the least and had the highest uptake in relation to the added amount of N and P, and that the onetime application leached the most. It was concluded that the demand-driven strategy had highest potential in amending nutrient leaching, and that further studies most likely would be fruitful.Behovsanpassad gödsling som ger höga skördar utan att belasta miljön
Behovsanpassad gödsling
I ett kÀrlförsök jÀmförde jag en unik och förvÄnansvÀrt ouppmÀrksammad gödslingsmetod kallad behovsanpassad gödsling, som utvecklades vid SLU för ett antal decennier sedan, med traditionell gödsling.
Hur olika gödslingsmetoder inverkar pÄ miljön
Jag jÀmförde fyra olika metoder att förse vÀxter med vÀxtnÀring och mÀtte bÄde vÀxternas nÀringsupptag och nÀringslÀckage vid flera tillfÀllen under tillvÀxtperioden. De fyra metoderna var: (1) all vÀxtnÀring tillsattes i en giva handelsgödsel nÀr odlingen pÄbörjades, (2) vÀxtnÀring tillsattes med bevattningsvattnet i lika stora smÄportioner 2 gÄnger per vecka igenom hela försöket, (3) vÀxtnÀring tillsattes med bevattningsvattnet i lika stora smÄportioner dagligen igenom hela försöket, och (4) vÀxtnÀring tillsattes pÄ samma sÀtt som i (3) med skillnaden att mÀngden vÀxtnÀring varierade med vÀxtens behov, s.k. behovsanpassad gödsling. Solrosplantor i krukor odlades och mÀngden vÀxtnÀring i vÀxterna och i lakvattnet som samlades upp under krukorna analyserades kontinuerligt.
Resultaten var entydiga; behovsanpassad gödsling ledde till högst upptag av tillsatt vÀxtnÀring och minimerade nÀringslÀckage. Alla former av nÀringstillförsel via bevattning kan förebygga nÀringslÀckage jÀmfört med gödsling i fast form. Det som visade sig vara mest optimalt var att fördela gödselgivan under hela vÀxtsÀsongen efter vÀxtens behov tillsammans med bevattningen, och minst optimalt var att ge en stor giva handelsgödsel vid ett enda tillfÀlle vid pÄbörjat odlingstillfÀlle.
En mycket positiv aspekt Àr att behovsanpassad gödsling med bevattning dessutom ger lika höga, eller högre skördar, Àn de andra metoderna. För en professionell odlare mÄste det finnas en möjlighet att installera en bevattningsanlÀggning och att det Àr lönsamt för odlaren att investera i ett sÄdant system. För hobbyodlaren Àr det enklare. Han kan tillföra vÀxtnÀringen efter behov nÀr han vattnar.
Olika miljöproblem till följd av att gödsling inte Àr optimal
Ăvergödning av vĂ„ra vatten, sĂ„vĂ€l sjöar som hav, Ă€r ett stort problem pĂ„ mĂ„nga platser. Detta pĂ„verkar frĂ€mst floran och faunan i vĂ„ra vatten pĂ„ ett negativt sĂ€tt, men Ă€ven samhĂ€llets dricksvattenkvalitet, giftiga algblomningar pĂ„ badplatser och kan Ă€ven utgöra en en större belastning av bĂ„de reningsverk och vattenverk.
Ăvergödning och försĂ€mrad vattenkvalitet beror till stor del pĂ„ nĂ€ringslĂ€ckage, dvs vĂ€xtnĂ€ring som inte kommer vĂ€xterna till godo, utan som istĂ€llet via grundvattnet hamnar i vattendrag och slutligen i sjöar och hav. För att förhindra dessa problem Ă€r det viktigt att pĂ„ alla sĂ€tt optimera vĂ€xttnĂ€ringstillförseln och pĂ„ sĂ„ sĂ€tt minimera nĂ€ringslĂ€ckaget. Det innebĂ€r att anvĂ€nda den gödslingsmetod som möjliggör att vĂ€xterna tillgodogör sig den tillförda nĂ€ringen i sĂ„ hög grad som möjligt Ă€r en mycket anglĂ€gen uppgift.
Behovsanpassad gödsling har stora förutsÀttningar att bidra med just detta. Om man i ett odlingssammanhang anvÀnder bevattning, kan behovsanpassad gödsling minska nÀringslÀckaget pÄtagligt. Eftersom metoden dessutom pÄvisat goda skörderesultat finns det ett ekonomiskt motiv för producenter att tillÀmpa den. En ytterligare positiv effekt med metoden Àr att den krÀver mindre mÀngd gödsel per producerad mÀngd skörd, vilket Àr en ekonomisk fördel för odlare och för hushÄllningen med Àndliga resurser.
Slutligen, nÀr metoden togs fram, upptÀcktes det att landlevande vÀxter har ganska likartat behov vad gÀller sammansÀttningen av gödselmedel. Detta gör att metoden Àr relevant för de flesta odlare, och kan tillÀmpas pÄ olika befintliga gödslingsmetoder
Regional distribution of some enzymes involved with putative neurotransmitters in the human visual system
Levels of protein and activity of several enzymes were determined in different portions of the visual system of the human brain. The enzymes studied were total cholinesterase (TChE), acetylcholinesterase (AChE), pseudocholinesterase (ChE), choline acetyltransferase (ChAc), monoamine oxidase (MAO), and N-methyltransferase (NMT). Brains of 17 patients were obtained at autopsy. The specimens were divided into 3 groups. One group consisted of the brains of subjects who were mentally normal prior to death. The second group of subjects had been diagnosed as chronic schizophrenics and the third had an organic brain syndrome. Each group included males and females. Subjects with an organic brain syndrome were significantly older than subjects in either of the other two groups. There were no significant differences in protein among the 3 groups for most of the visual areas. All enzyme activity was expressed per g of protein. TChE, AChE, and ChE activity varied markedly within the visual system, being usually lowest in the optic nerve and highest in the superior colliculus. There were no significant differences in TChE or AChE among the diagnostic groups. Unexpectedly, ChE was elevated in some brain areas in the chronic schizophrenic group. This finding needs further confirmation in a drug free group. ChAc did not differ significantly among the 3 diagnostic groups and, in general, was low throughout the visual system but highest in the superior colliculus and lateral geniculate. MAO activity was not significantly different among the 3 patient groups. Its activity in the gray matter was only slightly higher than in the white matter of the visual system. NMT activity was extremely low (about 0.1% the activity of the other enzymes) throughout all areas studied and did not differ significantly between areas or diagnostic groups.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33831/1/0000088.pd
Choline acetyltransferase detection in normal and denervated electrocyte from Electrophorus electricus (L.) using a Confocal Scanning Optical Microscopy Analysis
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