Ý- :
N2 (NH3,NOX) (NO3‾,NH4+) ( ---) . . . nitrification .
5. 10 10 1000 . . . PH . . NH3 NO2 . . . (cation/anion balanced) . .
ȝ- :
. , . 70 80% . . . . .
- :
13N-or 15N-labelled NO3- Hydroponically cultured plants . high and low affinity transport system . HATS 100-200M . Km 7-100M . 200M LATS Km ,5M . HATS LATS .(Km Vmax )
. . 6 12 . .
Vmax . . . NO2- NH4+AA .
.
- :
. crnA NRT2 CHL1 NRT1 . .
(1) (HATS):
NRT2 , (HA uptake) . . . .
(2) (LATS) :
Arabidopsis chlorate . nitrate reductase chlorite .
. T-DNA , . . . . LeNRT1-1 &1-2 88% Arabidopsis , . (LATS) .
- :
strong negative down-regulation (HATS) . . HATS LATS . / . . depolarized HATS 4.5-9 . , .
- :
. , ammonification nitrification . , . . .
. Brassica C/N .
:
2-6% . . . +5 -3 . . .
:
( , , ) () . . .
.
NH4+--------->NH2OH------->[HNO]----------->NO2------------>NO3-
. . .
(nitrate reductase):
1 30 . :
** .
** .
** nitrate reductase .
( NO-3) -3 (NH+4) 8 20% . , cytotoxin . (N.R) . . . . .
. . . nitrate reductase .
:
. . feredoxin . :
NO2- + 6Fdred + 8H+------------------------------------->NH4+ + 6Fdox +2H2O
NADPH feredoxin .
NO2- + 3NADPH + 5H+------------------------------------->NH4+ + 3NADP+ +2H2O
( ) .
() N.R . . ( ) .
:
( ) . :
1-
2- .
. . .
:
. : . 1-2 ATP . . . ATPase-H+ .
:
. . () . Gln synthetase . . . . . . .
: .
. .
:
. .
.