ASSIMILATION OF MINERAL NUTRIENTSASSIMILATION 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 TOXICITYAMMONIA TOXICITY

NITRATE REDUCTASE REACTIONNITRATE REDUCTASE REACTION

NONO33-- + NAD(P)H + H + NAD(P)H + H++ + 2e + 2e-- NO NO22

-- + NAD(P) + NAD(P)++ + H + H22OO

INDUCTION OF NITRATE REDUCTASEINDUCTION OF NITRATE REDUCTASE

NITRITE REDUCTASE REACTIONNITRITE REDUCTASE REACTION

NONO22-- + 6Fd + 6Fdredred + 8H + 8H++ + 6e + 6e-- NHNH44

++ + 6Fd + 6Fdoxox + 2 H + 2 H22OO

• PLANTS CAN ASSIMILATE NITRATE IN BOTH ROOTS AND PLANTS CAN ASSIMILATE NITRATE IN BOTH ROOTS AND SHOOTSSHOOTS

FORMS OF NITROGEN IN XYLEM SAPFORMS OF NITROGEN IN XYLEM SAP

CONVERSION OF AMMONIUM TO AMINO ACIDS CONVERSION OF AMMONIUM TO AMINO ACIDS REQUIRES TWO ENZYMESREQUIRES TWO ENZYMES

(GOGAT)(GS)(GS)

GDH PATHWAYGDH PATHWAY

ASPARTATE FORMATION - TRANSAMINATIONASPARTATE FORMATION - TRANSAMINATION

ASPARAGINE SYNTHESISASPARAGINE SYNTHESIS

SUMMARY OF PROCESSES INVOLVED IN ASSIMILATION SUMMARY OF PROCESSES INVOLVED IN ASSIMILATION OF MINERAL NITROGEN (Leaf)OF MINERAL NITROGEN (Leaf)

“Photoassimilation”

BIOLOGICAL NITROGEN FIXATIONBIOLOGICAL NITROGEN FIXATION

ANABAENA (CYANOBACTERIUM)ANABAENA (CYANOBACTERIUM)

SOYBEAN SOYBEAN ROOT ROOT

NODULESNODULES

Development of infection threadDevelopment of infection thread

Root Nodule DevelopmentRoot Nodule Development

Leghemoglobin

Isoflavonoids, betaines

NOD FACTORS PRODUCED BY BACTERIA ACT AS NOD FACTORS PRODUCED BY BACTERIA ACT AS SIGNALS FOR SYMBIOSISSIGNALS FOR SYMBIOSIS

NOD FACTORS ARE LIPOCHITIN OLIGOSACCHARIDESNOD FACTORS ARE LIPOCHITIN OLIGOSACCHARIDES

THE NITROGENASE REACTIONTHE NITROGENASE REACTION

(oxygen-sensitive)(oxygen-sensitive)

N2 + 8 e- + 8 H+ + 16 ATP

2 NH3 + H2 + 16 ADP + 16 Pi

AMIDES (ASPARAGINE AND GLUTAMINE) AND UREIDES AMIDES (ASPARAGINE AND GLUTAMINE) AND UREIDES ARE THE TRANSPORTED FORMS OF NITROGEN IN ARE THE TRANSPORTED FORMS OF NITROGEN IN

LEGUMESLEGUMES

UREIDESUREIDES

EXAMPLES OF COORDINATION COMPLEXESEXAMPLES OF COORDINATION COMPLEXES

ELECTROSTATIC IONIC COMPLEXESELECTROSTATIC IONIC COMPLEXES

FERROCHELATASE REACTIONFERROCHELATASE REACTION

EXAMPLES OF OXYGENASE REACTIONS IN PLANTSEXAMPLES OF OXYGENASE REACTIONS IN PLANTS