The effects of pre-treat with Mo on the nr of wheat leaves(Randall, 1969) Mo supply in Pre-treat of NR activity(umolNO2 /gFW) the plant leaves growth 24h 70h (ug/plant (ugMO/L) 0.005 0.2 0.3 0.005 100 2.8 5.0 8.0 5.0 100 8.2
The effects of pre-treat with Mo on the NR of wheat leaves (Randall，1969） Mo supply in the plant growth （µg/plant） Pre-treat of leaves （µgMo/L） NR activity（µmolNO2 - /gFW） 24h 70h 0.005 0 0.2 0.3 0.005 100 2.8 4.2 5.0 0 / 8.0 5.0 100 / 8.2
Site of nitrate reduction in plant Although most of plant species are able o reduce no both in the roots and the shoots, there is differs between species Most of nitrate is reduced in trees and shrub roots NO3 reduction must take place primarily in green plant part in tomato Oats>maize>sunflower>barley> oil radish Root → shoot
Site of nitrate reduction in plant ▪ Although most of plant species are able to reduce NO3 - both in the roots and the shoots, there is differs between species. ▪ Most of nitrate is reduced in trees and shrub’ roots . ▪ NO3 - reduction must take place primarily in green plant part in tomato. ▪ Oats>maize>sunflower>barley>oil radish ▪ Root ----------------------------------→shoot
Nitrite reduction Light H (reduced) Nitrite Light Reactions in Photosynthesis (Fe4S4)→Heme H Ferredoxin y trite reducta Ammonia (oxidized)
Nitrite reduction
Nitrite reduction in the chloroplast In chloroplast, No2 is reduced by the nitrite reductase which is probably located at out side of the thylakoid(类囊体) membrane and thus may directly accept the e- from ferredoxin(铁氧还蛋白) which in turn receives e from photosystem I NO2+ 6Fdred 8H+-->NH4 6Fdox +2H2O There is thus a direct relationship between photosynthetic activity and nitrite reduction
In chloroplast, NO2 - is reduced by the nitrite reductase which is probably located at out side of the thylakoid(类囊体） membrane and thus may directly accept the e - from ferredoxin（铁氧还蛋白） which in turn receives efrom photosystem І. ▪ NO2 - + 6Fdred + 8H+ --->NH4 + + 6Fdox +2H2O ▪ There is thus a direct relationship between photosynthetic activity and nitrite reduction. Nitrite reduction in the chloroplast
Nitrite reduetion in plastids(质体) Nitrite is also reduced in plastids of root where ferredoxin-like e carrier enzyme transfer e from NADPH to nitrite reductase NO.+ 3NADPH 5H+--->NH+ 3NADP+ +2H.O The synthesis of nitrite reductase is induced by nitrite as well as by nitrate Nitrite reductase activity is also dependent on the supply of photosynthesis
Nitrite reduction in plastids(质体） ▪ Nitrite is also reduced in plastids of root where ferredoxin-like e- carrier enzyme transfer efrom NADPH to nitrite reductase. ▪ NO2 - + 3NADPH + 5H+ --->NH4 + + 3NADP+ +2H2O ▪ The synthesis of nitrite reductase is induced by nitrite as well as by nitrate. ▪ Nitrite reductase activity is also dependent on the supply of photosynthesis