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MINERALNA PREHRANA RASTLIN
Agronomija - UNI
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DUŠIK
PRIVZEM: NH4+ (pasiven)
NO3- (aktiven, H-kotransport)
fiksacija N2
TRANSPORT:- dobro mobilen v rastlini- transportne oblike amida glutamin (2N/5C)in asparagin (2N/4C), aminokislina arginin (4N/6C), ureida alantoin in alantoinska kislina (4N/4C)
FUNKCIJE: sestavni del aminokislin, amidov, proteinov, nukleinskihkislin, nukleotidov, koencimov, heksoaminov, itd.
POMANJKANJE: - pogosto- kloroze predvsem na starih listih- listi postanejo popolnoma rumeni in odmrejo- zaradi tvorbe antocianov lahko purpurna barvastebel in spodnjih strani listov (paradižnik, koruza)
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ATP
ADP + PiH+
2-3 H+
NO3-
redukcija nitrata
NO3- + 8e- + 8H+ → NH3 + 2H2O + OH-
alkalinizacija
OH-
Rizosfera / Apoplast Plazmalema Citosol
NO3- prehrana (sprejem anionov > sprejem kationov)
Agronomija - UNI
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ATP
ADP + PiH+
NH4+
acidifikacija –zakisanje
Rizosfera / Apoplast Plazmalema Citosol
NH4+ prehrana (sprejem kationov > sprejem anionov)
Agronomija - UNI
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NO3-
NH4+
(N2)
aminokislineamidi
peptidiaminiureidi
proteini
nukleinske kisline
drugokoencimisek. produkti...
Agronomija - UNI
Dušik se v rastlini vgrajuje v enostavne in kompleksnejše organske molekule
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Pomanjkanje dušika
Slaba rastKloroze in senescenca, ki napreduje od starejših listov po rastlini navzgorAntociani
Agronomija - UNI
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nitrifikacijadenitrifikacija
nebi
ološ
ka o
ksid
acija
asim
ilatorna redukcija nitrata
organski N
deam
inac
ija
asimil acija am
onija
fiksacija dušika
Kroženje dušika
Agronomija - UNI
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= REDUKCIJA DUŠIKA (NO3- → NH4
+ ) IN NJEGOVA VGRADNJA V ORGANSKE MOLEKULE
Asimilatorna redukcija nitrata
redukcija poteka v dveh stopnjah prva NO3- (nitrat) → NO2- (nitrit) poteka v citosoludruga NO2- (nitrit) → NH4+ (amonij) poteka v citosolu
je energetsko zahtevna: poraba 12 ATP
je zahtevna s stališča porabe reducentov
energijo in reducente zagotavlja proces fotosinteze (fotosintetska redukcija nitrata)
lahko poteka v koreninah ali listih
Agronomija - UNI
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transporter nitrata
plazmalema
vakuola
nitrat reduktaza
nitrit reduktaza
glutamin sintaza / glutamat sintaza
glutamin plastid
Asimilatorna redukcija nitrata
Agronomija - UNI
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NO3-
NO3- + NAD(P)H + H+ + 2e- → NO2
- + NAD(P)+ + H2O
mesto reakcije: citosolencim: nitrat reduktaza,
MoCo encim, regulira ga nivo nitrata, svetloba, ogljikovi hidratiaktivacija z defosforilacijo
Asimilatorna redukcija nitrata
1) nitrat → nitrit
NO2- + 6 Fd red + 8H+ + 6e- → NH4
+ + 6 Fd oks + 2H2O
mesto reakcije: plastidi, kloroplastencim: nitrit reduktaza
2) nitrit → amonij
Agronomija - UNI
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svetloba
svetlob. reakcijefotosinteze
feredoksin(reduciran)
feredoksin(oksidiran)
(Fe4S4) → heme-
nitrit reduktaza
Agronomija - UNI
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0 6 12 18 24
0
2
4
6
0
0.2
0.4
0.6
oo
oo
o
Vse
bnos
t top
nih
ogljik
ovih
hid
rato
v[ %
v s
uhi s
novi
]
-----A
ktivnost nitrat reduktaze[ μg N
O2 -(g sveže m
ase) -1h-1]
Čas [ ure ]
Dnevni hod aktivnosti nitrat reduktaze
Agronomija - UNI
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nitrat reduktaza - protein
nitrat reduktaza - geni
transkripcija
translacija
+
+
+
NO3-
ogljikovi hidrati
svetloba
citokinini
_
glutamin
ABA_
+
Aktivnost nitrat reduktaze uravnavajo različni dejavniki
Agronomija - UNI
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Asimilacija nitrata in njegovo kopičenje
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Rastline, ki jih vzgajamo pri nizkih svetlobnih jakostih (npr. v rastlinjakih pozimi oz. zgodaj spomladi) vsebujejo precej več nitrata kot rastline, ki rastejo ob močnejši svetlobi.
Vzroki:primanjkljaj reducetnovprimanjkljaj ogljikovih skeletovnegativna povratna regulacija – v rastlini se kopičijo aminokisline, ki jih rastlina ne porablja za rast
Nitrat je škodljiv za človeka -pretvorba v NO2
-
→ motnje funkcije hemoglobina (methemoglobinemija)→ kancerogeni nitrozamini
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With a high nitrate supply, and most frequently under low light conditions, lettuce accumulates relatively large amounts of NO3
- as a result of an excess of uptake over reduction. Different approaches, which are used to reduce leaf nitrate, often result in a yield loss. A computerized aeroponic system, which supplies different nitrate concentrations in accordance with the changeable light conditions (dynamic light dependent application of nitrate), was used to reduce nitrate accumulation in lettuce (Lactuca sativa L.) var. Capitata cv. Vanity. Under unfavorable light conditions nitrate was supplied at limited rates (slight-, medium-and strong reduction) to the plants. In response to given light conditions the nitrate supply was reduced close to one-half or one-fourth of the full nutrient solution (8 mmol NO3
- L-1). Controlled nutrition resulted in efficient reduction in leaf nitrate. In the early-spring experiment the average nitrate content in outer leaves was decreased by 9%, 63% and 92% and in the late-spring experiment the decrease was 23%, 58% and 76% compared to control. At the same time the controlled, light dependent nitrate deprivation, did not result in a loss of a lettuce yield (except in the treatment with strong nitrate reduction) and had limited effects on photosynthesis (PN -Ci measurements) and photosynthetic pigments.
DEMŠAR Jernej, OSVALD Jože and VODNIK Dominik (2004)The Effect of Light Dependent Application of Nitrate on the Growth of Aeroponically Grown Lettuce (Lactuca sativa L.).Journal of the American Society for Horticultural Science, 2004
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Računalnik
Aeroponski sistem
Hranilna raztopina
Črpalka
Svetlobni senzor
Krmilna enota
konc. 1 konc. 3 konc. 2 konc. 4
Solati sorte ‘Vanity’ smo v aeroponskem poskusu kontrolirano omejevali dobavo nitrata upoštevajoč svetlobne razmere.
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glutamat + NH4+ + ATP → glutamin + ADP + Pi
(glutamin sintaza)
glutamin + 2-oksoglutarat + NADH + H+ → 2 glutamat + NAD+
(glutamat sintaza)
Amonij NH4+
Vgradnja amonijevega iona
1)
Agronomija - UNI
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GLUTAMIN SINTAZA
GLUTAMAT SINTAZA
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2-oksoglutarat + NH4+ + NAD(P)H ←→ glutamat + H2O + NAD(P)+
(glutamat dehidrogenaza)
glutamat + NH4+ + ATP → glutamin + ADP + Pi
(glutamin sintaza)
glutamin + 2-oksoglutarat + NADH + H+ → 2 glutamat + NAD+
(glutamat sintaza)
Amonij NH4+
1)
2)
Agronomija - UNI
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Glutamat dehidrogenaza
amonij
glutamat2-oksoglutarat
Agronomija - UNI
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transaminacije - sinteza aminokislin, amidov
mesto: citoplazma, kloroplast, mitohondrij, glioksisomi in peroksisomiencimi: aminotransferaze, sintetaze amino kislin
glutamat oksalacetat α-ketoglutarat aspartat
Aspartatna aminotransferaza
Prenos amino skupine ...
Agronomija - UNI
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DUŠIK
BIOLOŠKA (SIMBIOTSKA) FIKSACIJA DUŠIKA
Agronomija - UNI
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biološka fiksacija dušika → 139-170 x 106 ton N leto-1
gnojenje → 65 x 106 ton N leto-1
Haber-Bosch: N2 + 3H2 → 2 NH3 (↑ tlak, ↑ temperatura)
Agronomija - UNI
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N2 + 8e- + 8H+ + 16 MgATP → 2NH3 + H2 + 16 MgATP + 16Pi
encim: nitrogenaza
Reakcijo so sposobni vršiti samo nekateri prokarioti:
simbiotske bakterije
rizosferne bakterije
prostoživeče bakterije
Biološka fiksacija dušika
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tip N-fiksirajoči rod
modrozelene cepljivke (Cyanophyta) Anabaena, Nostoc, Calothrix, Gloeotheca
aerobne bakterije Azotobacter, Azotospirillum, Derxia,Beijerinckia, Bacillus, Klebsiella
anaerobne bakteriije Clostridium, Methanococcus
anaerobne fotoavtotrofne bakterije Chromatium, Rhodospirillum
Prostoživeči fiksatorji dušika
Agronomija - UNI
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fiksiran N
ogljikovihidrati
SIMBIOTSKA FIKSACIJA DUŠIKA
Simbioza = sožitje, oba partnerja imata od zveze korist
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karikatura Dirk Redecker
Agronomija - UNI
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gostiteljska rastlina N-fiksirajoči prokariont
metuljnice AzorhizobiumBradyrhizobiumPhotorhyzobiumRhizobiumSinorhizobium
aktinorizne rastline Alnus (jelša), Ceanothus, Casuarina, Datisca
Frankia
Gunnera Nostoc
Azzola Anabaena
Simbiotski fiksatorji dušika
Agronomija - UNI
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Razvoj simbioze z dušik fiksirajočimi bakterijami
izmenjava signalov med simbiontoma (Nod-geni gostitelja(nodulin)- in nod-geni bakterije (nodulation)migracija bakterij h koreninam (kemotaksija - bekterijeprivlačijo isoflavonoidi in betaini, ki jih izloča rastlinainterakcije oligosaharidov (nod faktor) bakterije in lektinov napovršini koreninskih laskovkodranje koreninskih laskov, vstop bakterij skozi celičnosteno laska in razvoj infekcijske niti, invaginacije plazmaleme, po kateri potujejo bakterije in se delijorazvoj primordija nodula, delitve celic v korteksuko infekcijska nit doseže primordij nodula, se bakterije ovite v fragmente gostiteljeve plazmaleme sprostijo v celiceprimordijadelitev bakterijskih celic, rast, diferenciacija v bakterioide
Agronomija - UNI
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koreninski eksudat
kolonijaizražanje nod genov
receptorji za lektine
pritrditev bakterij, bakterije izločajo signale za kodranje kor. laskov
kodranje kor. laskov
bakterijski signali ali sekund. rastli. signali
razgraditev cel.stene
razvoj infekcijskega
vlakna
vzpodbuditev celičnih delitev v
skorjimeristem nodula
zgodnji razvoj nodula / gomoljčka
flavonoidi in lektini
Bakterije po infekcijskem vlaknu pripotujejo do namnoženih celic skorje,
se v njih sprostijo, so bakterioidi
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RIZOBIJ
INFEKCIJSKA NIT
ZVIJANJE KORENINSKIHLASKOV
BAKTERIOID
Golgi
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Glycine max / Rhizobium japonicum.
Koreninski gomoljček (nodul) je tvorba, ki predstavlja zaščiteno okolje, v katerem lahko bakterija (bakterioid) vrši nitrogenazno aktivnost.
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N2 + 16 ATP + 8e- + 2H+ → NH3 + 16 ADP + 16 Pi + H2
NITROGENAZA
energetsko zahtevenproces redukcija
Fiksacija N2
nfix geni
Agronomija - UNI
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feredoksin(oks.)
feredoksin(red.)
2 NH3, H2
N2, 8H+
NITROGENAZA
Nitrogenaza – encim, odgovoren za fiksacijo N2
Agronomija - UNI
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- Mopodobna slika ob pomanjkanju Co
Mo in Co sta nujno potrebna za normalno delovanje nitrogenaze
Ob pomanjkanju teh dveh mikroelementov rastlina kaže znake pomanjkanja dušika.
Agronomija - UNI
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N2 - substrat
nitrogenaza
amoniak
+ 2H + 2H + 2H
Nitrogenaza ni 100 % specifična
Substrati, ki jih je nitrogenaza sposobna reducirati
Agronomija - UNI
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nitrogenaza je encim, ki je občutljiv na O2
fiksatorji dušika so aktivni v anaerobnih pogojih(zunanjih), ali pa fiksacija dušika poteka v mikroanaerobnih pogojih znotraj samega organizma. Prisimbiotskih fiksatorjih je takšno okolje zagotovljeno z izgradnjo koreninskega gomoljčka
Nitrogenaza je občutljiva na visoke parcialne tlake O2
Agronomija - UNI
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Vzdrževanje majhne koncentracije O2 v nodulih -mehanizmi
debela stena nodula - majhna propustnost za plinesuberin v celični steniprepojitev celičnih sten celic nodula z vodo - vodna oviraza difuzijointenzivna respiracija (dihanje), t.j. poraba kisikavezava O2 na leghemoglobinhem-protein prisoten v citoplazmi inficiranih celic nodula, rožnata barva nodulov, gostitelj proizvaja globin, bakterijapa hem
Agronomija - UNI
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Nitrogenaza: N2 → NH3
zaradi toksičnosti amonijevega iona se ta že v nodulih vgradi v organske molekule, ki služijo za transport v nadzemne dele
Transport fiksiranega dušika iz nodulov
amidi (asparagin, glutamin)
Pisum, Trifolium, Vicia, Lensnoduli imajo nezaključeno rast, nedeterminantni noduli (podolgovati)
Transportne oblike N se razlikujejo v dveh glavnih tipih gomoljčkov
ureidi (alantoin, alantoinska kislina, citrulin)
Glycine, Phaseolus, Arachis, Vignanoduli imajo zaključeno rast, determinantni noduli, okrogli
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Cianobakterije (modrozelene cepljivke) kotfiksatorji dušika
nitrogenaza je aktivna v posebnih celicah, ki jih imenujemoheterociste (celice brez PSII - fotosintetske produkcije O2, z debelimi stenami.
cianobakterije brez heterocist lahko fiksirajo dušik le v anaerobnih pogojih (poplavljenost, riževa polja)
simbiotske povezave cianobakterij in rastlin = sincianoze
Agronomija - UNI
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Heterocista v nitasti cianobakteriji Anabaena. Debela celična stena heterociste predtavlja, poleg nekaterih drugih biokemičnih prilagoditev, mehanizem, s katerim je omogočeno delovanje nitrogenaze. (Taiz & Zeiger, 2002)
Heterocista
Vegetativne celice
Azzola caroliniana s cianobakterijo (Anabaena – A) v votlinici lista (H)
Cianobakterije kot fiksatorji dušika
Agronomija - UNI
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Azolla (vodna praprot) - Anabaena azollae (m.-z. cepljivka)
0.5 kg N ha-1 dan-1
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vrsta mejnevrednosti
povprečnevrednosti
detelja (Trifolium sp.) 45-670 250
grah (Pisum sativum) 50-500 150
lucerna (Medicago sativa) 90-340 250
bob (Vicia faba) 140-200 150
soja (Glycine max) 60-300 100
arašidi (Arachis hypogaea) 50-150 100
leča (Lens culinaris) 50-150 80
fižol (Phaseolus vulgaris) 100-300 200
Fiksacija dušika pri različnih vrstah ( kg N ha-1 leto-1 )
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PRIVZEM: SO42- (aktiven, H-kotransport)
SO2 (skozi listne reže)
ŽVEPLO
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ŽVEPLO
PRIVZEM: SO42- (aktiven, H-kotransport)
SO2 (skozi listne reže)
TRANSPORT:- srednje do težko mobilen element- transport iz korenin v nadzemne dele po ksilemu kot SO4
2-, - po asimilaciji v listih je tranportna oblika za druge dele rastline glutation(tripeptid: glutamat-cistein-glicin), ki se prenaša po floemu
FUNKCIJE: sestavni del aminokislin (cistein, metionin), proteinov, vitaminov (tiamin, biotin), v koencimu A, glutationu itd.
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Spojine, ki vsebujejo žveplo
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Pomanjkanje žvepla
redkosplošne kloroze, na mladih listih, vidne tudi na žilah (t.j po celem listu)
Agronomija - UNI
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= REDUKCIJA SULFATA (SO42- → S2-) IN NJEGOVA VGRADNJA V
ORGANSKE MOLEKULE
Asimilatorna redukcija sulfata
redukcija poteka v dveh stopnjah je energetsko zahtevna: poraba 14 ATP
je zahtevna s stališča porabe reducentov
energijo in reducente zagotavlja proces fotosinteze (fotosintetska redukcija sulfata)
lahko poteka v koreninah ali listih
Agronomija - UNI
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NO3- → NH4
+
npr. glutamat
energija
reducent
NO3-
SO42- → S2-
npr. cistein
SO42- organske S spojine
+ ogljikov skelet
organske N spojine
Agronomija - UNI
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koreninska celica
celica mezofila
Redulcija sulfata v sulfid poteka v plastidih korenin ali nadzemnega dela.
Nereducirani sulfat se lahko shranjuje v vakuolo.
APS = adenozin-P-sulfatPAPS = P-adenozin-P-sulfat
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Aktivacija: pred redukcijo in vgradnjo je potrebna aktivacija sulfata
SO42- + ATP → APS (adenozin-5’fosfosulfat) + PPi
ATP (adenozin-trifosfat)
sulfat
pirofosfat
APS (adenozin-5'-fosfosulfat)
ATP sulfurilaza
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(1) APS + 2GSH → SO32-
(sulfit) + 2H+ + GSSG + AMP
Agronomija - UNI
Redukcija sulfata
je večstopenjski proces, ki poteka v plastidih
APS reduktaza
reduciran glutation
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reduciranglutation
oksidiranglutation
glutationreduktaza
Glutation
Agronomija - UNI
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(1) APS + 2GSH → SO32-
(sulfit) + 2H+ + GSSG + AMP
(2) SO32-
(sulfit) + 6 Fdred → S2-(sulfid) + 6 Fdox
Agronomija - UNI
Redukcija sulfata
je večstopenjski proces, ki poteka v plastidih
APS reduktaza
reduciran glutation
sulfit reduktaza
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O-acetilserin + S2- → cistein + acetat
Nastanek cisteina in prenos SH- skupine ...
Agronomija - UNI
cistein + O-fosfohomoserin →→→ metionin
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Agronomija - UNI
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FOSFOR
PRIVZEM: H2PO4- (aktiven, H-kotransport)
HPO42- (aktiven, H-kotransport), manj mobilen
pH < 7 pH > 7H2PO4
- HPO42-
TRANSPORT:- dobro mobilen element, - skladiščenje v obliki polifosfata (linearno vezani Pi), fitinska kislina
FUNKCIJE: fosfati sladkorjev, nukleinske kisline, nukleotidi, koencimi, fosfolipidi, fitat, ključna vloga pri ATP
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Pomanjkanje fosforja
pogosto
listi majhni, temno zeleni
pojav rdeče in škrlatne barve(antociani)
stebla nizka in vitka
Agronomija - UNI
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Fosfor se v rastlini ne reducira
Nahaja se v obliki fosfata ali vezan (zaestren) v organskih spojinah
Pi
C - O - P, C - P - C
fitinska kislina = mioinozitol + 6 P
Agronomija - UNI
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encim - Pencim
X − P X
Pi H2O
KINAZA
FOSFATAZA
kalmodulin
X = npr. ATP
(Ca 2+ )
S fosforilacijo (defosforilacijo) je uravnavana aktivnost encimov
Agronomija - UNI
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MIKORIZA
FOSFOR
Agronomija - UNI
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karikatura Dirk Redecker
Agronomija - UNI
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ogljikovihidrati
fosfor in drugamineral. hranila
Mikoriza
Agronomija - UNI
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EKTOTROFNA ENDOTROFNA
• EKTOMIKORIZA • ARBUSKULARNA MIKORIZA• ERIKOIDNA MIKORIZA• ORHIDEJSKA MIKORIZA
EKTENDOTROFNA MIKORIZA• ARBUTOIDNA MIKORIZA• MONOTROPOIDNA MIKORIZA• EKENDOMIKORIZA
MIKORIZA
Agronomija - UNI
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TIPI MIKORIZE
• ENDOTROFNA MIKORIZA - gliva vstopa v celice• EKTOTROFNA MIKORIZA - gliva se nahaja zunaj celice
tip AM ECM Ektendo- Arbutoidna
Mono-tropoidna
Erikoidna Orhidejska
septirane hife - (+) + - + - + + + +hife v celicah + - + + + + +zvitki hif + - - - - - + +arbuskuli + - - - - - -hifni plašč - + (-) + (-) + + - -Hartigova mreža - + + + + - -vezikli + - - - - - - -
Rastline vaskularnerastline
golosemenke inkritosemenke.
Ericales Mono-tropaceae
Ericales Orchid-aceae
klorofil + + + + - - + + -
Glive Zygo-Glomales
Basidio –, Asco-Zygomycetes,
Asco-Basidio-mycetes
Basidio-mycets
arbuskularna ektomikoriza
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Prevladujoča oblika dušika Organski N NH4
+ NO3-NH4
+ + NO3-
Karakteristični tip mikorize Erikoidna Ektomikoriza
Arbuskularnamikoriza
Ekto- + arbuskularna
mikoriza
Deficitarno hranilo N N ali P P
Porast nadmorske višine ali zemljepisne širine
Količina in lastnosti
vegetativnega micelija gliv
Fine posamezne hife poleg
površja korenin, biomasa mala
Ekstenzivni micelij, združevanje hif v
snope, velika biomasa
Posamezne hifevečjega premera,
biomasa velika tik ob koreninah
Količina organske snovi
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Smith and Read, 1997
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ektomikorizni gostitelji14 družin, 62 rodov
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EKTOMIKORIZA - prerez korenine
Hartigova mreža
hifni plašč
Agronomija - UNI
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ekstramatrikalni micelij
skorja = korteks
centralni cilinder
tla
korenina
Arbuskularna mikoriza
spora
arbuskulvezikel
Agronomija - UNI
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Arbuskularna mikoriza - ARBUSKULI
Agronomija - UNI
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Klasifikacija AM gliv
GLOMALES
GIGASPORINAEGigasporaceae
GigasporaScutellospora
GLOMINEAEGlomaceae
GlomusSclerocystis
AcaulosporaceaeAcaulosporaEntrophospora
(Morton & Benny 1990)
Agronomija - UNI
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Prednosti mikoriznih rastlin
izboljšana mineralna prehranapovečan volumen tal, v katerem lahko rastlina izkoriščahranilapovečana razpoložljivost hranil zaradi glive(mobilizacija), shranjevanje
izboljšana preskrba z vodo
povečana odpornost na abiotski stres (suša, težkekovine, organski toksini)
povečana odpornost na patogene in herbivore (npr. nematodi)
Agronomija - UNI
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Mikoriza in absorpcija hranil in vode
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Biotehnološka uporaba mikorize
izolacija glivpridobivanje glivnega inokulumainokulacijafiziološki odgovor inokuliranih rastlin (rast, pridelek)selekcijaprenos v prakso
Agronomija - UNI
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MAGNEZIJ
PRIVZEM: Mg2+
↓ ← K+, NH4+, Ca2+, Mn2+
TRANSPORT: dobro mobilen
FUNKCIJE:
sestavni del klorofilaaktivacija encimov udeleženih v respiraciji in fotosintezi ter sintezi DNA in RNAMg-ATPskupaj s Ca2+ stabilizira strukture v ribosomihpektati v osrednji lameli...
klorofil a
Agronomija - UNI
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Pomanjkanje Mg pri paradižniku
Pomanjkanje Mg
najprej kloroze starejših listovnajpogosteje kloroze med žilamilahko predčasno odpadanje listov
Agronomija - UNI
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KALCIJ
PRIVZEM: Ca2+
TRANSPORT: zelo slabo mobilen v ksilemu in floemu
NAHAJANJE: veliko Ca v apoplastu (za razliko od drugih elementov)zelo majhna koncentracija Ca2+ v citosolu (0.1-0.2 μM), velike koncentracije v vakuoli in endoplazmatskemuretikulumu
membrana je nepropustna za Ca2+ ,potreben je aktiven transport, velika potreba po energijiCa2+ črpalke
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celična stena
osrednja lamela
plazmalema
citoplazma
vakuola
endoplazmatskiretikulum
Razporeditev Ca v celici in celični steni
Ioni Ca2+ so prikazani s črnimi krožci
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Celični transport Ca2+
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Ca2+ kot sekundarni sporočevalec
Prikaz vdora kalcijevih ionov skozi kanalčke v celico, kot posledica zaznave signala na plazmalemi.
Posledica je lokalno povečana koncentracija Ca2+ v citosolu, ki pomeni za celico informacijo, ki proži odgovor.
citosol
plazmalema
celična stena
R receptor
SIGNAL
+
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svetloba, temperaturahormoniranitevdrugo
signal
celična stena(apoplast)
plazmalema
citoplazma
inozitol 1,4,5trifosfat
vakuola
proteinkinaza
(akt.)fosforilacijaproteinov fiziološki odgovor
1,4 glukansintaza
1,3 glukansintaza
kalmodulin
celuloza kaloza
Ca2+ kot sekundarni sporočevalec
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stabilizacija celične stenestabilizacija membrane - povezovanjefosfatnih in karboksilnih skupin v fosfolipidihrast celicsekrecija, eksocitozaravnotežje kationi: anioniosmoregulacijasekundarni sporočevalec - prenos signala v celici…
Funkcije kalcija
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poškodbe meristematskih tkivnagubani roboviob robovih navzgor zavihani listikloroze in nekroze najmlajšihlistov in vršičkov
Pomanjkanje kalcija
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KALIJ
PRIVZEM: K+ (aktiven, pasiven)
kation z največjo koncentracijo v citoplazmi (100-200 mM), podobnakoncentracija K+ je v kloroplastu
ASIMILACIJA: tvori šibke komplekse,iz katerih se z lahkoto izmenjuje
TRANSPORT: je dobro mobilen (celica, tkivo, cela rastlina)
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nevtralizacija topnih in netopnih anionov in stabilizacija pH (med (7.0 in 8.0), vzdrževanje ravnotežja med kationi in anioniaktivacija encimov (optimalen hidratacijski ovoj - aktivnost)aktivacija H+-ATPaze na plazmalemipomemben pri sintezi proteinovfotosinteza - vzdrževanje protonskega gradienta na tilakoidnimembraniosmoregulacijacelična rast (sodeluje pri spremembah turgorja = potencialatlaka)pomemben pri rastlinskih gibanjihpomemben pri polnjenju floema
Funkcije kalija
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mehanizem odpiranja/zapiranja je sprememba Ψs (črpanje K+ v celico) in posledično sprememba Ψp v celicah zapiralkah)
Kalij je pomemben pri regulaciji transpiracije
↑[K+] v celici → ↓Ψs→ ↑ΨP→ odprtje reže ↓[K+] v celici → ↑Ψs→ ↓ΨP→ zaprtje reže
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Pomanjkanje K
nekroze na listnih konicah in robovih
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Privzem: helati Fe3+ , Fe2+
ŽELEZO
Agronomija - UNI
Transport
Fe(II)-helat, Fe(II) citratmobilnost v rastlini je slabanajveč železa se nahaja v kloroplastih hitro rastočih listovfitoferitin - skladiščna oblika železa
Funkcije železa
redoks funkcija Fe(III) + e- ↔ Fe(II)citokrom (redoks reakcije v kloroplastih in mitohondrijih) železovo žveploviproteini (feredoksin) in drugi Fe-proteininujno za sintezo klorofila in razvoj kloroplastov
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Pomanjkanje Fe
problematično predvsem na karbonatnih tlehrumenenje oz. bledenje mladih listovprezgodnje odpadanje listov
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Dostopnost železa v raztopini je pogostokrat majhna zaradiprecipitacije (tvorba železovega hidroksida ob prisotnosti sulfatov in nitratov, tvorba železovega fosfata)
Helatorji: organske snovi, kitvorijo z Fe komplekse in gasprostijo v raztopino (citrat, EDTA, DTPA)
Slika: DTPA (dietilentriaminpentaocetna kislina)
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Ob pomanjkanju železaje inducirano delovanjereduktaze, ki reduciraFe(III) helate, sproščenoFe(II) se transportirapreko plazmaleme s prenašalnim proteinomvisoke afinitete. Hkrati jeintenzivnejšo tudidelovanje H+-ATPaze, kizakisa rizosfero in poveča topnost železa.
Privzem železa - strategija I (dvokaličnice in enokaličnice - razen trav)
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Ob pomanjkanju železa je indukcije Fe(III)-reduktaze in prenašalca za Fe(II) vzpodbujeno tudi delovanje protoinske črpalke (H+-ATPaze), ki zakisarizosfero (rumen oz. rdeč indikator na slikah B in D).
Privzem železa - strategija I (dvokaličnice in enokaličnice - razen trav)
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1 -sinteza fitosiderofor; 2, 3- membranski transportni proteini, katerih delovanjeje ob pomanjkanju železa inducirano
Privzem železa - strategija II (trave)sinteza in sproščanje siderofor - neproteinogenih aminokislin, ki so helatorji Fe
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Siderofori
mugineinska kislina
Neproteinogene aminokisline, ki helirajo železo
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PRIVZEM: helati Fe3+ , Fe2+
mehanizem 1 (dvokaličnice in enokaličnice, brez trav)
povečana aktivnost protonske črpalke na plazmalemiprotoni stimulirajo reduktazo, encim na zunanji strani plazmalemehelatorji vežejo Fe(III), ga prinesejo do reduktaze, ki železo reducira v Fe(II)transportni protein prenese Fe(II) v celicoanatomske spremembe rizodermalnih celic
mehanizem 2 (trave)
povečano izločanje neproteinogenih aminokislin FITOSIDEROFORfitosiderofore helirajo železo Fe(III)helirano Fe(III) se s posebnim transportni proteinom prenese v celico
ŽELEZO
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PRIVZEM: B(OH)3
pH < 7 B(OH)3
pH > 7 B(OH)4-
FUNKCIJE: - kompleksi z organskimi spojinami- celična stena- rast korenin- metabolizem nukleinskih kislin- metabolizem ogljikovih hidratov in proteinov
TRANSPORT: - ksilem, transpiracijski tok- mobilnost slaba -
BOR
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kompleksi bora z organskimi spojinami
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Pomanjkanje bora pri cvetači
Pomanjkanje bora pri detelji
Pomanjkanje B
pogostokloroze in odmiranje najmlajšihlistov in terminalnih brstovkrajši internodijidebelejši peclji in stebla –pokanje“black heart”
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PRIVZEM: Zn2+
ZnOH+ (visok pH)
FUNKCIJE:- kompleksi z organskimi spojinami (z N-, O- in S-ligandi)- katalitična in strukturna vloga v encimih (npr. alkoholna dehidrogenaza, karbonska anhidraza, superoksid dismutaza, idr.)- struktura proteinov- metabolizem nukleinskih kislin- metabolizem ogljikovih hidratov (aldolaza, fruktoze 1,6-bifosfataza)- sinteza avksinov- ...
TRANSPORT: - ksilem, transpiracijski tok, cink vezan na organske molekule- floem
CINK
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karbonatna tlarozetavost, krajši internodiji (↓ avksin)kloroze nekroze (sek. znaki)
Pomanjkanje Zn
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Mangan
- Mn2+ je aktivator encimov npr. encimov Krebsovega cikla(dekarboksilaze, dehidrogenaze)- sodeluje v fotolizi vode (sproščanje O2 v procesu fotosinteze)Pomanjkanje se kaže v obliki medžilni kloroz in pegastih nekroz
Baker
- Cu2+ ↔ Cu+
- udeležen v redoks reakcijah - prenosu elektrona (npr. platocianin-svetlobne reakcije fotosinteze)Pomanjkanje se kaže v obliki točkastih nekroz na konicah listov, listiso temno zeleni
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Molibden
- Mo4+, Mo6+
- sestavni del več encimov (nitrat reduktaza, nitrogenaza)Pomanjkanje se kaže kot splošna kloroza in nekroza starejših listov, listiso lahko deformirani
Natrij
- pomemben v metabolizmu C4 in CAM rastlin, regeneracija- kot osmotik lahko delno nadomesti kalij
Klor
- Cl-, fotoliza vode, celične delitve
Nikelj
- v encimu ureaza
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