Rotexudat - inverkan på mineralisering och naturlig kelatering

http://jeq.scijournals.org/cgi/content/full/30/6/1911
Kortfattat: Jord+Rotexkret = bättre biodegradering av godis.

http://www.vaxteko.nu/html/sll/sjv/utan_serietitel_sjv/UST92-3/UST92-3I.BAK
"Rotspetsen växer genom jorden och utsöndrar kol i form av socker, organiska syror, gelatinösa substanser, s k mucigel och avstötta rotceller. Kolet aktiverar energibegränsade bakterier i vilstadium. Bakterierna börjar bearbeta det organiska materialet och frigör därvid så mycket kväve som krävs för nya bakteriers tillväxt. I varje enskild nisch i jorden tillväxer bakterierna tills rotkolspulsen tar slut. Från att ha varit mycket otillgängligt bundet i dött organiskt material har kvävet nu överförts till ett litet proteinpaket och till attraktiv föda för bl a protozoer...... När protozoer konsumerar bakterier mineraliseras kväve och frigörs som NH4+ till markvattnet nära roten..."

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=106249
"On the other hand, leaf exudates, such as carbohydrates, amino acids, and organic acids (37) may support bacterial densities of up to 5 × 107 CFU/g (fresh weight) under humid conditions (23). In addition, the structurally complex leaf surface, consisting of epidermal cells, interstitial spaces, trichomes, and stomata (7, 22), may provide bacteria with survival habitats. Both availability of growth substrates, a high bacterial density, and the presence of solid surfaces are believed to stimulate conjugal transfer ("

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-8137.2004.01256.x?journalCode=nph
"Acetic, malic and citric acids increased the uptake of lanthanum (La) by barley (Hordeum vulgare) roots and enhanced La content in shoots under hydroponic conditions."

http://webspace.pss.okstate.edu/olga.walsh/Research%20Papers/Phytoremediation.htm
"Enhanced Rhizosphere Biodegradation utilizes plant natural ability to produce and release of root exudates (organic acids, enzymes, sugars) in order to attract beneficial microorganisms like Bacillus and Pseudomonas species, which are biologically degrading the organic contaminants ( )such as and using them as an energy source.
Phytodegradation is also driven by the production of root exudates; the difference, however, is that the exudates themselves act as the degrading agents in decontamination of organic pollutants."

http://209.85.135.104/search?q=cache:_TsHIfefjqAJ:www.epa.gov/ada/download/issue/epa_540_s01_500.pdf+%22root+exudates%22+%22water+hyacinth%22+chelating&hl=sv&ct=clnk&cd=1&gl=se
"Exudates such as simple phenolics and other organic acids can
be released from living cells or from the entire cell contents
during root decay. These exudates can change metals speciation
(i.e., form of the metal), and the uptake of metal ions and
simultaneous release of protons, which acidifies the soil and
promotes metal transport and bioavailability (Ernst, 1996). In
some cases, the changed metals speciation can lead to increased
precipitation of the metals. The organic compounds in the root
exudates can stimulate microbial growth in the rhizosphere (the
region immediately surrounding plant roots)."

"Significantly higher
populations of total heterotrophs, denitrifiers, pseudomonads,
BTX (benzene, toluene, xylenes) degraders, and atrazine
degraders were found in rhizosphere soil around hybrid poplar
trees in a field plot (Populus deltoides × nigra DN-34, Imperial
Carolina) than in non-rhizosphere soil (Jordahl et al., 1997). The
increased microbial populations are due to stimulation by plant
exudates, compounds produced by plants and released from
plant roots. Plant exudates include sugars, amino acids, organic
acids, fatty acids, sterols, growth factors, nucleotides, flavanones,
enzymes, and other compounds (Shimp et al., 1993). "

http://fwrc.msstate.edu/pubs/keith.pdf
"Root exudates from
the water hyacinth could have kept copper soluble or suspended
in water, thus showing higher amount of copper in the samples with
plants"

http://www.gsd.harvard.edu/users/yavanian/phyto_processes_main.html
"Root exudates are compounds produced by plants and released from plant roots. They include sugars, amino acids, organic acids, fatty acids, sterols, growth factors, nucleotides, flavanones, enzymes, and other compounds. The microbial populations and activity in the rhizosphere can be increased due to the presence of these exudates,"


EDIT: En slutsats jag drar av det här är att växterna är bra på att skapa den miljö dom vill ha och att fixa så att vissa ämnen bibehålls i lösning med hjälp av olika typer av syror. Att göra 100% vattenbyten är därför (väldigt) korkat.

Det är även bra att ha organiskt nedbrytbart material (DOC) i bottnen som tillsammans med rotexudaten ger en markant bättre tillgång till näring för växterna.

Att producera dessa exudat är energikrävande, dvs kräver en hel del ljus.