Pea oo s a ec immobilisa ion and solubilisa ion o phospho us
depending on geno ype, s age and phospho ous sou ce
HANNU AHOKAS , EILA HEIKKIL Ä and LEENA RAMSTEDT
MTT – Ag i ood Resea ch Finland, BEL, ET-house, Jokioinen, Finland
Ahokas, H., Heikkil ä , E. and Rams ed , L. 2011 . Pea oo s a ec immobilisa ion and solubilisa ion o phospho us depending on
geno ype, s age and phospho ous sou ce. – He edi as 000 : 1–8. Lund, Sweden. eISSN 1601-5223. Recei ed 16 Feb ua y 2010.
Accep ed 5 May 2011.
To assess he e i ciency o pea oo s o mobilize a ailable phospho us (P) om P compounds we subjec ed a ious pea geno ypes o
a pos - ea men me hod. Axenic seedlings we e aised on P-de i cien semisolid syn he ic medium using con ol blanks wi hou a
plan o he wise ea ed in he same way. AlPO
4 , CaHPO 4 , FePO 4 , apa i e and mea -bone-meal (MBM) we e es ed. A geno ype was
es ed om 1-day h ough 15-days o g ow h. The e we e di e ences be ween he compounds (p ⬍ 0.001). P was dissol ed om
CaHPO
4 wi h appa en maxima a 72-h in e als and o a signi i can ly lesse ex en om MBM. Wi h AlPO
4 , FePO 4 and apa i e, he
oo s did no show a dissol ing e ec , bu , on he con a y, signi i can ly immobilised P.
In each case a co ela ion wi h an inc ease in acidi y, H
⫹ (p ⬍ 0.001) was obse ed. The co ela ion was nega i e in he
AlPO
4 , FePO 4 and apa i e se ies. A CaHPO
4 ea men combined wi h apa i e o MBM signi i can ly dec eased solubili y o
P om ha o CaHPO
4 singly. Tes s wi h six addi ional geno ypes showed ha all solubilised P om CaHPO
4 , some o a signi i -
can ex en om apa i e, MBM o sligh ly om FePO
4 , bu none om AlPO
4 . The accumula ion o nea ly wa e -insoluble alu-
minium and i on phospha es in i eld and i gin soils is pa ly explainable by he immobilisa ion h ough he oo ac ion on P,
which we ha e ound also wi h o he plan species. The oo esponses mus also ha e ecophysiological unc ions dis inc om P
acquisi ion.
Hannu Ahokas, MTT – Ag i ood Resea ch Finland, BEL, ET-house, FI – 31600 Jokioinen, Finland . Email: [email p o ec ed]
The esou ces o e ilize phospha es a e declining
globally ( VANCE e al. 2003). I is, he e o e, impe a i e
o unde s and he P (phospho us) acquisi ion o c ops. O
all he nu ien elemen s, soil P is he mos immobile,
inaccessible and una ailable one ( HOLFORD 1997).
Wha li le na i e P he e is in ge mina ing pea ( Pisum
sa i um ) g ains is a mino and sho ly exhaus ed sou ce.
The mean P con en o d y pea g ains was ound o be
only 0.37 o 0.38% ( SCHERZ and KLOOS 1981; RASTAS
e al. 1989). The main P ese oi s in he pea g ains a e
nucleic acids and inosi ol phospha es. All o he g ain P
is p obably no in he o m suscep ible o be mobilized a
ge mina ion. Abou 80% o he inosi ol phospha es, he
appa en s o age P in pea, we e deg aded in 8 days a e
ge mina ion ( HONKE e al. 1998). Ac i e means o P
acquisi ion a e supposed o begin al eady in ge mina ion
in associa ion wi h ela i ely young sec ions o oo s.
We ( AHOKAS and MANNINEN 2001) ha e ound ha such
ac i i ies s a on he 4 h day o ge mina ion in ba ley
( Ho deum ulga e ).
Case s udies in Finland ( SAARELA e al. 2003, 2004)
show ha insoluble phospha es de i ed om e ilize s
seem o ha e accumula ed in soils. Fe ilize s con ain
phospha e in he o m o CaHPO
4 . Aluminium phospha e
o i on phospha e, o bo h, a e known o accumula e in
Finland in pea soils ( VALMARI 1970; NIEMINEN and
J ARVA 1996), i gin mine al soils ( KAILA 1963) and i eld
soils ( KAILA 1963, 1964; HARTIKAINEN 1989; SAARELA
e al. 2003) c ea ing a soil sedimen o P. The mobilisa-
ion o his esou ce is o in e es he e. I seems ha he
accumula ed sedimen s o P in he i eld soil a e no used
in plan p oduc ion. In he oo s o ba ley, aluminium is
abso bed by cell walls and oo su aces and p ecipi a e
phospha e he e ( CLARKSON 1967), a p ocess which may
con ibu e o he insoluble phospha e in pos -ha es soils
g own wi h ba ley.
This s udy is an ex ension o he p e ious one on ba ley
( AHOKAS e al. 2007). The aim o he s udy was o assess
gene ic a ia ion using di e en pu a i e phospho us
sou ces wi h pea.
Because P a ailabili y in he o m o annually added
e ilize ee om pollu ing elemen s is becoming mo e
expensi e, i may be p uden o s a b eeding c ops wi h
p ope ies which u ilize he soil-bound esou ces o P o
bone meal, a ecyclable P sou ce. The mea bone meal
p oduc s udied he e was accep ed by EU o be used as a
e ilize . I was hough o ha e abou 40% o i s P a ail-
able o c ops ( KALLAMA and UUSIHONKO 2006). The apa i e
ype s udied he e has been ied as a P sou ce in o ganic
cul u e ( SEURI e al. 2001).
He edi as 148: 85–92 (2011)
© 2011 The Au ho s. This is an Open Access a icle. DOI: 10.1111/j.1601-5223.2011.02177.x
86 H. Ahokas e al. He edi as 148 (2011)
MATERIAL AND METHODS
Plan s and g owing medium
B eeding lines and old cul i a s o he pea we e selec ed
wi hou p e ious in o ma ion o hei P up ake p ope ies.
The pea line L1703 was ob ained om D . S ig Blix ,
Weibullshom Plan B eeding Ins i u e, Sweden. I is a
selec ion o c . ‘ Vinco ’ ( MURFET 1967). The o igin o he
line V84 – 77 was desc ibed p e iously ( AHOKAS 1987);
i is in p inciple he geno ype o L200 in BLIXT ’ s (1972)
collec ion. The line 93 – 893 is o hyb id o igin ( Pisum
ela ius ⫻ Ville) ⫻ (V84 – 77 ⫻ Ville) and o F
8 o la e
gene a ion c ossed and b ed by one o us (H. Ahokas).
The old Finnish pea en ies, Linie on No d (K – 2402),
he land ace lines, Linie on Lande bse (K – 2406), and
Sou h-Wes Finnish (K – 3668) and c . ‘ Kelle ä ’ (K – 2403)
we e ob ained om he N. I. Va ilo All-Russian Scien-
i i c Resea ch Ins i u e o Plan Gene ic Resou ces,
S . Pe e sbu g, Russia. The seeds we e p oduced in g een-
house. To educe possible gene ic a ia ion wi hin he
accessions, single plan o igins we e used. The seeds we e
usually picked om ma u e pods s o ed unopened wi h
s e ile o ceps, pencil-ma ked, weighed and su ace
s e ilized and washed in s e ile wa e se ies as desc ibed
( AHOKAS and MANNINEN 2001; AHOKAS e al. 2007), how-
e e , using he acuum ea men only in he Linie on
No d se ies, because he ge mina ion in some o he pea
lines appea ed o be impai ed by he acuum s ep du ing
he s e ilisa ion in 0.01% HgCl
2 . The plan s, single pe
a 14-ml polyp opylene ube (Falcon 2059, USA), we e
g own o 1 o 15 days on abou 7 ml o medium made
semisolid wi h 0.6% aga o abou 42 mg pe ube (Plan
Cell Cul u e Reagen s, A – 1296, Sigma, USA) ha ing he
ino ganic cons i uen s o Ba ley Medium II ( NORSTOG
1973) bu lacking phospha e he plan s being subjec ed
o P s a a ion bu supplied wi h o he mac o and mic o
mine als o Ba ley Medium II. The sal s we e o analy i-
cal (Me ck, Ge many) o Plan Cell Cul u e Reagen s
g ade (Sigma, USA). The masses o bo h he emp y ube
be o e he expe imen and he medium we e eco ded. In
calcula ions, 1 g o he medium was aken as 1 ml. A leas
wo con ol ubes wi hou any plan we e included o
each sample se ies o he di e en P compounds o de e -
mine he ze o le el. The daily se ies comp ised o 12 o
24 ubes. The na u al pH (in mean 5.74) o each con ol
medium (wi hou a plan ) a he sampling day was used as
he e e ence o he calcula ions o he acidi i ca ion
by he plan . Fo he pH measu emen s wi h pH-Me e
CG840 (Scho , Ge many), he plan less blank medium
was mixed wi h a s e ile glass od and he elec ode
(Scho N 6180) was inse ed midway in he medium in
he ube. The pH measu ing appa a us was calib a ed
be o e each se ies o measu emen s. The elec ode solu-
ion was changed once a mon h. The pH was exp essed as
mic o-equi alen l
– 1 o H
⫹ . The expe imen s we e done
in an ai -condi ioned g eenhouse be ween la e au umn
and ea ly summe wi h nigh minima o 9 – 13 ° C and day
maxima o 20 – 25 ° C a he plan le el. Addi ional ligh
was supplied wi h high-p essu e sodium lamps (Philips
SON – T AGRO 400, Belgium) o gua an ee a 16-h day-
leng h, being u ned on and o by a pho osenso ou side
he g eenhouse du ing he illumina ion pe iod. A di e -
en pe iods o he yea , he se ies we e subjec ed o he
no he n la i ude o abou 61 ° wi h a ying na u al ligh
in ensi ies and spec al dis ibu ions.
Tes ing he phospho ous compounds
CaHPO 4 ( ⫽ CaP) (BDH 27598, UK), FePO
4 ( ⫽ FeP)
(Me ck 103923, Ge many), AlPO
4 ( ⫽ AlP) (Ald ich
34,145 – 2, Ge many) and Siilinj ä i Apa i e (Kemi a
G owHow, Finland) we e g ound in a mo a , washed a
leas i e imes du ing a day wi h s e ile Milli-Q wa e
using 10 olumes o mo e, collec ed by cen i uga ion and
d ied a 62 – 65 C o h ee days on Wha man 1 (UK) i l e
pape and s o ed exsicca ed. The g ound mea bone meal
( ⫽ MBM) (Honkajoki Oy, Finland) was used as such. The
MBM has been subjec ed o au ocla ing a 133 C o
20 min in he p ocess o he ac o y and was s o ed a
– 20 ° C du ing he expe imen . The P con en o MBM is
indica ed o be 5.5 %. Siilinj ä i Apa i e ep esen s l uo-
oapa i e ( NEUVONEN 1960) wi h a epo ed o al P con en
o 14% and wi h wa e soluble P o 0% and wi h o iginal
pa icle size ac ions o ⬍ 0.06 mm 40%, ⬍ 0.1 mm 60 %
and ⬍ 0.3 mm 95 % ( ANONYMOUS 2003). Each compound
con aining phospho us was weighed (10 mg) on pa ly cu
1-ml pipe o ips in ad ance used o inse he compound
on he medium in he g ow h ube.
A e he plan s we e pulled ou , he semisolid medium
mixed and he pH measu ed, he abili y o he medium in
each ube o dissol e phospho us om CaP, FeP, AlP,
apa i e o MBM was de e mined. Two pe sons wo ked
oge he wi hou any delays un il he i nal sample was
ob ained o he P de e mina ion. A ube wi h he medium
was mixed wi h he 10 mg compound wi h a glass od o
30 s, he ubes we e capped, s uck by hand o lowe he
medium in he ube and incuba ed in a 25 ° C wa e ba h o
1 h. A e 15 s igo ous o exing, he ubes we e cen i-
uged a abou 9500 g in an angle o o (Beckman JA – 20.1,
USA) o 10 min a ⫹ 8 ° C se ing. The supe na an was
collec ed wi h wide-po e 1-ml ips (Geno-DNA- ip,
Finnpipe e, Finland) on a pipe o in wo chilled 1.5-ml
Eppendo (Ge many) ubes. The ubes we e cen i uged
a abou 15 000 g in a So all FA-MICRO o o (USA)
o 5 min a 8 ° C se ing, and he supe na an s pooled usu-
ally o make ⬎ 1.5 ml by pou ing o a p e-chilled 2-ml
ube. The samples we e s o ed in ice and de e mined wi hin
a ew hou s o ozen ( – 20 ° C) o de e mina ion la e . In a
He edi as 148 (2011) Pea geno ypes, oo s and phospho us solubilisa ion 87
ep esen a i e o he oldes pea cul i a (No d) eleased in
Finland in 1904 ( AHOKAS 2000). Linie on No d was selec ed
om i in abou 1910 when e y li le a i i cial e ilize s
we e used. Linie on No d also ge mina ed uni o mly unde
he expe imen al condi ions. The mean pH le el o he con-
ol medium was ound o be 5.74, bu he oo -induced
acidi i ca ion exp essed as he inc ease o equi alen s o
H
⫹ ml – 1 was s onges a oo b anching in be ween 8- and
10-days samples declining la e unde he es condi ions
(Fig. 1). The acidi i ca ion and p ima y oo elonga ion
showed a hy hm o 72 h du ing he 9-days pe iod (Fig. 1),
a e which also he seconda y oo s s a o play a ole.
S a is ically, he i e es ed compounds showed highly
signi i can di e ences o e he 15-days pe iods: χ 2 ⫽ 305.9,
p ⬍ 0.001. A e a 6-days pe iod all he es ed compounds
seem o di e se om he p e ious solubilisa ion alues.
CaP, howe e , showed an ea lie esponse, wi h i s i s
peak in 3-days, he second in 6-days and he hi d in 9-days
samples. A e ha , he ac i i ies o he seconda y oo s
may ha e become o e whelming and he condi ions o
de elopmen may also be s ess ul.
CaP and MBM showed highly signi i can (p ⬍ 0.001)
posi i e co ela ion be ween acidi ying o he medium
and abili y o solubilise phospho us, while AlP, apa i e
and FeP showed highly signi i can (p ⬍ 0.001) nega i e
co ela ion (Table 1).
Phospho ous compounds in combina ion wi h CaP
Fo u he s udies, he 8-days sample age was selec ed o
ep esen a s age no much ye a ec ed by he seconda y
oo s o by he pu a i e s esses caused by he minu e
space o he plan . The e ec o he indi idual phospho-
ous compound oge he wi h a 10 mg aliquo o CaP and
singly was es ed in a se ies a he 8-day samples. The
esul s a e gi en in Table 2. FeP, AlP and CaP, 10 mg
each wi h an addi ional 10 mg o CaP did no change he
amoun o P solubilised om ha o he single 10 mg dose
o CaP, while apa i e signi i can ly a p ⬍ 0.01 and MBM
a p ⬍ 0.05 lowe ed he amoun o P solubilised compa ed
wi h he single (10 mg) samples o CaP.
Geno ypic e ec s
The esul s wi h six pea geno ypes a hei e i ciency o
make P soluble om he i e es ed compounds we e
de e mined wi h 8-days seedlings bo h on single plan
basis and co ec ed o he di e ences in single-seed
masses (Table 3, 4). The esul s o he unco ec ed and
co ec ed alues we e, howe e , cohe en . Wi h AlP all
he geno ypes consis en ly p ecipi a ed P compa ed wi h
he con ols wi hou a plan , e en hough L1703, 93 – 893
and Kelle ä p ecipi a ed somewha less. Signi i can di -
e ences we e ound, in pa icula , i co ec ed o he seed
mass. This mos ly mo es L1703 wi h i s la ge seeds
joined es , bo h 10 mg aliquo s o AlP, apa i e, CaP, FeP
o MBM we e mixed oge he wi h 10 mg o CaP simul a-
neously and he sample p ocessed o he wise as hose wi h
indi idual phospho ous compounds.
Phospha e de e mina ion
Phospha e was de e mined in 1.5-ml samples o he supe -
na an in 14-ml Falcon 2059 ubes in he me hod o DICK
and TABATABAI (1977) in a i nal olume o 10 ml. Bo h he
samples and con ol blanks wi hou plan s we e ead wi h
a spec opho ome e (HP 8452A, Ge many) a 700 nm
agains wa e . The eadings we e co ec ed o olumes o
he o iginal samples. In case ha less han 1.5 ml o he
supe na an was eco e ed, he olume was co ec ed by
calcula ion. Fo a s anda d plo o phospha e, dilu e
K
2 HPO 4 solu ion was added o he ube wi h he same aga
medium, Ba ley Medium II (see abo e), mixed o 30 s
wi h a glass od, incuba ed in a 25 ° C wa e ba h o 1 h,
cen i uged as he samples, and hen de e mined and
calcula ed on he mass basis as wi h he sample ubes.
S a is ics
The obse ed alues we e calcula ed on medium bases
wi hou seed mass co ec ion o co ec ed o a s anda d
g ain mass o 200 mg, which was app oxima ely he
mean single pea mass in Linie on No d. To ci cum en
any e o s caused by nonno mali y, he nonpa ame ic
s a is ics o p obabili y (p), K uskal-Wallis one-way ana-
lysis o a iance (H), Spea man ank co ela ion (
s ) and
F iedman wo-way analysis o a iance ( χ 2 ) we e used
and he signi i cances de e mined acco ding o SIEGEL
(1956). SEM means he s anda d e o o he mean, and n,
he numbe o samples.
RESULTS
The alues shown a e di e ences be ween he samples and
he con ol blanks ob ained wi h media wi hou a plan
(Ba ley Medium II). The alues can a y om posi i e
(solubilising) o nega i e (immobilising). In many cases
his makes he s anda d e o o he mean (SEM) alues
nume ically appa en ly high wi h ega d o he nume al o
he means. The alues a e p esen ed on he μ mol phospha e
pe ml o he medium o en bo h wi hou and wi h a co ec-
ion o he seed mass. Wi hin a geno ype such co ec ion
o seed mass has a ma ginal e ec , bu be ween geno ypes
he co ec ion is meaning ul especially because L1703 has
nea ly double he single-seed mass o he o he s.
Time se ies om 1-day ge minan s o 15-days seedlings
The esponses o seedlings in he ime se ies we e s udied
wi h he pea line Linie on No d. The line was chosen as a
88 H. Ahokas e al. He edi as 148 (2011)
Wi h FeP, L1703 and 93 – 893 showed posi i e alues, he
o he geno ypes p ecipi a ing P and wi h signi i can di -
e ences (0.02 ⬎ p ⬎ 0.01). The geno ypes L1703 and
93 – 893 also showed posi i e alues wi h MBM, he o he
geno ypes being nega i e hough nea ly ze o, gi ing no
s a is ical signi i cances.
owa ds he ze o alue. Highly signi i can di e ences
(p ⬍ 0.001) we e obse ed wi h apa i e as he sou ce,
whe e L1703 and V84 – 77 showed solubilising p ope ies,
he o he geno ypes showing consis en ly p ecipi a ion o
P. F om CaP all he geno ypes could make soluble P, he e
being no signi i can di e ences be ween he geno ypes.
Phospha e solubilisa ion
x 24 h
–PO4
3– mmol ml–1
–4
–2
0
2
4
6
8
10
MBM
Apa i e
FeP
AlP
CaP
Mean p ima y oo elonga ion
x 24 h
cm
0
2
4
6
8
10
12
Mean acidi y depa u e ( he con ol medium, pH 5.7 = 0)
x 24 h
0246810121416
0246810121416
0 2 4 6 8 10 12 14 16
mEq l–1
–16
–14
–12
–10
–8
–6
–4
–2
0
2
Figu e 1. Resul s on soluble phospha e quan i ies om di e en phospho ous subs ances in axenic media g own o 1 o 15 days
in i o wi h pea, Linie on No d. Values we e co ec ed o he ue g ain weigh o co espond esul s wi h a 200 mg g ain. – Top
plo : phospha e solubilisa ion o immobilisa ion (nega i e alues) ela i e o con ol blanks wi hou a plan sampled o each MBM,
apa i e, FeP, AlP and CaP. – Cen al plo : he elonga ion o he p ima y oo (mean ⫾ SEM) o all samples. – Bo om plo : acidi i ca ion
in mic o-equi alen s pe li e o he media ela i e o con ol blanks wi hou a plan (mean ⫾ SEM) o all samples. The change om
0 o –10 means an acidi i ca ion o one pH uni om pH 5.7.
He edi as 148 (2011) Pea geno ypes, oo s and phospho us solubilisa ion 89
mimics he clus e - oo ini ia ion de ec ed in many species
unde low P in he soil.
Doubling he amoun o CaP om 10 o 20 mg did no
a ec he amoun o phospha e solubilised (Table 2) sug-
ges ing ha he solubili y is dependen on he quan i y o
one o mo e speci i c subs ances sec e ed om he oo s
and ha he amoun o he es ed P subs ances was no a e
limi ing. The inabili y o some plan species o use P om
calcium phospha e was shown o ende hem calci uge
( TYLER 1994; ZOHLEN and TYLER 2004). The bes a ailabil-
i y o P om CaP ound in his s udy sugges s ha pea is
a he a calcicole han calci uge. The e we e signi i can
lowe ing in e e ences by apa i e and MBM wi h he
a ailabili y o phospha e om CaP in he joined expe i-
men s (Table 2). I such a phenomenon would occu in he
soil en i onmen oo, mixing o di e en ypes o P e i-
lize s, a leas CaP wi h apa i e migh be was e ul o P in
he pea oo en i onmen . In he case o apa i e as e i-
lize , including Siilinj ä i Apa i e, he i eld ials wi h
annual ba ley in o ganic a ming ( SEURI e al. 2001)
co obo a e he i nding ha P o apa i e is una ailable o
poo a ailable o ba ley. This was con i med wi h 7 o he
ba ley geno ypes wi h an in i o me hod ( AHOKAS e al .
2007). In soil, he es ed compounds would be subjec ed
o biological leaching. Then i is, howe e , mo e likely
ha he o ganisms making P a ailable p e e en ially ake
up he soluble P by hei own cells a he han supply i o
o he species.
Solubilisa ion o P om FeP, AlP and apa i e by pea
showed a nega i e co ela ion wi h he acidi i ca ion o
he medium (Table 1). SUBBARAO e al. (1997) ound ha
he pH o he oo exuda es o pigeon pea ( Cajanus cajan )
did no o co ela e wi h he P solubilisa ion, bu hey
asc ibed he p ope y o he chela ing compound eleased
by oo s. E iden ly he sec e ion o o ganic acids ha is
a ibu ed o pa icipa e in he mobilisa ion o P in he
hizosphe e ha e, o mainly ha e o he unc ions o he
DISCUSSION
The me hod o P de e mina ion used is insensi i e o
o ganic phospha es ( DICK and TABATABAI 1977). I is
he e o e sui able o accu a ely de e mina e any ino -
ganic P ha has p e iously been in con ac wi h he seed-
ling o he es plan and allows also using he o ganic
MBM as a es sou ce o P. The li le amoun , abou
42 mg pe sample o aga o plan cell cul u e pu i y
also appea ed in he con ol blank ubes and he ubes
o he phospha e s anda d and i s possible e ec s a e,
he e o e, ully con olled.
I is appa en ha only he ela i ely new oo s a e
e ec i e a dissol ing phospha e con aining compounds
in he soil. Unde he p esen es condi ions he abili y
pe sis ed up o 11 o 12 days, a e which new b anches
appea and la gely ake o e he ac i i ies o he p ima y
oo in pea. Linie on No d s udied o 1 day h ough
15 days, showed a 3-day (72-h) pe iodici y a solubilising
phospha e om CaP somewha associa ed wi h he p i-
ma y oo elonga ion a e and sec e ion o acidi y in o he
oo en i onmen . This las ed a leas o 3 ⫻ 3 days on he
p ima y oo s. The pe iodic appea ance o he solubili-
sa ion capabili ies a abou 72 h in e als owa ds CaP
Table 1. Coe i cien s o Spea man ank co ela ions
be ween soluble phospha e and acidi i ca ion wi h he
Linie on No d pea om 1 day h ough 15 days wi hou
co ec ion o seed weigh di e ences (c . Fig. 1).
Subs ance
Spea man ank
co ela ion,
s
Signi i cance,
p (d ⫽ 13)
AlP – 0.767 ⬍ 0.001
Apa i e – 0.889 ⬍ 0.001
CaP 0.932 ⬍ 0.001
FeP – 0.925 ⬍ 0.001
MBM 0.818 ⬍ 0.001
Table 2. In e e ence o phospho ous compounds wi h he solubilisa ion o P om CaP in media a e eigh days g ow h
o he Linie on No d pea.
Phospha e solubilised μ mol ml – 1
(Mean ⫾ SEM)
Phospha e solubilisa ion om
CaP-joined compound s
10 mg CaP singly
Compound, 10 mg each es ed
singly o joined wi h 10 mg CaP
Compound
singly n ⫽ 7
Compound joined wi h
addi ional 10 mg CaP n ⫽ 7 H Signi i cance, p
AlP – 1.19 ⫾ 0.16 1.93 ⫾ 0.32 0.494 ⬎ 0.30
Apa i e – 1.07 ⫾ 0.10 0.51 ⫾ 0.11 8.265 ⬍ 0.01
CaP 2.13 ⫾ 0.30 2.08 ⫾ 0.44 0.510 ⬎ 0.30
FeP – 0.80 ⫾ 0.28 1.72 ⫾ 0.53 0.690 ⬎ 0.30
MBM – 0.50 ⫾ 0.34 1.74 ⫾ 0.55 4.592 ⬍ 0.05
H 20.038 15.395
Signi i cance, p ⬍ 0.001 p ⬍ 0.01

90 H. Ahokas e al. He edi as 148 (2011)
He e he unde lying cause was ela ed o exuded pen-
anedioic acid ( SHEN e al. 2001). In a po expe imen
using neu al soils, syn he ic i on phospha e was ound o
se e as P sou ce o ye-g ass ( Lolium pe enne ) ( JOHNSTON
and RICHARDS 2003). B oad bean ( Vicia aba ) g own in
non-s e ile soil was hough o be capable o use P om
i on and aluminium phospha e, e en hough calcium
phospha e was he mos a ou able ( LI e al. 2007).
The obse a ion ha pea lines L1703 and 93-893 made
P soluble om FeP, while he o he ones p ecipi a ed P
(Table 2, 3, 4) in he sligh ly acidic pH sugges s ha
geno ypic di e ences exis in pea in his cha ac e is ic. In
li e a u e, FePO
4 is, in a ca eless way, lis ed among he
P sou ces a ailable o plan s in soil. Howe e , close
s udies ha e shown ha FePO
4 is eally an una ailable
P-sou ce o many plan s, including he Poaceae species
maize, so ghum and pea l mille ( AE e al. 1990, 1993;
A E and SHEN 2002). Geno ypic a ia ion o P up ake
om i on phospha e was ound in pigeon pea ( SUBBARAO
e al. 1997) and g oundnu ( WISSUWA and AE 1999).
A posi i e co ela ion was ound be ween P solubilising
o i on phospha e and o aluminium phospha e in pigeon
pea in es s, whe e mic obial pa icipa ion was in e e ed
plan and he in e ac ion o plan and oo en i onmen .
Mala e was ound o be he majo ca boxyla e ound o
be exuded om pea in soil ( NURUZZAMAN e al. 2005).
Al-induced ci a e sec e ion by ap and basal oo s o
bean ( Phaseolus ulga is ) showed geno ypic di e ences
( SHEN e al. 2004). The sec e ed compounds o he Linie
on No d pea unde P-de i ciency p obably ha e Al- and
Fe-de oxi i ca ion as one o hei unc ions o he adap a-
ion o he soil en i onmen .
Ou pos - ea men me hod uses axenic condi ions
de oid o in e ac ions wi h o ganisms in he hizosphe e,
which a e known o in e e e in P acquisi ion o plan s in
soil ( RENGEL and MARSCHNER 2005). SUBBARAO e al.
(1997) an es s las ing o weeks wi h he pe ennial
pigeon pea on non-s e ile soil. They also ound nega i e
P solubilisa ion om i on phospha e a some s ages. Phos-
pha es may be made a ailable o plan s wi h he aid o a
myco hiza ( BUCHER 2007). Unde i on de i ciency, al al a
( Medicago sa i a ) oo exuda es con ain a u an de i a-
i e capable o dissol ing e ic phospha e ( NOGUCHI
e al. 1994). Elephan g ass ( Pennise um sp.) was ound o
bene i om i on and aluminium phospha e in acid soil in
a ashion no explainable wi h hizosphe e acidi i ca ion.
Table 3. Ac ions o he oo en i onmen o six pea geno ypes on i e phospho ous compounds ela i e o he con ols
wi hou co ec ion o he seed weigh di e ences .
Phospha e, μ mol ml – 1 Mean ⫾ SEM [n]
Pea AlP Apa i e CaP FeP MBM
Kelle ä – 0.48 ⫾ 0.23 [7] – 0.59 ⫾ 0.42 [7] 1.90 ⫾ 0.33 [7] – 0.90 ⫾ 0.31 [7] – 0.16 ⫾ 0.37 [8]
L1703 – 0.37 ⫾ 0.17 [5] 2.11 ⫾ 1.24 [7] 2.74 ⫾ 0.59 [9] 0.78 ⫾ 0.71 [8] 0.73 ⫾ 0.50 [8]
Linie on Lande bse – 1.14 ⫾ 0.19 [6] – 1.08 ⫾ 0.05 [7] 2.20 ⫾ 0.18 [8] – 1.06 ⫾ 0.15 [7] – 0.32 ⫾ 0.13 [7]
Sou h – Wes Finnish – 1.34 ⫾ 0.21 [6] – 0.98 ⫾ 0.15 [7] 2.30 ⫾ 0.39 [8] – 1.13 ⫾ 0.22 [7] – 0.25 ⫾ 0.25 [7]
V84 – 77 – 1.08 ⫾ 0.21 [7] 0.15 ⫾ 0.51 [7] 1.50 ⫾ 0.29 [7] – 1.11 ⫾ 0.08 [7] – 0.22 ⫾ 0.32 [7]
93 – 893 – 0.30 ⫾ 0.54 [7] – 0.75 ⫾ 0.33 [6] 2.40 ⫾ 0.48 [7] 0.50 ⫾ 0.59 [9] 0.60 ⫾ 0.64 [8]
H 9.697 21.758 5.087 14.874 5.870
Signi i cance 0.10 ⬎ p ⬎ 0.05 p ⬍ 0.001 ns 0.02 ⬎ p ⬎ 0.01 ns
Table 4. Ac ions o he oo en i onmen o six pea geno ypes on i e phospho ous compounds ela i e o he con ols
wi h seed weigh s s anda dized o 200 mg om he esul s in Table 3 .
Phospha e, μ mol ml – 1 Mean ⫾ SEM [n]
Pea AlP Apa i e CaP FeP MBM
Kelle ä – 0.37 ⫾ 0.18 [7] – 0.60 ⫾ 0.35 [7] 1.52 ⫾ 0.22 [7] – 0.87 ⫾ 0.28 [7] – 0.21 ⫾ 0.31 [8]
L1703 – 0.17 ⫾ 0.08 [5] 1.00 ⫾ 0.58 [7] 1.39 ⫾ 0.32 [9] 0.38 ⫾ 0.37 [8] 0.39 ⫾ 0.28 [8]
Linie on Lande bse – 1.12 ⫾ 0.20 [6] – 1.02 ⫾ 0.06 [7] 2.07 ⫾ 0.17 [8] – 0.97 ⫾ 0.15 [7] – 0.31 ⫾ 0.12 [7]
Sou h – Wes Finnish – 1.14 ⫾ 0.17 [6] – 0.86 ⫾ 0.14 [7] 1.89 ⫾ 0.31 [8] – 0.93 ⫾ 0.18 [7] – 0.21 ⫾ 0.20 [7]
V84 – 77 – 1.02 ⫾ 0.22 [7] 0.13 ⫾ 0.43 [7] 1.25 ⫾ 0.23 [7] – 1.14 ⫾ 0.16 [7] – 0.20 ⫾ 0.28 [7]
93 – 893 – 0.30 ⫾ 0.45 [7] – 0.68 ⫾ 0.31 [6] 1.86 ⫾ 0.36 [7] 0.44 ⫾ 0.53 [9] 0.55 ⫾ 0.70 [8]
H 13.484 1.312 7.586 19.838 5.372
Signi i cance 0.02 ⬎ p ⬎ 0.01 p ⬍ 0.001 ns 0.01 ⬎ p ⬎ 0.001 ns
He edi as 148 (2011) Pea geno ypes, oo s and phospho us solubilisa ion 91
acquisi ion obse ed on he p ima y oo s in Line on No d
migh bene i a plan in an unp edic able en i onmen and
in he neighbou hood o o he geno ypes o he popula ion
whe e he plan happened o ge mina e. On he o he hand,
geno ypes e i cien a ce ain means o phospho us acqui-
si ion may cons i u e a gene ic load in ela ion o some
o he e ec s o he en i onmen . A empo al exp ession, a
72-h hy hm obse ed wi h Linie on No d migh mi iga e
any ad e se e ec o he p ope y. Many c ops a e g own
as mix u es o geno ypes. Mixed geno ypes ha a e able o
acqui e P om di e en sou ces migh p o e o be alu-
able in condi ions whe e soil P sou ces a e limi ing and
mul iple P subs ances a e ound in he soil.
Acknowledgemen s – We wan o hank M . Ka i Valkosaa i
(Honkajoki Oy, Honkajoki, Finland) o he sample o mea
bone meal and M . Jouko Nieminen (Kemphos Oy, he o me
Kemi a G owHow, Siilinj ä i, Finland) o he sample o apa i e.
The wo k by Ms. Eila Heikkil ä , MSc, was made possible h ough
he auspices o he Minis y o Labou , Finland.
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4 was low o e a wide pH ange in
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