Garcia, Jean-Louis

Vancura, V.

Horizon / Pleins textes

4 
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ROOT EXUDATES OF REVERSIBLY 
WILTED MILLET PLANTS -- --__I-.---_ 
(PANIC UM MIL IA CE UM L.) 2; ? . 3.\4 
--.. . -, . . , 3  
.--7 -. , 3- - .au,.= 
” -  v-- V. VANCURA and J.-L. GARCIA * 
Department o f  Soil Microbiology, Institute o f  Microbiology, 
Czechoslovak Academy of Sciences, Praha 4 
SUMMARY 
Exudation of various substances by millet plant roots (Panicum miliaceum L.), was 
compared in plants reversibly wilted and plants that were not affected by a moisture lack. 
The plants reversibly wilted exuded by 53 per cent more exudates, from which the content 
of a-aminonitrogen was by 190 per cent higher, of reducing sugars by 113 per cent higher, 
and of reducing substances by 50 per cent higher. The content of fructose, glutamic acid, 
a-alanine, valine and leucines increased essentially in root exudates of reversibly wilted 
plants as compared to the same weight unit. 
RÉSUMÉ 
Exsudats racinaires du millet après flétrissement réversible 
Nous avons comparé l’exsudation de diverses substances par les racines de plantules de 
millet (Panicum miliaceum L.), dans le cas de plantes flétries de façon réversible et de plantes 
non affectées par un manque d’eau. Les plantules flétries önt exsudé 53 % fois plus 
d’exsudats que les témoins, leur teneur en azote a-aminé étant supérieure de 190 %, celle 
des sucres réducteurs de 113 % et celle des substances réductrices de 50 %. Pour une même 
quantité d’exsudats, les teneurs en fructose, acide glutamique, a-alanine, valine et leucines 
ont nettement augmenté dans les exsudats racinaires des plantes, après flétrissement réversible. 
ZUSAMMENFASSUNG 
Die Wurzelausscheidungen der vorubergehend welkenden Hirsepflanzen 
Die Ausscheidung verschiedener Stoffe durch Wurzeln einerseits von vorübergehend 
welkenden Hirsepflanzen und anderseits von Pflanzen mit genügender Wasserversorgung, wurde 
verglichen. Die vorübergehend welkenden Pflanzen schieden um 53 % mehr Ausscheidungen 
(davon a-Amino-Stickstoff um 190 % , reduzierende Zucker um 113 % und reduzierende 
Stoffe um 50 %) aus. Bei der Umrechnung auf die gleiche Gewichtseinheit erwies sich der 
Gehalt von Fruktose, Glutaminsäure, %-Alanin, Valin, und der Leucine in den Wurzelaus- 
Scheidungen der vorübergehend welkenden Pflanzen wesentlich höher. 
* Present address : Laboratoire de Microbiologie des Sols, Centre O.R.S.T.O.M. de Dakar- 
Harm. B .P .  1386, Dakar (Sénégal). 
(ECOL. PLANT. 
G A ~ ~ ~ I E R - V I L L ~ , ~  *., - n. ^^ 
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94 V. VANCURA AND J.-L. GARCIA 
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KATZNELSON, ROUATT and PAYNE (1954) reported an increased exudation 
of aminoacids in barley, oat, tomato, anà soybean plants after desiccation and 
remoistening. We made use of this phenonienon in some of our experiments, in 
order to obtain a higher amount of root exudates, that were applied as nutrition 
and energy source in nutrient media for growing of microorganisms (VANCURA 
and MACURA, 1961; VANCURA, STANEK and HANZLIKOVA, 1969). This paper is 
giving data on quantitative and qualitative differences in exudates from plants thus 
treated. 
MATERIALS AND METHODS 
PLANT CULTIVATION 
Seeds of millet (Panicum miliaceum L., varietas " Hanácké ") were sterilized 
on their surface with mercuric chloride (VANCURA, 1964) and seeded in 3 cm layer 
of washed sterile silica sand in glas boxes (diameter 10 cm, height 7 cm). The boxes 
were placed in SHERER'S plant growth ,chamber Model CEL 2574% at 20-22 "C 
for a fortnight. Half a number of these boxes were opened thereafter and the plants 
were cultivated for 32 hours at 24 "C till they wilted slightly. The other plants in 
closed boxes kept a normal turgor. The wilted plants were remoistened (to original 
weight), and their cultivation continued for another 16 hours (in light for 4 hours, 
and in oscurity for the rest). 
. 
ISOLATION OF ROOT EXUDATES 
Over-ground parts of plants together with seed remainders were detached and 
a sand layer, forming together with roots a block was placed on Büchner funnel 
and washed with 100 ml distilled water. The eluate obtained was used for washing 
of another sand block and thus it has been continually enriched by root exudates 
from other boxes used in experiment. The eluates from both variants (control and 
reversibly wilted plants) were centrifugated (4 O00 revolutions/min.) and then 
these pellucid eluates were freezed and lyophilized. The lyophilizate was homo- 
genized in a rubbing bowl to a powder and stored in exicator to be used for various 
analysis later. 
95 ROOTS EXUDATES OF REVERSIBLY WILTED MILLET PLANTS 
\. ANALYSIS OF ROOT EXUDATES 
Most of the methods used were described in previous papers (VANCURA, 1964; 
VANCURA and HOVADIK, 1965)) a-Aminonitrogen was determined as to ROSEN 
(1957), reducing sugars by SOMOGYI and NELSON'S method (NELSON, 1944; SOMO- 
GYI, 1945). The amount of substances found in the exudates was calculated both 
per 1 O00 plants and per 1 g of exudates obtained. 
RESULTS AND DISCUSSION 
1) Analytical data on the exudation of plants reversibly wilted and control 
plants are given in the Table 1. Control plants exuded 50.8 pg, and reversibly 
wilted plants exuded 77.7 tLg of various substances per one plant during 16 days 
of cultivation. However, it is necessary to take into consideration that the substances 
TABLE 1 
Some analytical data on mot exudates of control and reversibly wilted plants 
Control 
plants 
Exudation per 1 O00 plants 
(in ms> 50.8 
Number of plants needed 
for 1 g of exudates 19 680 
Reducing substances 
in mg/l 000 plants 2.19 
Reducing substances 
in mg/g of root exudates 
Reducing sugars 
Reducing sugars 
(relative unit/weight unit) 236.0 
a-NH,-nitrogen in mg/ 
1 O00 plants 0.130 
a-NH,-nitrogen in mg/l g 
of root exudates 2.55 
43.09 
(relative unit/l O00 plants) 200.0 
Wilted 
plants 
77.7 
12 860 
3.30 
42.47 
426.0 
349.0 
0.377 
4.85 
Difference 
in % 
+ 52.9 
- 34.7 
+ 50.6 
- 1.5 
+ 113.2 
+ 47.9 
+ 190.0 
+ 90.1 
. *  -. 
. ,  
,.- , 
. .  . . .'" .; . . 
. .  . : . ,  
I -  
plants (*) 
Control plants 
96 V. VANCURA AND J.-L. GARCIA 
are not only exuded but also resorbed by pIant roots. Data are known (MESHKOV, 
1950; VANCURA, 1967), that the more frequently the exudates are determined 
during a certain period, the higher their total amounts is. Therefore, each amount 
of daily exudation per one plant that was calculated from records obtained in a 
longer period, can serve only for orientation. The Table 1 shows that plants 
reversibly wilted exuded almost by 53 per cent more exudates than control plants. 
2) Another our experiments showed that a difference in a quantity of exudates 
liberated decreased with a time of cultivation after wilting and remoistening. When 
the reversibly wilted plants were remoistened and cultivated for 3 days, their 
exudation was higher only by 6 per cent. It seems that in addition to others pheno- 
mena, an increased resorption of substances liberated before occurred, what was 
observed already in experiments on so called I' cold shock ", reported in a previous 
paper (VANCURA, 1967). Reversibly wilted plants liberated reducing substances 
by 50 per cent more, and amino-nitrogen by 190.per cent more than control plants. 
., 
- 
3) A calculation of these compounds per 1 g.of exudates showed that espe- 
cially what aminoacids were concerned, a change in their exudation was inadequate 
to the total increase in exudates. Analysing separately reducing sugars that formed 
only a part of reducing substances, the striking increase in exudation of reversibly 
wilted plants was observed; however, a change in exudation of sugars with respect 
to the total exudation was observed, too. A relative occurrence of particular sugars 
TABLE 2 
Relative incidence of reducing sugars in 15 mg of root exudates from millet 
Oligosaccharide, 
Oligosaccharide, 
Oligosaccharide, 
Oligosaccharide, 
Glucose 
Fructose + Arabinose 
Ribose 
Rhamnose 
Total 
Relative unit 
14 
73 
17 
71 
25 
17 
19 
236 
% 
5.93 
30.93 
7.20 
30.09 
10.60 
7.20 
8.05 
100.00 
Wilted plants 
Relative unit 
~ ~~ 
21 
64 
30 
90 
66 
28 
24 
323 
% 
6.50 
19.82 
9.29 
27.8 6 
20.43 
8.67 
7.43 
100.00 
(*) Area and density of the spots were recorded in relative units by 'I Direktschreiber 
mit Integrator '' (VEB Medizinische Gerätefabrik, Berlin). 
ROOTS EXUDATES OF REVERSIBLY WILTED MILLET PLANTS 97 
in the total amount of sugars changed too (Tab. 2). Glucose and some of oligo- 
saccharides were liberated in reversibly wilted plants in relatively lesser amount, 
and in contrast, fructose was exuded in larger amount than in control plants. 
Relative representation of other sugars almost didn't change. An increased exuda- 
tion of fructose, as compared to plants growing under normal conditions, was 
observed in plants subjected to a l1 cold shock 'I, too (VANCURA, 1967). In addition 
to sugars mentioned in the Tab. 2 also saccharose was found in exudates in both 
variants. 
The changes in the composition of aminoacids in the same weight units of 
exudates from control and reversibly wilted plants are given in the Tab. 3. I t  is 
of a great interest that the quantity of some aminoacids, such as basic amino acids, 
amides, cysteic acid, homocysteic acid, aspartic acid, serine, glycine, etc ... didn't 
change; some of them (threonine, proline, tyrosine, y-aminobutyric acid, phenyl- 
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TABLE 3 
Relative incidence of aminoacids in 3 mg of root exudates from millet plants 
Aminoacids Control plants 
Cysteic acid 
Homocysteic acid 
Ornithine 
Lysine 
Asparagine 
Glutamine 
Aspartic acid 
Serine 
Glycine 
or-Aminoadipic acid 
Glutamic acid 
Threonine 
or-Alanine 
Proline 
Tyrosine 
y-Aminobutync acid 
Valine (Methionine) 
Methionine sulphoxide 
Phenylalanine 
Leucine, isoleucine 
unidentified 
2 
2 
2 
2 
2 
2 
4 
2 
2 
1 
2 
1 
2 
1 
1 
4 
2 
1 
1 
2 
1 
Wilted plants 
2 
2 
2 
2 
2 
2 
4 
2 
2 
1 
4 
2 
5 
2 
2 
5 
5 
1 
2 
4 
2 u 
1 - 5 = area of spots (from traces to very large spots). 
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Root exudates of reversibly wilted millet plants (Panicum miliaceum L.)

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