The role of mmoni in plnt physiology Ineke Stulen, An Cstro, nd Luit J. De Kok Lortory of Plnt Physiology University of Groningen The Netherlnds
N is essentil mino cids nd proteins
N uptke nd ssimiltion NH 3 nitrte mmonium
N ssimiltion - root NO 3- nd NH 4 + ctively tken up y trnsporters nitrte mmonium
N ssimiltion - root NO 3- nd NH + 4 ctively tken up y trnsporters NO 3- reduced, nd trnsported nitrte mmonium
N ssimiltion - root NO 3- nd NH + 4 ctively tken up y trnsporters NO 3- reduced, nd trnsported NH + 4 ttched to C skeleton (GS) nitrte mmonium
N ssimiltion - root nitrte mmonium NO 3- nd NH + 4 ctively tken up y trnsporters NO 3- reduced, nd trnsported NH + 4 ttched to C skeleton (GS) mino cids formed used in protein synthesis
N ssimiltion - lef NO 3- reduced NH 4 + ttched to C skeleton
N ssimiltion - lef NO 3- reduced NH 4 + ttched to C skeleton mino cids formed used in protein synthesis
Atmospheric NH 3 deposition NH 3 tken up dissolved in poplst NH 4+ formed NH 4 + ssimilted y glutmine synthetse(s)
Atmospheric NH 3 deposition NH 3 tken up dissolved in poplst NH 4+ formed NH 4 + ssimilted y glutmine synthetse(s) M. Pérez-So, 1995
Atmospheric NH 3 s N source proteins mino cids NH 3 sustomtl cvity mesophyll GOGAT GS NH 4 + GS - glutmine synthetse high ffinity for NH 4 +
Atmospheric NH 3 s N source underlying physiologicl processes series of experiments with Brssic olerce (curly kle) exposed to rnge of NH 3 concentrtions (0-8 µl l -1 ) for one week controlled environmentl conditions in nutrient solution, with nd without nitrte
Atmospheric NH 3 s N source underlying physiologicl processes contriution to the N requirement for growth? effect on root NO 3+ uptke? A. Cstro, 2006
Atmospheric NH 3 s N source underlying physiologicl processes [N] μmolg -1 FW 1250 1000 750 500 250 Totl nitrogen content c d Increse in totl N nd mino cids up to the highest [NH 3 ] Plnts grown with nitrte in the nutrient solution 0 0.0 2.0 4.0 6.0 8.0 μmol g -1 FW 125 100 75 50 25 0 Free mino cid content d c 0.0 2.0 4.0 6.0 8.0 [NH 3 ] μl l -1 Metolic detoxifiction cpcity of the GS/GOGAT system to ssimilte NH 4+ - is high over the whole rnge
Atmospheric NH 3 s N source underlying physiologicl processes [N] μmolg -1 FW 1250 1000 750 500 250 Totl nitrogen content c d gfw 7.5 5.0 2.5 Increse in fresh weight / 7 dys c 0 0.0 2.0 4.0 6.0 8.0 0.0 0.0 2.0 4.0 6.0 8.0 [NH 3 ] μl l -1 μmol g -1 FW 125 100 75 50 25 0 Free mino cid content d c 0.0 2.0 4.0 6.0 8.0 [NH 3 ] μl l -1 growth (increse in fresh weight) is reduced t 6 nd 8 µl l -1 NH 3 lthough detoxifiction is still possile, shoot nd root growth re reduced!
Atmospheric NH 3 s N source contriution to N nutrition Control 4 μl l -1 NH 3 + NO 3 - -NO 3 - + NO 3 - -NO 3 - Biomss S 1.19 c 0.29 1.17 c 1.03 c Biomss R 0.24 0.35 cd 0.10 0.35 cd DW % S 8.9 17 d 12 c 12 Totl N S 618 c 414 917 e 803 d AA S 14 9 73 d 64 d Totl N R 317 c 202 348 c 339 c AA R 11 13 24 c 25 c Experiments with B. olerce, grown in nutrient solution, + nd NO 3-, fumigted with 4 µl l -1 NH 3 (Cstro, 2006) S shoot; R root; iomss production in g; N nd mino cids (AA) in µmol g -1 FW Plnts cn grow well with NH 4+ s sole N source
Atmospheric NH 3 s N source contriution to N requirement for growth N requirement for growth cn e defined s N requirement = (RGR) x N content in which RGR is the reltive growth rte g g -1 dy -1 4 µl l -1 NH 3 s sole N source cn contriute considerly (70-80%) to the N requirement for growth in greement with theoreticl clcultions (Stulen et l, 1998) nd Rven (1998)
Atmospheric NH 3 s N source effect on root uptke Does fumigtion with 4 µl l -1 NH 3 reduce root NO 3- uptke? reduced N compound Root NO 3- uptke
Atmospheric NH 3 s N source effect on root uptke Does fumigtion with 4 µl l -1 NH 3 reduce root NO - 3 uptke? 150 125 100 75 50 25 c () 0 75 60 c 45 30 15 0 0 0 4 8 [NH 3 ] μl l -1 signl specific AA 15 N Nitrte uptke rte (μmol g -1 FW dy -1 ) Net nitrte uptke rte (μmol g -1 FW dy -1 ) 30 () 24 18 12 6 Net sulphte uptke rte (μmol g -1 FW dy -1 ) 0 4 8 [NH 3 ] μl l -1
Atmospheric NH 3 s N source underlying physiologicl processes contriution to the N requirement effect on root uptke nutrient vs toxin? oth mechnisms of NH + 4 toxicity?
Atmospheric NH 3 proposed mechnisms of toxicity evidence? 1. Insufficient detoxifiction cpcity no evidence 2. Shortge of sugrs?
Atmospheric NH 3 shortge of sugrs? 6 () Shoot solule sugr (μmol g -1 FW) Root solule sugr (μmol g -1 FW) 5 4 3 2 1 0 2.0 1.5 1.0 0.5 0.0 c c c c 0 4 8 () The impct of NH 3 on solule sugr content in shoot () nd roots (). + NO 3 - nd NO 3 - tretments re given in drk nd light-grey rs, respectively. [NH 3 ] μl l -1 2. Shortge of sugrs? no evidence
Atmospheric NH 3 proposed mechnisms of toxicity 1. Insufficient detoxifiction cpcity no evidence 2. Lck of sugrs for the ssimiltion of NH 4 + no evidence 3. Ction imlnces impired root uptke? 4. Ethylene response soil/root comprtment experiments in nutrient solution [NH 3 ] 0 8 µl l -1 yerly verge concentrtion: 6.6 µg m 3 9.3 nll -1 5.1 µg m 3 8.0 nl l -1 pek concentrtions: > 2 µl l -1
Atmospheric NH 3 nutrient or toxin? nutrient detoxifiction inhiition of growth toxin grdul - depending on plnt species
The role of NH 3 in plnt functioning With the current knowledge on the impct of tmospheric NH 3 on plnt functioning it is hrd to estlish cuse-effects reltions. The physiologicl sis the phytotoxicity of tmospheric NH 3 is still lrgely unknown. There is no cler-cut trnsition in the level of metolism of the sored tmospheric NH 3 nd its phytotoxicity. The effect of tmospheric NH 3 on plnts might e strongly dependent on the soil nutrient sttus.
The role of NH 3 in plnt functioning With the current knowledge on the impct of tmospheric NH 3 on plnt functioning it is hrd to estlish cuse-effects reltions. The physiologicl sis of the phytotoxicity of tmospheric NH 3 is still lrgely unknown. There is no cler-cut trnsition in the level of metolism of the sored tmospheric NH 3 nd its phytotoxicity. The effect of tmospheric NH 3 on plnts might e strongly dependent on the soil nutrient sttus.
The role of NH 3 in plnt functioning With the current knowledge on the impct of tmospheric NH 3 on plnt functioning it is hrd to estlish cuse-effects reltions. The physiologicl sis of the phytotoxicity of tmospheric NH 3 is still lrgely unknown. There is no cler-cut trnsition in the level of metolism of the sored tmospheric NH 3 nd its phytotoxicity. The effect of tmospheric NH 3 on plnts might e strongly dependent on the soil nutrient sttus.
The role of NH 3 in plnt functioning With the current knowledge on the impct of tmospheric NH 3 on plnt functioning it is hrd to estlish cuse-effects reltions. The physiologicl sis of the phytotoxicity of tmospheric NH 3 is still lrgely unknown. There is no cler-cut trnsition in the level of metolism of the sored tmospheric NH 3 nd its phytotoxicity. The effect of tmospheric NH 3 on plnts might e strongly dependent on the soil nutrient sttus.