Photosynthesis sensitivity to NH 4 + -N change with nitrogen fertilizer type

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1 Vol. 6, 214, No. 6: Plnt Soil Environ. Photosynthesis sensitivity to -N hnge with nitrogen fertilizer type A. Nsroui-Hjji, H. Goui Reserh Unit of Nitrogen Nutrition n Metolism n Stress-relte Proteins (99/UR/C 9-2), Tunisin Fulty of Sienes, University of Tunis El Mnr, El Mnr, Tunisi ABSTRACT N-fertiliztion type ffete ifferently tomto growth. In the fiel experiment, hyroponi ultures were onute using NO 3 -N (5 mmol); mixture of KNO 3 -N (3 mmol) n ( ) 2 SO 4 -N (2 mmol); -N (5 mmol) or ure (5 mmol) s nitrogen soure. Compre to nitrte, mmonium n ure h negtive effets on morphology n ry mtter proution. Effets of the ifferent nitrogen forms were investigte y mesuring severl photosynthesis prmeters n hl fluoresene. Two ifferent signifint types of retion were foun. When nitrogen ws e s mmonium or ure, ry weight, hlorophyll tenor, trnspirtion rte, stomtl onutne n photosyntheti tivity were inhiite. Supply of mmonium or ure, reue the rtio (F v ), photohemil quenhing n enhne the non photohemil quenhing. These t suggest tht the verse erese in tomto growth uner mmonium or ure supply my e relte priniplly to inhiition of net photosynthesis tivity. The high non photohemil quenhing shown in tomto fe with mmonium or ure inite tht PS II ws the inhiitory site of -N whih ws iretly uptken y roots, or lirte vi ure hyrolysis yle. Keywors: mmonium; hlorophyll fluoresene; gs exhnge; tomto; Solnum lyopersion Plnts n use vrious forms of nitrogen from soils, most importntly the inorgni ions mmonium ( ) n nitrte (NO 3 ). Nevertheless, ure onstitutes nother nitrogen soure wiely use y plnts. In ft to provie rops proution ure is intensively use s nitrogen fertilizer. Ure nitrogen enters the plnt either iretly, or in the form of mmonium or nitrte fter ure egrtion (Byrnes n Freney 1995). Urese is the enzyme responsile of ure hyrolysis prouing mmonium (Guettes et l. 22). -N is one of the mjor nutrients for plnts, n uiquitous intermeite in plnt metolism (Von Wiren et l. 2). Beuse -N ssimiltion requires less energy thn tht of NO 3 -N, it is usully expete to e preferre y plnts (Britto et l. 21). However, the mmonium ion is notorious for its toxi effets on mny, if not ll, plnt strins: only few strins perform well when is the only, or preominnt, nitrogen soure (Kronzuker et l. 1997, Li et l. 29). In relity, mmonium is mrkely present in griulturl soils s result of fertilizers use, nitrogen yle, or pollution. This itionl -N input ffete speies omposition: even lol speies extintion, n lrge-sle forest eline ws ttriute iretly to the mmonium (Di et l. 28). Numerous stuies emonstrte tht ifferent N forms signifintly influene plnt growth, ut ontrsting results were oserve epening on the plnt speies use. Some plnts suh s mize, whet, too, en, preferre nitrte to mmonium nutrition (Wlh et l. 2, Guo et l. 22). These plnts woul suffer mmonium toxiity when supplie with high mmonium in the root meium s the sole N soure. Hving higher mmonium ssimiltion pity thn other plnt speies, those plnts oul voi mmonium toxiity n exhiite preferene for mmonium nutrition (Britto et l. 24, Guo et l. 27). Although the toxiity of mmonium regrless its origin, hs een oserve for more thn one hunre yers (Britto et l. 274

2 Plnt Soil Environ. Vol. 6, 214, No. 6: ), most reports onentrte on the stuy of niml (Alonso n Cmrgo 23, Aruzo 23), terium (Muller et l. 26), n higher plnts (Gerenás 1997, Britto n Kronzuker 22). In the present stuy, it ws suggeste tht mmonium iretly e in nutrient solution or iniretly proue y hyrolysis of ure ffete growth of plnts through photosynthesis inhiition. When mmonium ws e simultneously with nitrte, eleterious effets on growth were reue n photosynthesis tivity ws mintine. lulte following Vn Kooten n Snel (199). The intrinsi effiieny of open PS II (Ф ex ) (or effiieny of exittion energy pture y open PS II retion entres) ws lulte following Hrinson et l. (199). Sttistil nlysis. All vlues reporte re the mens of six replites per tretment (± SE), eh experiment eing onute in uplite. Dt were proesse y the vrine nlysis (ANOVA) n signifine levels were epte t P.5 t ll tests. MATERIAL AND METHODS Plnt mteril n growth onitions. Sees of tomto (Solnum lyopersion) were germinte in Petri ishes t 25 C in rkness. Uniform seelings were trnsferre to ontinully erte nutrient solution ontining low onentrtion of KNO 3 (.1 mmol). Ten ys lter, the seelings were supplie with nutrient solutions ontining KNO 3 (5 mmol), mixture of KNO 3 (3 mmol) n ( ) 2 SO 4 (2 mmol), ( ) 2 SO 4 (5 mmol) or ure (5 mmol). After 14 ys of tretment, 24-y-ol plnts were rey for the mesurement of ifferent prmeters onverte y this stuy. Determintion of hlorophyll ontent. Chlorophyll, n totl ontents were etermine s esrie y Arnon (1956). Mesurements of gs exhnge n hlorophyll fluoresene. Mesurements of net ssimiltion rte (A mx ), trnspirtion rte (E) n stomtl onutne (G W ) were me with CIRAS-1 gs exhnge system (PP Systems, Hithin, UK). Chlorophyll fluoresene emission from the upper surfe of the leves of intt plnts ws mesure y moulte fluorimeter (MINI-PAM) photosynthesis yiel nlyser (Wlz, Effeltrih, Germny). Leves previously selete for mesurement of stomtl onutne were use for fluoresene mesurements. The miniml (F ) n mximl hl fluoresene (F m ) emissions were ssesse in leves fter 3 min of rk pttion n the mximum quntum effiieny of PS II photohemistry ws lulte s F v = (F m F ). The prmeters were estimte following Bker n Rosenquist (24). Non-photohemil quenhming of fluoresene (NPQ), whih is proportionl to the rte onstnt of therml energy issiption ws lulte following Bjorkmn n Demmig (1987). The photohemil quenhing (q p ) ws RESULTS AND DISCUSSION Mny plnt speies show growth epression when mmonium ws supplie s sole nitrogen form Clussen n Lenz (1999). Pure mmonium nutrition hs negtive effet on ifferent growth prmeters suh s lef re, hlorophyll ontent n fresh mtter yiel (Figure 1) (Errehi n Wilox 199, R n Terry 1994). It ws suggeste tht the toxiity of -N ws orrelte with low ph vlue of growth meium resulting from the stoihiometry of exess H proution Rven (1986). Aiifition of the rhizosphere ue to ssimiltion of restrite tion uptke ompre with plnts reeiving mixture of nitrte n mmonium (Bsr n Goyl 22). In ft, presene of NO 3 -N plye lso n importnt role s osmotium esies its essentil funtion in ounter-ion for tion trnslotion in the xylem. Thus, there re reports initing tht -grown whet ontins lower C 2, Mg 2 n K onentrtions thn plnts supplie with NO 3 (Mrshner 1995). In our previous stuy, we emonstrte tht Ariopsis growth ws negtively ffete y mmonium when e t exess or efiient oses. In ontrst, the supply of verge quntity of mmonium enhne the growth of plnts (Nsroui et l. 213). Compre to seelings-fe with NO 3 -N s sole form of N, lower CO 2 ssimiltion rte, stomtl onutne n trnspirtion rte were foun for mmonium or ure-supplie tomto plnts. Moreover, the reution egree of these prmeters, ws llevite y ition of oth nitrte n mmonium (Figure 2). Suh results my inite tomto tolerne pity to low mmonium supply prllel with high proportion of NO 3 -N (Clussen n Lenz 1999). These results suggeste tht some of the verse effets of mmonium nutrition on plnt growth 275

3 Vol. 6, 214, No. 6: Plnt Soil Environ. () () Fresh weight (g) Lef re (m 2 ) NO3- NO3NH4 NH4 ure NO3-3 NO3NH4 3 NH4 4 ure Nitrogen soure () Chl mg/g FW Chl Tot Chl Chl NO3-3 NO3NH4 3 NH4 4 ure ure Nitrogen soure Figure 1. Chnges in fresh weight (), Chl, n totl ontents () n lef re () of tomto seelings grown in nitrogen solutions ontining either nitrte, mixture of nitrte n mmonium, mmonium or ure. Dt re mens ± onfiene limits (n = 6) were relte to photosynthesis. In ontrst to nitrte supply, the use of mmonium iretly furnishe or proue y hyrolysis of ure use reution of lef expnsion (Mrshner 1995), leing to higher riulose-1,5-isphosphte roxylse/oxygense (Ruiso) mount n tivity, hlorophyll ontent n ensity (Guo et l. 2, 27). To explin how nitrogen form influenes photosynthesis, photo-energy onsumption n reutnt supply were oserve. The ifferenes in photo-energy onsumption n reutnt supply etween nitrte n mmonium-grown plnts were isusse previously (Gerenás et l. 1997). It is generlly epte tht the isrepnies oserve were relte to the ifferent ssimiltory pthwys of nitrte (in shoots) n mmonium (in roots). Briefly, the totl ost in eh N form sorption, trnsport, reution, n ssimiltion vrie lrgely (Rven 1985). Compre to photosyntheti CO 2 ssimiltion, the N ssimiltion into glutmte is very importnt sink for reox equivlents from the photosyntheti eletron flow (Chmpigny n Foyer 1992). Generlly, mmonium is toxi to plnts n its toxi effet ws reue y ssimilting the mmonium into orgni ompouns in the roots vi the glutmine () () A mx (μmol CO 2 /m 2 /s) G w (mmol H 2 O/m 2 /s) Figure. 1 NO3-3 NO3NH4 3 NH4 4 ure Nitrogen soure () E (mmol H 2 O/m 2 /s) NO3-3 NO3NH4 3 NH4 4 ure Nitrogen soure Figure 2. Chnges in CO 2 ssimiltion rte (A mx ) (), trnspirtion (E) () n stomtl onutne (G W ) () in leves of tomto seelings grown in nitrogen solutions ontining either nitrte, mixture of nitrte n mmonium, mmonium or ure. Dt re mens ± onfiene limits (n = 6) 276

4 Plnt Soil Environ. Vol. 6, 214, No. 6: synthetse/glutmte synthetse (GS/GOGAT) (Nsroui et l. 21). The suppression of CO 2 ssimiltion rte oul e ue to the ompetition for ron skeletons n photogenerte reutnt etween the photosyntheti CO 2 fixtion n -N ssimiltion (Elrifi et l. 1988). It ws suggeste tht -N ssimiltion h muh higher requirement rtio for ATP/NADPH thn for CO 2 n NO 3 ssimiltion (Turpin n Brue 199). The thylkoi oun NAD(P)H epenent PQ reutse tivity-nad(p)h ehyrogense meite yli eletron trnsport roun PS I (Mi et l. 21). It seems tht the min ftor limiting net photosynthesis (expresse s A mx ) y -N ws stomtl losure, whih ourre when high mmonium onentrtion or ure nitrogen were e in ulture meium. The lrge iminution in G w suggeste tht stomtl losure ws one of the most importnt ftors ontriuting to epress photosyntheti ssimiltion rte. These results in tomto gree with those of Lwlor n Corni (22), who showe tht stomtl losure ws the min ftor in the reution in lef photosynthesis uring ioti stress. The other reson tht my e involve to explin why -N or ure shoul inue lower G W ws the poorer osmoti justment. Moreover, lower ontent of ifferent tions n espeilly K my ffet stomtl funtion (Lporte et l. 22). Alterntively, erlier root senesene use y -N my e the use of the lower G W in these plnts (Britto n Kronzuker 21, Bsr n Goyl 22). Delines in the ifferent gs exhnges ue to -N soure were ompnie y signifint ifferenes oserve for the hlorophyll fluoresene prmeters stuie in this work (F v, q p n NPQ). In these t, stuy of hlorophyll fluoresene prmeters inite tht the effiieny of the photohemistry of PS I1 ws ffete y mmonium stress. In ft, mmonium ws supplemente in nutrient solution lone ut t high ose, simultneously with nitrte or proue y hyrolysis ure yle. Inee, the F v rtio etermine on the fully expne leves ws inhiite in tomto plnts tht reeive -N lone or ure s nitrogen soure. Thus the hnges oserve in F v rtio vlues help us to explin the erese in photohemil quenhing oeffiient q p (Figures 3,). This eline in q p inite tht the primry eletron eptor of PS II, QA, ws less oxiize. This suggeste tht in stresse plnts the photohemil onversion n the pity of the eletron trnsport for the reution of NADP were ffete. On the other hn, the quntum yiel of photohemil effiieny of PS I1 ws ffete, thus initing tht mmonium interfere with the light retions of photosynthesis. The rise of non-photohemil quenhing oeffiient inite tht higher proportion of sore () F v () qp () NO3-3 NO3NH4 3 NH4 4 ure Nitrogen soure NPQ Figure. 2 NO 3 ure Nitrogen soure NO3-3 NO3NH4 NH4 ure Figure 3. Chnges in F v rtio (), photohemil quenhing (qp) () n non photohemil quenhing (NPQ) () in leves of tomto seelings grown in nitrogen solutions ontining either nitrte, mixture of nitrte n mmonium, monium or ure. Dt re mens ± onfiene limits (n = 6) 277

5 Vol. 6, 214, No. 6: Plnt Soil Environ. photons ws lost s het inste of eing use to rive photosynthesis) (Figure 3). We n onlue tht regrless mmonium origin (nitrogen soure or lierte y ifferent metoli yles s ure hyrolysis), high -N level present in plnt tissues ffete plnts growth. This negtive effet ws generte s onsequene of photosynthesis proess perturtion n epene minly on the ontent of photosyntheti pigments. Anomly of light energy issiption s fluoresene ws not only initive of lower hlorophyll ontent, ut lso photohemil energy onversion erese. The enhnement of photosynthesis proess n eline of hl fluoresene intensity together with pigment umultion in mixture fe- tomto, revele tht prtil sustitution of -N y NO 3 -N ws enefiil to the growth of this plnt. However, ition of high -N ose lone or ure n esily n signifintly mge growth plnts. REFERENCES Alonso A., Cmrgo J.A. (23): Short-term toxiity of mmoni, nitrite, n nitrte to the quti snil Potmopyrgus ntiporum (Hyroiie, Mollus). Bulletin of Environmentl Contmintion n Toxiology, 7: Aruzo M. (23): Hrmful effets of un-ionize mmoni on the zooplnkton ommunity in eep wste tretment pon. Wter Reserh, 37: Arnon D.J. (1956): Chlorophyll sorption spetrum n quntittive etermintion. Biohimi et Biophysi At, 2: Bker N.R., Rosenquist E. (24): Applitions of hlorophyll fluoresene n improve rop proution strtegies: An exmintion of future possiilities. Journl of Experimentl Botny, 55: Bsr A.S., Goyl S.S. (22): Mehnisms of improve nitrogenuse effiieny in erels. In: Kng M.S. (e.): Quntittive Genetis, Genomis n Plnt Breeing. CAB Interntionl, Louisin Stte University, Bton Rouge, Björkmn O., Demmig B. (1987): Photon yiel of O 2 evolution n hlorophyll fluoresene hrteristis t 77 K mong vsulr plnts of iverse origins. Plnt, 17: Britto D.T., Kronzuker H.J. (21): Constny of nitrogen turn:- over kinetis in the plnt ell: Insights into the integrtion of suellulr N fluxes. Plnt, 213: Britto D.T., Kronzuker H.J. (22): toxiity in higher plnts: A ritil review. Journl of Plnt Physiology, 159: Britto D.T., Siiqi M.Y., Glss A.D.M., Kronzuker H.J. (21): Futile trnsmemrne yling: A ellulr hypothesis to explin mmonium toxiity in plnts. Proeeings of the Ntionl Aemy of Sienes of the Unite Sttes of Ameri, 98: Britto D.T., Ruth T.J., Lpi S., Kronzuker H.J. (24): Cellulr n whole-plnt Chlorie ynmis in rley: insights inti hlorie-nitrogen intertions n slinity responses. Plnt, 218: Brynes B.H., Freney J.R. (1995): Reent evelopments in the use of urese inhiitors in the tropis. Fertilizer Reserh, 42: Chmpigny M.L., Foyer C. (1992): Nitrte tivtion of ytosoli protein kinses iverts photosyntheti ron from surose to mino i iosynthesis: Bsis for new onept. Plnt Physiology, 1: 712. Clussen W., Lenz F. (1999): Effet of mmonium or nitrte nutrition on net photosynthesis, growth, n tivity of the enzymes nitrte reutse n glutmine synthetse in lueerry, rsperry n strwerry. Plnt n Soil, 28: Di G., Delois C.P., Liu S., Juneu P., Qiu B. (28): Differentil sensitivity of five ynoteril strins to mmonium toxiity n its inhiitory mehnism on the photosynthesis of rie-fiel ynoterium GeXinMi (Nosto). Aquti Toxiology, 89: Elrifi I.R., Holmes J.J., Weger H.G., Myo W.P., Turpin D.H. (1988): RuBP limittion of photosyntheti ron fixtion uring NH 3 ssimiltion. Plnt Physiology, 87: Errehi M., Wilox G.E. (199): Tomto growth n nutrient uptke pttern s influene y nitrogen form rtio. Journl of Plnt Nutrition, 13: Gerenás J., Zhu Z., Benixen R., Rtliffe R.G., Sttelmher B. (1997): Physiologil n iohemil proesses relte to mmonium toxiity in higher plnts. Journl of Plnt Nutrition n Soil Siene, 16: Guettes R., Dott W., Esentreger A. (22): Determintion of urese tivity in soils y ron ioxie reles for eotoxiologil evlution of ontminte soils. Eotoxiology, 11: Guo S., Brük H., Sttelmher B. (22): Effets of supplie nitrogen form on growth n wter uptke of Frenh en (Phseolus vulgris L.) plnts. Plnt n Soil, 239: Guo S.W., Zhou Y., Go Y.X., Li Y., Shen Q.R. (27): New insights into the nitrogen form effet on photosynthesis n photorespirtion. Peosphere, 17: Hrinson J., Genty B., Bker N.R. (199): The reltionship etween CO 2 ssimiltion n eletron trnsport in leves. Photosynthesis Reserh, 25: Kronzuker H.J., Siiqi M.Y., Glss A.D.M. (1997): Conifer root isrimintion ginst soil nitrte n the eology of forest suession. Nture, 385: Lporte M.M., Shen B., Trzynski M.C. (22): Engineering for rought voine: Expression of mize NADP-mli enzyme in too results in ltere stomtl funtion. Journl of Experimentl Botny, 53: Lwlor D.W., Corni G. (22): Photosyntheti ron ssimiltion n ssoite metolism in reltion to wter efiits in higher plnts. Plnt, Cell n Environment, 25:

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