ASSIMILATION OF MINERAL NUTRIENTS
• NUTRIENT ASSIMILATION: THE INCORPORATION OF MINERAL
NUTRIENTS INTO ORGANIC COMPOUNDS.
• ASSIMILATION OF SOME NUTRIENTS—PARTICULARLY NITROGEN
AND SULFUR—REQUIRES A COMPLEX SERIES OF BIOCHEMICAL
REACTIONS.
• ASSIMILATION OF OTHER NUTRIENTS INVOLVES THE FORMATION
OF COMPLEXES WITH ORGANIC COMPOUNDS (e.g. Mg2+
ASSOCIATION WITH CHLOROPHYLL).
AMMONIA TOXICITY
NITRATE REDUCTASE REACTION
NO3- + NAD(P)H + H+ + 2e-  NO2- + NAD(P)+ + H2O
INDUCTION OF NITRATE REDUCTASE
NITRITE REDUCTASE REACTION
NO2- + 6Fdred + 8H+ + 6e- NH4+ + 6Fdox + 2 H2O
• PLANTS CAN ASSIMILATE NITRATE IN BOTH ROOTS AND
SHOOTS
FORMS OF NITROGEN IN XYLEM SAP
CONVERSION OF AMMONIUM TO AMINO ACIDS
REQUIRES TWO ENZYMES
(GS)
(GOGAT)
GDH PATHWAY
ASPARTATE FORMATION - TRANSAMINATION
ASPARAGINE SYNTHESIS
SUMMARY OF PROCESSES INVOLVED IN ASSIMILATION
OF MINERAL NITROGEN (Leaf)
“Photoassimilation”
BIOLOGICAL NITROGEN FIXATION
ANABAENA (CYANOBACTERIUM)
SOYBEAN
ROOT
NODULES
Development of infection thread
Root Nodule Development
Isoflavonoids,
betaines
Leghemoglobin
NOD FACTORS PRODUCED BY BACTERIA ACT AS
SIGNALS FOR SYMBIOSIS
NOD FACTORS ARE LIPOCHITIN OLIGOSACCHARIDES
THE NITROGENASE REACTION
(oxygen-sensitive)
N2 + 8 e- + 8 H+ + 16 ATP 
2 NH3 + H2 + 16 ADP + 16 Pi
AMIDES (ASPARAGINE AND GLUTAMINE) AND UREIDES
ARE THE TRANSPORTED FORMS OF NITROGEN IN
LEGUMES
UREIDES
EXAMPLES OF COORDINATION COMPLEXES
ELECTROSTATIC IONIC COMPLEXES
FERROCHELATASE REACTION
EXAMPLES OF OXYGENASE REACTIONS IN PLANTS