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  • growth Effect of nitro gen source on response to salinity stress wheat

    In maIze and

    By O. A. M. LEWIS*, E. O. LEJ DI AND S. H. LIPS

    P lant A daptatioll R esearch U llit , Th e Jacob Blausteill Institut e for D esert R esearch, Ben C llrion U lli'L'ersity 01 the Nege'L', S ede Boqer Campus, Israel 8-1993

    " l ' :\1 :\ 1 t\ H Y

    ' rh e e fleel 0 1' HmnlOnium 'lIld nitra te nutri t io n on mai zc and \\"h cat g ro\Vn hyd ro [)o ni eall) ' a nd sa linity st ressed II'

  • (am m o nium o r ni trate) and the p h otosyn th e ti c path way (C3 o r C4) w hi ch th e p lan t possesses. Th ese effects we re quant ifi ed b y th e m easurem en t o f g rowth rate, moisture eontent , root: sh oot rat io , photosynth et ie rate, transpirat ion rate, s tomata l

    co ndu c tan ce and t ran spirat ion rat io (wate r use cf-lie ien ey) in the expe rim ental plants.

    MATE !!I A L S ANO :vIET H O O S

    G rlJzu / h CO l1diÚOIIS

    Tri /iC/1111 aes /iVIIIII L. va r o Barkay an d Zea mays L . varo H aze ra were g ro wn to 31 and 2 1 d respect ive ly JI1 h yd ropon ic culture, after w h ich rh e p lanrs we re h a r"ested.

    T h e ma lze p lanrs were ra ised 111 rhe open dur ing Jul y and August unde r eondi t ion s s uitab le fOI' plants possessing th e C4 path way. M idda y irra cli ance was c. 2500 l' E m "s 1 , miclda y temperatures Au ctuated between 2X an d 35 oC and ni g ht temperaru res did not fa ll be low 20 oC, Da ytime rc lat ive humidiry

    va ri ed between 20 ancl 35 °o. Th e wheat p lants we re ra ised 111 a fib re-g lass-roofed g reenhouse during

    Scptembe r an d October unde r conditions more s u ita h le ror pl an rs possessi ng th e C3 phorosynth eti c pathway. Midday temperarures 111 t he g reenho usc Hu c ru a ted between 25 an d 30 oC w ith nighr rem- penltures berween 7 and 14 oC. Daytime relat ive humidities we re between 25 and 35 (jo bur ni ght- time

    humiditi es rose on occas ions to 85 "". M idda y irradia nce on the usuall )' c loud lcss days was measu red at between 700 and 750 l/ E m - t S- l.

    ¡;;xperilll ell/al de /ail

    1 n the maize ex periments, e ig h t p lants were g rown in each of sixtee n 20 l p lasr ic conta ine rs with ho les d rill ed in th e lids to accommodate them . 'rhe plants we re g rown to 21 days on we ll -aerared Long Ash ro n growth med ia modified to co n ta in nitrate-onl y o r am- m o nium -on ly as the 4 mM ni rrogen souree (1I e", irr, 1966); rh e pH of th e solu rion s was m

  • 12 m :\'1 C a treatme nts (2 co ntaine rs each) fo r salinit y s tressed nitl'a te -fed a nd ammonium-fed pl ants , Th e p la nts w e re h a rves ted afte r 3 1 d ays and trea ted as in the m a ize e xpe l' im ents , 1 n a ll th e a bo \'e ex pe riments NaCI was add ed to th e nutri e nt solu t io n s unl\' aftcr

    th e plants w e re 7 d ay s o ld an d th e n in 20111\1 p e r day i n c re m e nts ,

    G a s exclwlIge o llalysis

    Net ph o tllsynthe ti c rate (p,,) and tran spiration a l w ate r lo ss (7~, ) we re d e te rmin ed hy th e use of a P arkin son' s lea f c hmnbe r li nk ed 1'0 an AD C L C A

    infrare d g as an a lyse r (A nal yt ica l D eve lopme nt C or- p uration , Hodd esdon , Eng la nd) , Dcte rmination s

    \",e re m a d e on fiv e sep a rate plants b e long in g to each t r eatm e nt and th e results fo r each trea tm ent

    ave raged , F o r mai ze pl a nts, gas exchange d e te r - rnin a ti o n s \Ve re made an ho ur be fo re midda y al' an i rradi an ce 0 1' 250ü ¡t1-;: m ~ S- I, a tempe rature 0 1' 35 oC a nd an ambi e nt relati\'e humidity 0 1' 30 !l ", For \", h ea t pl ants , t h ese d e te rmin ati o ns we re m ad e at an irradi an ce 0 1' 700 I I E m-~ s 1, a tempe rature 0 1' 28 oC a nd a n ambi e nt re lat ive humidi ty 01' 35 "" , Stol11i1ta l conduc ta n ce (e,) to wa te r vap o ur was calculated f rom th ese fi g ures us ing Parkin so n 's fo rmulae (AD C LCA in s tru c ti on manual, 1986), and trans piration r a ti o (TR) was ca lcu la ted b y di\'iding T, by p", G as exchange d e terl11in ati o n s we re mad e on cl ear days 1 0 1' 2 days b efore th e date 01' h a lTes t ,

    RE SU LT S

    T h e resp ecti ve g ro \Vth res p o nse 01' nitra te- and a ml11 oniul11-fed mai ze p lants to salinit y stress can be

    o b se r ve d in th e datn rccO l'ded in Tab le 1, Fro m th ese data it is obv iou s th a t nitrate -fed p la nts a re fa r m o re

    salt-to le rant than th e ir ammonium-fed counte rpa rts und e r th e ex perimenta l conditions, vVh e reas nitra te -

    fe d plants sho w ed no redu ction in dry mass and only

    a s li ght reducti o ll in fres h l11 ass up 1' 0 th e 50111\1 sal inity leve l, th e effect 0 1' salini t ~ , o n th e fresh a nd dry m ass 01' ammonium-fed pl an ts e \'e n a t a cOll centration 01' 20 1ll ~ 1 was \'e ry m a rk ed nnd becam e in c reas ing ly so with in c reas ing sa lini ty, \V hil e a ll th e nitra te -fed p la nts w e re still g ro \\' ing

    \'i goro u s ly at th e ílO m\'1 sa lini ty le ve l, m any o f t he alllmoniull1-fcd p la nts \I'e re sho \l'ing s ig ns o f se\'e re wilt and sOlll e lI'e re actu a ll y d y in g , Th e contras t 01' th e salinity res po nse of th e pl:lI1ts fed rh e t\l 'O

    nitrog en sources is am p lified b~' th e fa e t th a t unde r non- salin e condition s th e allllll o niul11 - fed pl an ts

    w et'e pe rcep t ibly large r t h an th e nitrate- red plants , a fenture alread y n o te d b y lVI urph~' (1 984- ),

    An inspec tion 0 1' th e shoot: roo t ra tio s reeo rd ed in Table 1 sh o \Vs that in plants red b o th nitrogen sou rces th e sa 1 i n i t y e A'ee t on g rOll'th was m o re

    noti cea ble in th e s hoo ts rhan 111 th e roots , A

    relllarkablc feature of th e non -sa linity-stressed

    plants in (hi s ex pe rim cnt \I'as rha t ('he rres h \I 'e ig hr shoo t: roo t nlti os in the

  • o o ....

    o o

    .g E o o ....

    o o

    .

  • Table 4. Respollse of lIe / ph%sYII/ltetic ro/e, Irallspira/ioll ro/e, s/o/ll a/al cOlldllc/allce alld /rallspira/ioll ra/io (wa ter u/iliza /ioll efficiellcy) of w hea/ p/allls /0 differell/ cOllcen/ra/ioIlS alld eOlllbilla/iollS of C a alld NaC/

    Ca conc. (mM)

    NaCJ con c . (mM)

    Net photosynth ct ic rate

    Transpiration rate

    Stomata l conducta nce (to ¡--l.,O molecul es ) (mmo-I m 2 S- I)

    ' 1 'ranspi ration ratio

    (/,mo l m 's ') (mmo l m - ' S ') (m o l H,O j mol CO,)

    N itrate-fed plallts

    2 2 6

    ] 2

    ()

    60 60 60

    8'5 1 ± O'50 R32 ± 1 73 9·29 ± ()'9 2 8·75± 1· IO

    5'8 1 ±ü'46 5·-1-6± 1·11 6'97±O-1-9 7,25 ± O'61

    280 ± 29·3 2 17 ± 6,H 285 ± 16, 1 298 ± 35 ·6

    683 656 75 0 832

    Ammonium-fed plants

    2 2 6

    12

    o 60 60 60

    875 ± 1 26 7·9 1 ± 1· 2-1- 8'2X ± O'72 7'59 ± 0'53

    H9 ± ()'81 6,3 2 ± 1· 53 6·38±O·56 6·0-1- ± O·6-1-

    330 ± -1-8·R 226±73 1 268 ± 277 237±39'2

    856 799 770 796

    l\ 'leasurements "'ere made at a n irrad ian ce of 70() /' E m 's " a tempe raturc of 26- 28 oC and an amb ient re l ati\'t~ humidity of 35 "".

    g rown m a ize a nd \\'heat, ammonium-fed plants s h o\V

    a co n s ide rably g reate r se n s iti\ ' ity to sa linit~ , than do

    nitrate-fcd p lants , an eHect that is lik e ly to b e

    e nhan ced und e r fle ld conditions , The ca u se 01' t hi s e ffect is not imm ediate ly appa re nt but could possib ly

    be ascribed to o n e 01' the fol lowing factors, (a) 1n \Vheat and maize, nitrate ass imil atio n takes

    p lace primaril y in the shoot and amlllonium ass imi-

    lat ion in the roor. As the roots are in imlll ed iate contact \Vith the sa lin e containing nutri ent medium

    it is possib le that nitrogen assimi lat ion 111 am- rnonium-fed p lants is dis located by ionic eA'ects

    w hi ch \Vould not intcrfere with leaf-based nitrogcn ass imilation,

    (b) In nitra te-fed p la nts a mal ate- nitrate shuttl e is operative b e t\-veen s hoot a nd root (Ben-Zioni, Vaadia

    & Lips, 1970), The abse n ce of this shuttle in ammonium -fed plants co uld bring about ion trans-

    locato r y prob lems which are exace rbated bv the uptake of NaC! .

    (e) The ass imilation 01' th e bu lk 01' nutri e nt n itroge n III the roots of ammoniulll-fed plants

    necessitates the diversion of large quantities 01' carbon to thc root to pro\' ide th e carbon ske leton s 01' the products 01' nitrogen assimilation . It is possible that this carbon metabolism is inhibited b v the

    presen ce of high conccntrations 0 1' sodium and c h loridc ions in the mot,

    Th e results 01' this expe rim c nta tion a lso indicare that in maize and wh eat, inhibition of photosynthl:s is

    is not one of the manifestations of sa linity toxicity except as a secondary e/lect in already h eav'i ly

    damaged p lants . S uppress ion of nitrate uptake or

    assim ilation which ca n be partIy reli e \'ed by the

    presence of hi g h co n centration s of calc iulll does appear to be a contributory factor to sa linit y toxicity

    in wheat, Our co n c lus ion s a re that oSll1otic factors r esultin g in cu rtaillll ent of ce ll g rowth and eventua l

    leaf wilt \\,e t'e the prime cause of sa linity toxi c it\" in

    th e ex p e rim enta l plants, but further research on th e

    water statu s of sa li nity st t'essed \\'heat and Illaize

    plants u