ELECTRON PROBE ANALYSIS OF SAP EXUDATES OF TWO VARIETIES OF WHEAT (TRITICUM AESTIVUM L.)

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ELECTRON PROBE ANALYSIS OF SAP EXUDATES OF TWO VARIETIES OF WHEAT (TRITICUM

AESTIVUM L.)

S. Gartner, N. Roinel, N. Paris-Pireyre

To cite this version:

S. Gartner, N. Roinel, N. Paris-Pireyre. ELECTRON PROBE ANALYSIS OF SAP EXUDATES OF TWO VARIETIES OF WHEAT (TRITICUM AESTIVUM L.). Journal de Physique Colloques, 1984, 45 (C2), pp.C2-515-C2-518. �10.1051/jphyscol:19842117�. �jpa-00223785�

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Colloque C2, supplkrnent a u n02, Tome 45, f&vrier 1984 page C2-515

ELECTRON PROBE A N A L Y S I S OF SAP EXUDATES OF TWO V A R I E T I E S OF WHEAT

(TRITICUM ^{L L , )}

S. G a r t n e r , N . ~ o i n e l * and N. P a r i s - P i r e y r e

Laboratoire de PhysioZogie Vdge'tale, Universite' des Sciences e t Techniques du Languedoc, Place E. BataizZon, 34060 MoiztpeZ Zier Cedex, France

' ~ d ~ a r t e m e n t de BioZogie, Laboratoire de PhysioZogie Physico-Chimique, C . E . N . Saclay, 91191 Gif-sur-Yvette Cedex, France

Resume - La composition de l a seve du bl6 a 6 t e determinee par analyse a

l a microsonde 6lectronique.Cette technique a permis d ' a n a l y s e r quantitativement l e s elements K,Si ,P,C1 ,S Mg,Ca e t Na contenus dans l e s exsudats.

Abstract - The sap composition was determined by e l e c t r o n probe a n a l y s i s . With t h i s t e c h n i c s , i t has been p o s s i b l e t o make t h e q u a n t i t a t i - ve a n a l y s i s of t h e following elements:K,Si ,P,C1 ,S,Mg,Ca and Na contained i n t h e exudates.

In s p i t e of exudation experiments usually made,it i s very d i f f i c u l t t o reach t h e r e a l concentration of sap elements,for exudate volumes a r e very small and exuda- t i o n times cannot be too long.

As shown h e r e , t h e sap composition was determined by e l e c t r o n probe a n a l y s i s ( 1 ) The exudates were c o l l e c t e d under water s a t u r a t e d p a r a f f i n o i l . T h e concentration of the following elements: K,Si ,P ,Cl ,S ,Mg ,Ca and Na were measured,from 0.2 nl micro- drops,with a Cameca MBX e l e c t r o n probe a n a l y s e r ( l 2 kV,50-100 nA,beam diameter:90-100 um).Concentrations a r e expressed i n mmol.1 (mM).Thosemeasures c o n s t i t u t e a f i r s t experimentation i n t h e case of p l a n t m a t e r i a l .

1 - Comparison between c u l t u r e s o l u t i o n and sap.Evolution with time.

A f i r s t experiment was made with t h e "521" v a r i e t y , d u r i n g which t h e sap was c o l l e c t e d every hour during 5 hours.The wheat seedlings,two week o l d , a r e grown i n t h e Knop's c u l t u r e s o l u t i o n , t o which i s added 0.2 (mM) sodium s i l i c a t e . T h e exudation process i s then s t a r t e d i n t h e same solution(which has a pH of 5 . 5 ) .

exudate elements .

H i n d i c a t e a t what time t h e sap was c o l l e c t e d vol i s t h e volume ( ~ 1 ) of hourly exudates.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842117

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C2-516 JOURNAL DE PHYSIQUE

Some elements a r e found i n t h e sap a t h i g h e r c o n c e n t r a t i o n t h a n i n t h e c u l t u r e s o l u t i o n , f o r example potassium:30-45 (mM) ,p h o s p h o r u s , s i l i c o n and c h l o r i n e : 3 t o 8

mM . C o n c e n t r a t i o n s o f s o d i u m , s u l f u r and magnesium a r e v e r y c l o s e t o t h o s e o f t h e c u l t u r e s o l u t i o n , a n d t h e r e f o r e presumably f o l l o w t h e w a t e r f l o w i n t h e r o o t s . 0 n t h e c o n t r a r y , c a l c i u r n i s found a t a l o w e r c o n c e n t r a t i o n i n t h e sap t h a n i n t h e s o l u - t i o n ( t a b 1 e 1).

The exuded volumes a r e l a r g e d u r i n g t h e f i r s t , a n d m a i n l y ,the second hour,and then seem t o s t a b i l i z e , o r e v e n t o decrease s l i g h t l y so t h a t , i n s p i t e o f t h e v a r i a - t i o n s of c o n c e n t r a t i o n s w i t h t i m e , t h e h o u r l y exuded amount remain c o m p a r a b l e , p a r t i - c u l a r l y a f t e r t h e t h i r d hour.

2 - E f f e c t o f c u l t i v a t i o n c o n d i t i o n s on sap c o n c e n t r a t i o n i n t h e case of "521" andnTarasque" v a r i e t i e s .

I n t h i s s e r i e s of experiments,the 2-week o l d p l a n t s a r e grown and exuded i n Knop's s o l u t i o n , w i t h o r w i t h o u t a d d i t i o n o f sodium s i l i c a t e a t v a r i o u s c o n c e n t r a - t i o n s . A f t e r two hours and a h a l f , t h e exudate i s c o l l e c t e d and discarded.Then,the exudate o f t h e f o l l o w i n g 30 m i n u t e s i s c o l l e c t e d f o r a n a l y s i s . I n t h a t way,the exuda- t i o n has most 1 i k e l y reached t h e s t a b i l i z e d stage.

2.1 - I n f l u e n c e o f t h e s i l i c o n o f t h e c u l t u r e s o l u t i o n

lo 9 8 7 6 5 4 3 2 . 1

a b c d e

1 s i l i c o n i n t h e s o l u t i o n : - 0 ⁵²¹

-

Tarasque

-

- -

-

- - -

d

F i g u r e 1 . S i sap c o n c e n t r a t i o n (mM) (Means v a l u e s + s.e.m.,n=3)

.The s i l i c o n c o n t e n t i n t h e sap i n c r e a s e s w i t h t h e s i l i c o n c o n t e n t i n t h e so- l u t i o n ( f i g . l ) .

. P l a n t s grown w i t h o u t s i l i c o n show a s m a l l amount of i t i n t h e i r sap(O.ZrnM), which i s p r o b a b l y coming from e i t h e r t h e s i l i c o n o f t h e p l a n t i t s e l f , o r a p o l l u t e d c u l t u r e s o l u t i o n ( d u s t , i m p u r i t i e s i n b i d i s t i l l e d w a t e r ) .

.The s i l i c o n amount i s g r e a t e r i n t h e "521" sap t h a n i n t h e "Tarasque" sap.

The d i f f e r e n c e i n c r e a s e s w i t h t h e S i c o n c e n t r a t i o n o f t h e c u l t u r e s o l u t i o n .

.The s i l i c o n c o n t e n t o f t h e e x u d a t i o n s o l u t i o n has an i m p o r t a n t e i n f l u e n c e on t h a t o f t h e sap w i t h i n t h e t h r e e hours process s t u d i e d here:

- i n c r e a s e i n t h e case o f p l a n t s grown w i t h o u t s i l i c o n and exuded i n a s o l u t i o n c o n t a i n i n g 0.05 mM s i l icon,or

-decrease when t h e e x u d a t i o n s o l u t i o n c o n t a i n s no s i l i c o n , i n t h e case o f p l a n t s grown on a + 0.05 mM S i s o l u t i o n .

These phenomena a r e observed i n b o t h wheat v a r i e t i e s .

o f e x u d a t i o n (mM) 0

0.05 0 0.05 0.2 o f c u l t u r e (mM)

a b c d e

0 0 0.05 0.05 0.2

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2.2 - V a r i a t i o n s o f elements c o n c e n t r a t i o n s w i t h t h e age o f t h e p l a n t s

F i g u r e 2 . Elements c o n c e n t r a t i o n s i n t h e sap o f 2-and 4-week o l d p l a n t s (Means v a l u e s + s e m, n=3)

f a b l e I 1 . C o n c e n t r a t i o n and amount o f s i l i c o n exuded by 2 and 4 week o l d p l a n t s (means values 2s e m).

F i g u r e 2 shows t h a t t h e K,P and C1 c o n c e n t r a t i o n s i n c r e a s e w i t h t h e age o f t h e p l a n t s . I n t h e 2-week o l d p l a n t s , t h e t h r e e elements a r e more c o n c e n t r a t e d i n t h e sap than i n t h e s o l u t i o n , a n d t h i s phenomenon i s more e v i d e n t w i t h t h e 4-week o l d plants.The w a t e r f l o w r a t e s a r e g r e a t e r a t 4 week t h a n a t 2 week and t h e t r a n s p o r t i s more i m p o r t a n t i n o l d e r p l a n t s . W i t h r e s p e c t t o t h e c u l t u r e s o l u t i o n , a n over-con- c e n t r a t i o n i n t h e sap i s reached w i t h t i m e ( t a b l e I 1 and f i g . 2 ) .

The s i l i c o n , w h i c h i s a l s o o v e r - c o n c e n t r a t e d i n t h e sap o f 2-week o l d p l a n t s , remains more c o n c e n t r a t e d i n t h e 4-week o l d p l a n t s , b u t w i t h a sap c o n c e n t r a t i o n a l - most d i v i d e d i n half.However,table I 1 shows t h a t i t s exuded amount i s n e v e r t h e l e s s g r e a t e r a t 4 week than a t 2 week.

I n t h e case o f s u l f u r , i t s c o n c e n t r a t i o n i s c l o s e t o t h a t o f t h e c u l t u r e s o l u - t i o n i n 2-week o l d ~ l a n t s , w h i l e i t seems t o o v e r - c o n c e n t r a t e , i n comparison t o t h e c u l t u r e s o l u t i o n , i n t h e 4-week o l d p l a n t s .

L a s t l y , t h e r e s u l t s a r e more v a r i a b l e i n t h e case o f calcium,sodium and magnesium.

2.3. I n f l u e n c e o f t h e pH o f t h e c u l t u r e s o l u t i o n .

Two-week o l d p l a n t s o f t h e "521" v a r i e t y a r e grown and exsuded i n h a l f d i l u t e d Knop's s o l u t i o n , c o n t a i n i n g 1mM sodium s i l i c a t e , p H o f which i s s e t a t 6,0r a t 7.5.

Tarasque ⁺

2 week 4 week

3.56 t 0 . 5 1 2.03 t0.87

0.89 20.55 9.12 24.12

0.25 t 0 . 2 1 4.5 21.2 521

2 week 4 week

C o n c e n t r a t i o n

The s i l i c o n c o n c e n t r a t i o n i s t h e o n l y one t o be g r e a t e r i n t h e pH 7.5 s o l u t i o n t h a n i n t h e pH 6 one ( f i g . 3).The c o n c e n t r a t i o n s o f t h e o t h e r elements remain unchan- ged (P,S,Mg) ,or decrease (K,C1 ,Ca,Na).

7

(mM) amount

(mmo 1) exudate v o l umes

( ~ 1 )

3 . 8 3 2 1 . 1 4 1 . 9 6 + 1 . 0 1.43 20.88 10.08 24.12

0.35 $0.21 4.7 50.43

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F i g u r e 4. P c o n c e n t r a t i o n ( m ~ 1 ) v e r -

K 9 P CI S Mg Ca Na sus S i i n c u l t u r e s o l u t i o n . (means v a l u e s + sem) F i g u r e 3.Sap c o n c e n t r a t i o n v e r s u s pH o f

c u l t u r e s o l u t i o n ( m e a n s v a l u e s 2 sem). a: and in "lu-

(n=3) t i o n + S i ( 0 mM)

b: c u l t u r e and e x u d a t i o n i n s o l u - t i o n + S i (0.05 mM)

c: c u l t u r e and e x u d a t i o n i n s o l u - t i o n + S i (0.2 mM).

2.4 I n f l u e n c e o f s i l i c o n on phosphorus a b s o r p t i o n

When t h e r e i s s i l i c o n i n t h e c u l t u r e s o l u t i o n , t h e P c o n c e n t r a t i o n o f t h e sap i n c r e a s e s ( f i g 4) .But i t s h o u l d be n o t e d t h a t t h e a d d i t i o n o f s i l i c a t e b r i n g more sodium i n t h e s o l u t i o n . I n t h e case o f f i g . 4 - B e (experiments on "521" v a r i e t y o n l y ) , t h e c u l t u r e s o l u t i o n s w i t h o u t s i l i c a t e r e c e i v e sodium s u l f a t e i n such a n amount t h a t t h e Na c o n c e n t r a t i o n i s t h e same i n t h e s o l u t i o n s w i t h o r w i t h o u t s i l i c o n . I t can be n o t i c e d t h a t t h e wheat grown w i t h o u t s i l i c o n t a k e s more phosphorus t h a n i f grown w i t h ri1ica.However t h i s d i s c r e p a n c y i s l e s s c l e a r t h a n t h a t o f f i g 4.Therefo- re,Na can be t h o u g h t t o p l a y a g r e a t e r r o l e t h a n S i i n t h e i n c r e a s e o f P c o n c e n t r a t i o n when c u l t u r e s o l u t i o n c o n t a i n s sodium s i l i c a t e .

3 . C o n c l u s i o n

With o u r t e c h n i c s , i t has been p o s s i b l e t o make,on each sample,the q u a n t i t a t i v e a n a l y s i s o f t h e m a i n elements c o n t a i n e d i n t h e sap.These experiments have p r i n c i p a l - l y demonstrated t h a t m i c r o s a m p l i n g s a r e q u i t e f e a s i b l e and t h a t t h e elements t h e y c o n t a i n a r e i n adequate c o n c e n t r a t i o n t o be determined w i t h t h e e l e c t r o n probe ana- l y s e r .

A l t h o u g h t h e v a l u e s a r e r a t h e r v a r i a b l e due t o t h e l o w number o f t e s t e d sam- p l e s , t h o s e f i r s t experiments show t h a t i t i s c o n s e q u e n t l y p o s s i b l e t o s t u d y t h e appearance i n t h e sap,and hence,tbe a b s o r p t i o n and t h e conveyance,of a r a t h e r l a r g e number o f elements i n a g i v e n sample,according t o d i f f e r e n t pararneters:age o f p l a n t s v a r i e t i e s , c o n d i t i o n s o f c u l t u r e . . . .

F i n a l l y , t h e a b i l i t y t o a n a l y s e v e r y s m a l l volumes o f l i q u i d s opens t h e way t o sampling exudates c o l l e c t e d w i t h i n a v e r y s h o r t time.This would a l l o w t o reduce t h e way t h e r o o t s a r e a f f e c t e d b y b o t h e x c i s i o n and l a c k o f a e r i a l p a r t s - I t would a l s o make i t p o s s i b l e t o r e a c h a sap c o m p o s i t i o n as c l o s e as p o s s i b l e t o t h a t of t h e whole p l a n t .

( 1 ) - MOREL F. and ROINEL N. J. Chjm. Phys. - 66 (1969).1054-1092