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Annals of Biological Research, 2011, 2 (2) : 414-422
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ISSN 0976-1233
CODEN (USA): ABRNBW
Soybean nodulation and chlorophyll concentration (SPAD value)
affected by some of micronutrients
Soheil Kobraee*, Keyvan Shamsi and Siros Ekhtiari,
Department of Agronomy and Plant Breeding, Islamic Azad University, Kermanshah Branch,
Kermanshah, Iran
______________________________________________________________________________
ABSTRACT
There were relationships between Chlorophyll concentration, nodulation and quality and
quantity traits in soybean and micronutrients have effects on these relationships. In order to
study some of these effects, the pot experiment was done at the research field of the Islamic Azad
University of Kermanshah province, Iran in 2010. The experimental design was a 3×3×3
factorial experiment based on Randomized Complete Block with three replicates. The experiment
consist of 27 treatments included of three rates of Zinc (0, 4, and 8 mg Zn kg-1 as ZnSo4.7H2o),
three rates of iron (0, 4, and 8 mg Fe kg-1 as FeSo4), and three rates of manganese (0, 15, and 30
mg Mn kg-1 as MnSo4.4H2o). At 48 days after sowing and before harvesting, The SPAD-502
meter reading were performed on 5 leaves per experimental pot and then plants were harvested.
Number of nodule per plant and fresh weight were determined, after drying, mass nodules and
shoot dry weight were measured. The results shown that, there were significant differences in the
number, fresh & dry weight of nodules per plant different levels of Zinc, Iron and manganese
application. plant height was not affected by Zn and interaction effects of Zn and Fe. The
maximum number of nodules per plant was obtained from 4, 8 and 30mgZn, Fe and Mn per kg
soil, respectively. Maximum plant height, total dry weight and SPAD value were obtained in
Zn4Fe8Mn30 with 46.8(cm), 3.37(gr), and 31.9, respectively.
Key word: chlorophyll, micronutrient, nodulation, soybean, SPAD value.
_________________________________________________________________
INTRODUCTION
Among environmental factors, nutrients availability within plants can be critical limitations on
plant production. Micronutrients, known as trace elements that are required in small quantities by
plants. Micronutrients deficiency such as Zinc, Iron and Manganese were limited growth [11, 12,
14], symbiosis and nodulation [1, 5, 14, 35, 38, 42], photosynthesis [1, 3, 22, 38], chlorophyll
concentration [2, 16, 28, 31, 32, 40], dry matter accumulation [2, 5, 14, 16], and plant nutrient
imbalanced [9, 10, 24]. Soybean is one of the non-conventional oilseed legume crops of the
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world. Worldwide, it is estimated that leguminous plants are fixing 80 million tones of nitrogen
annually from the vast free supply in the air. In contrast fertilizer manufactures produce at high
cost only 50-60 million tones of nitrogen annually [13]. [26] Stated that soybean plants fix more
than 276 hg of nitrogen/ha in the aboveground plant parts. Nitrogen accumulation rates average
between 3300-7800 grams/ha/day during reproductive development. Research showed that
inoculation of seed increased the plant height, photosynthetic rate, plant biomass, number, dry
and fresh weight of nodules per plant and yield components of soybean as compared with noninoculated control [4, 7, 18, 21, 33]. Leaf total chlorophyll concentration, decreased with Zn, Mn
and Fe deficiency [2]. Metals such as Zn, Fe and Mn are required in the biosynthetic pathway of
chlorophyll. These metals are involved directly in electron transport reactions and are essential
for the synthesis of of chlorophyll [2, 28, 31]. [16] Reported that chlorophyll (SPAD 502) values
were greater when Mn and Zn were added to the soil than the 0 ppm treatment. Research on the
effects of Zn, Fe, Mn and interaction it's on soybean nodulation and chlorophyll (SPAD 502)
values is limited. [5] Reported that soybean nodulation unaffected by Zinc application that
research was shown that the highest number of nodules obtained to 20kgZnha-1, while dry matter
and shoot biomass were significantly affected by Zinc application. Zinc application increased
nodules formation in soybean [42]. [1] Stated that in nodules of legumes, Fe is an essential for
leghaemoglobin biosynthesis that transported oxygen within cells. Results of [20] was shown
that Fe and Mn concentration up to 50 µm in solution were not affected on root, shoot and nodule
mass. In that experiments, chlorophyll concentration in soybean leaves with added of Mn was
increased. Based on [41] studies, using from SPAD 502 for the estimation of chlorophyll content
in leaves was more useful method as compared to the extraction method. Research on the effects
of Zn, Fe, Mn and interaction effects on soybean nodulation and chlorophyll concentration are
limited. Therefore, the objective of this study was to evaluation the effects of Zn, Fe and Mn
applied on the number and weight of nodules in roots, shoot biomass and chlorophyll
concentration (SPAD value) in soybean in climatic conditions of Kermanshah, Iran.
MATERIALS AND METHODS
The experiment was done at the research field of the Islamic Azad University of Kermanshah
province, Iran (34023' N, 4708' E; 1351 m elevation) in 2010. The experimental design was a
3×3×3 factorial experiment based on Randomized Complete Block with three replicates. Surface
soil was collected from an agricultural field and passed through a 2-mm mesh screen. The texture
of the soil based on silty clay with pH 7.6, total organic matter 1.8%, electrical conductivity
(ECe) 0.46 dsm-1, total nitrogen 0.09%, available phosphorus 7.4 mg kg-1, available potassium
435 mg kg-1, zinc, iron and manganese 0.56, 5.1 and 3.2 mg kg-1, respectively. The experiment
consist of 27 treatments included of three rates of Zinc (0, 4, and 8 mg Zn kg-1 as ZnSo4.7H2o),
three rates of iron (0, 4, and 8 mg Fe kg-1 as FeSo4), and three rates of manganese (0, 15, and 30
mg Mn kg-1 as MnSo4.4H2o). All pots were fertilized with 20 mg N kg-1 as NH4NO3, 40 mg P
kg-1 as H2PO4.2H2O. Six seeds of soybean (cv. Williams) inoculated with BradyRhizobium
japonicum and were sown directly in plastic pots containing 4 kg of the soil. After 48 days,
plants were harvested and samples were washed in deionized water. For measure of dry weight,
samples were dried oven at 700Cand 48 hours. Nodules are removed from the roots and number
of nodule per plant and fresh weight were determined, after drying, mass nodules were
measured. At 48 days after sowing and before harvesting, The SPAD-502 meter reading were
performed on 5 leaves (from the uppermost leaf of youngest fully developed trifoliate leaf) per
experimental pot for all replicates. All of data obtained from the measurements and analyses
were evaluated statistically by the analysis of variance and F-test means comparison conducted
by least significant difference (LSD) test. Correlation coefficient significance was evaluated by
student’s t-test.
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RESULTS AND DISCUSSION
The results of analysis of variance were shown in Table1. There were significant differences in
the number, fresh & dry weight of nodules per plant different levels of Zinc, Iron and manganese
application. In addition, effects of Fe and Mn on plant height was significant, likewise, plant
height was not affected by Zn and interaction effects of Zn and Fe (Table1). [40] Stated that
plant height of soybean increased when that Fe was applied. The simple effect of these elements
was shown in Figure1. The maximum number of nodules per plant was obtained from 4, 8 and
30mgZn, Fe and Mn per kg soil, respectively.
The results was shown that with application of zinc up to 4 mgkg-1 soil fresh and dry weight of
nodules per plant were increased and then decreased (Fig1). [5, 42] Stated that zinc application
increased nodules formation and shoot biomass in soybean. Shoot dry weight was not affected by
zinc application but with application of Zn up to 8mgkg-1soil shoot dry weight was decreased
(Table1).
Research of [17] indicated that Mn and Zn application were increased biomass accumulation, but
were not affected number of nodules and nodule mass per plant in soybean. In nodules of
legumes, iron is an essential for leghemoglobin biosynthesis, that transported oxygen within
cells. Nodule formation in soybean is very sensitive process to Fe deficiency [19]. SPAD value
affected by zinc, iron and manganese application and there was significant differences between
different levels of these micronutrients application (P<0.01). Zn, Fe, and Mn increased
chlorophyll concentration, as measured with a SPAD-502 meter.
In the zinc study, chlorophyll content at 4mgZnkg-1 soil increased, but with excess decreased.
[16] Found that chlorophyll values (SPAD- 502) were greater when Mn and Zn were added to
the soil. With application of iron up to 8 mg per kg soil, SPAD values were increased. The
highest SPAD values belonged to 30mgkg-1soil 1Mn (Fig1).
The interaction effects of these elements were shown in Table1. Except of plant height and shoot
dry weight, interaction effects of these elements on fresh & dry weight of nodules per plant
(P<0.01) and SPAD value (P<0.05) were significant. The highest number, fresh and dry weight
of nodules per plant were found in Zn0Fe4Mn30 mgkg-1soil with 27.3, 1.70(gr), and 0.41(gr),
respectively. Maximum plant height, total dry weight and SPAD value were obtained in
Zn4Fe8Mn30 with 46.8(cm), 3.37(gr), and 31.9, respectively. [2] Reported that in zinc, iron and
manganese deficiency conditions, Leaf chlorophyll concentration was decreased. Metal such as
Zn, Fe and Mn are required in the biosynthetic pathway and essential for the synthesis of
chlorophyll [28, 31, 40].
The lowest SPAD value was obtained at Zn0Fe0Mn0 treatment. Based on Table 3, there were
highly significant positive correlation between number of nodules per plant and shoot dry weight
(r=0.525**) and SPAD value (r=0.661**). There is a significant positive correlation between
shoot dry weight and SPAD value (r=0.731**).
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Number of
nodule per
plant
Number of
nodule per
plant
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Iron fertilizer(mgkg-1 soil)
Fersh weight
of nodule
(gr.plant-1)
Number of
nodule per
plant
Zinc fertilizer(mgkg-1 soil)
Manganese fertilizer(mgkg-11 soil)
Fersh weight of
nodule
(gr.plant-1)
Fresh weight of
nodule
(gr.plant-1)
Zinc fertilizer(mgkg-1 soil)
Manganese fertilizer(mgkg-1 soil)
Dry weight of
nodule (gr.plant-1)
Dry weight of
nodule (gr.plant-1)
Iron fertilizer(mgkg-1 soil)
Zinc fertilizer(mgkg-1 soil)
Dry weight of
nodule (gr.plant-1)
Height of plant
(cm
Iron fertilizer(mgkg-1 soil)
Zinc fertilizer(mgkg-1 soil)
Manganese fertilizer(mgkg-1 soil)
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Height of plant
(cm
Height of plant
(cm
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Manganese fertilizer(mgkg-1 soil)
Shoot dry
weight
(gr.plant-1)
Shoot dry
weight
(gr.plant-1)
Iron fertilizer(mgkg-1 soil)
Zinc fertilizer(mgkg-1 soil)
Shoot dry
weight
(gr.plant-1)
SPAD
Reading
Iron fertilizer(mgkg-1 soil)
Zinc fertilizer(mgkg-1 soil)
SPAD
Reading
SPAD
Reading
Manganese fertilizer(mgkg-1 soil)
Iron fertilizer(mgkg-1 soil)
Manganese fertilizer(mgkg-1 soil)
Figure1. Effect of Zinc, Iron and manganese on number of nodule per plant, fresh and dry weight of nodule
per plant, plant height, shoot dry weight and SPAD reading in soybean.
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Table1. Analysis of variance of soybean evaluated traits
Source of
variation
Block
Zn
Fe
Zn×Fe
Mn
Zn×Mn
Fe×Mn
Zn×Fe×Mn
Error
Coefficient of variation (%)
d.f
2
2
2
4
2
4
4
8
52
-
NNP
3.21
115.68**
227.29**
57.96 **
106.64 **
10.27 **
35.09 **
12.39 **
2.58
7.68
FWN
0.02
0.19**
0.81**
0.16**
0.39**
0.07 **
0.11 **
0.09 **
0.02
11.33
MS
DWN
0.002
0.024**
0.037**
0.017**
0.011**
0.007*
0.014**
0.005**
0.002
9.30
H
0.23
43.35 ns
338.61**
17.12 ns
120.97**
9.56 ns
31.74 ns
4.39 ns
15.94
10.60
SDW
0.16
2.51 ns
5.72**
0.32*
3.49**
0.21ns
0.94**
0.18ns
0.09
13.19
SPAD
3.45
62.93**
146.03**
18.36**
87.45**
2.07ns
1.55ns
4.86*
1.98
5.51
-ns, * and ** : Non significant, significant at 5 and 1% levels of probability, respectively
-NNP: Number of nodule per plant; FWN: Fresh weight of nodule per plant; DWN: Dry weight of nodule per plant;
H: Plant height; SDW: Shoot dry weight, and SPAD: SPAD value.
Table2: Mean comparison Number of nodule per plant; Fresh weight of nodule per plant; Dry weight of
nodule per plant; Plant height; Shoot dry weight, and SPAD value in soybean according to LSD test in %5
level
Rate of fertilizer
Means
(kg/ha)
Zn
Fe
Mn
NNP
FWN
DWN
H
SDW
SPAD
0
0
0
12.1 j
0.72 g
0.16 hij
32.6 hi
1.45 i
20.3 m
0
0
15
11.7 j
0.70 g
0.13 ij
32.8 hi
1.60 ghi
21.7 lm
0
0
30
14.2 ij 0.75 g
0.11 j
31.7 i
1.52 hi
22.5 klm
0
4
0
18.5 gh
1.07cdef
0.21 defgh 33.5 fghi
1.49 hi
21.0 lm
0
4
15
16.8 hi
1.01def
0.22cdefgh 38.5bcdefgh 1.72 fghi
23.2 jkl
0
4
30
27.3 a
1.74 a
0.41 a
40.1 bcde
2.21 de
27.2 def
0
8
0
21.4 de
1.08cdef
0.24bcdefg 37.6cdefghi 2.12 def
25.4 fghij
0
8
15
26.3 ab
1.37 b
0.28 bcd
39.4 bcdefg 2.71 bc
27.8 cde
0
8
30
20.5 efg
1.25 bc
0.29 bc
39.6 bcdef
2.26 cd
28.4 bcd
4
0
0
18.7 fgh
1.18bcde
0.29 bc
33.0 ghi
1.75 efghi 21.7 lm
4
0\
15
21.6 de
1.03def
0.28 bcd
33.5 fghi
1.87defghi 24.3 ijk
4
0
30
24.8 abc
1.11cdef
0.23cdefgh 33.7 efghi
1.52 hi
24.1 ijk
4
4
0
18.7 fgh
0.98ef
0.19 fghi
33.0 ghi
1.68 fghi
25.6 efghi
4
4
15
21.5 de
1.09cdef
0.27 bcde
42.4 abc
3.07 ab
29.7 abc
4
4
30
26.1 ab
1.35 b
0.29 bc
40.5 abcd
2.97 ab
30.2 ab
4
8
0
22.7 cde
1.12cdef
0.27 bcde
38.5bcdefgh 2.28 cd
27.0 defg
4
8
15
25.5 ab
1.19bcd
0.25bcdefg 44.3 ab
3.15 ab
30.1 abc
4
8
30
26.4 ab
1.72 a
0.31 b
46.8 a
3.37 a
31.9 a
8
0
0
17.3 h
0.98ef
0.19 fghi
35.2 defghi
2.03 defg
21.7 lm
8
0
15
16.5 hi
0.68 g
0.13 ij
35.1 defghi
2.09 defg
24.4 hijk
8
0
30
21.4 de
1.02def
0.19 fghi
36.7cdefghi 1.97 defgh 26.7 defgh
8
4
0
23.8bcd
1.10cdef
0.22cdefgh 35.2 defghi
1.71 fghi
24.8 ghijk
8
4
15
21.2 def
0.96 f
0.19 fghi
39.6 bcdef
2.99 ab
25.1 fghij
8
4
30
25.4 ab
1.17bcde
0.26bcdef
42.8 abc
3.10 ab
26.1defghi
8
8
0
20.7 efg
1.18bcde
0.29 bc
38.8bcdefgh 2.01 defg
24.3 ijk
8
8
15
21.2 def
1.17bcde
0.18 ghij
40.4 abcd
3.03 ab
27.8 cde
8
8
30
22.1 de
1.09cdef
0.20 efghi
41.6 abcd
3.08 ab
26.2defghi
-Similar letters in each column shows non-significant difference according to LSD test in %5 level.
-NNP: Number of nodule per plant; FWN: Fresh weight of nodule per plant (gr.plant-1); DWN: Dry weight of
nodule per plant (gr.plant-1); H: Plant height (cm); SDW: Shoot dry weight (gr.plant-1); and SPAD: SPAD value.
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Table3. Pearson correlation coefficients among evaluated traits in soybean
NNP
1.00
FWN
NNP
DWN
H
SDW
FWN
0.746**
1.00
DWN
0.645**
0.747**
1.00
H
0.485*
0.480*
0.361*
1.00
TDW
0.525**
0.445*
0.293ns
0.707**
1.00
SPAD
0.661**
0.598**
0.393*
0.633**
0.731**
SPAD
1.00
-ns, * and **: Non significant, significant at 5 and 1% levels of probability, respectively
-NNP: Number of nodule per plant; FWN: Fresh weight of nodule per plant (gr.plant-1); DWN: Dry weight of
nodule per plant (gr.plant-1); H: Plant height (cm); SDW: Shoot dry weight (gr.plant-1); and SPAD: SPAD value.
Acknowledgments
The authors wish to thank from The Islamic Azad University for supporting projects. This
research was supported by Islamic Azad University, Kermanshah Branch, Kermanshah, Iran.
CONCLUSION
The legume-rhizobia symbiosis is particularly sensitive to nutrients deficiency. Rhizobium
japonicum is one of important species of genus Rhizobium which infect the root of soybean
plant. Research showed that inoculated of seed soybean with this bacteria increased the plant
height, photosynthetic rate, plant biomass and dry weight of nodules [4, 7, 18], Whereas, other
researcher such as [29, 37] Reported that seed inoculation had no effect on nodule formation,
nodule number and plant biomass. The main product of symbiosis nitrogen fixation in soybean
root nodules is ureides [36]. Soybean transports of this ureides to the plant shoot, manganese is a
cofactor required in the catabolism of the ureides in the leaves [34]. In nodules of soybean, Iron
is an essential for leghaemoglobin biosynthesis that transported oxygen within cells [1]. Zinc is
an important role as a functional, structural and regulatory cofactor of a large number of enzymes
[23]. Also leaf chlorophyll content in plants were adversely affected by Zinc deficiency. In this
experiment was used from the SPAD 502 for the measurement of the chlorophyll content in
soybean leaves that were used as a diagnostic tool for the evaluation of plant nutrients, such as
iron, manganese, nitrogen, magnesium and other micronutrients related to chloroplast pigment
contents. Many researches were conducted on the usefulness of SPAD 502 as a nondestructive
analysis method for determination of chloroplast pigments [6, 8, 15, 25, 27, 30, 39]. In this
experiment, using Zinc, Iron and Manganese increased the evaluated traits the highest value of
which obtained by application 4, 8 and 30 mg per kg soil Zinc, Iron and Manganese.
REFERENCES
[1]-Abdelmajid, K., and Chedly, A. Journal of Plant Nutrition and Soil Science. 2003.166: 525528.
[2]-Adams, M. L., Norvell, W. A., Philpot, W. D., and Peverly, J. H.. Agron J. 2000. 92: 261268.
[3]-Ahlbrink, R., Semin B. K., Mulkidjanian. A. Y. & Junge, W. Biochimica et Biophysica Acta.
2001.1506: 117-126.
420
Scholars Research Library
Soheil Kobraee et al
Annals of Biological Research, 2011, 2 (2):414-422
_____________________________________________________________________________
[4]-Aslam, M., Mahmood, I. A., Sultan, T., and Ahmad, S. Pak. J. Biol. Sci. 2000. 3(2): 193-195.
[5]-Awlad H M, Chowdhury M A H and Talukder N M. Pakistan Journal of Biological Sciences.
2003. 6 (5): 461-466.
[6]-Azia, F., and Stewart, K. A. Journal of Plant Nutrition. 2001. 24 (6): 961-966.
[7]-Badawy, F. H., Mahmoud, S. M., Hassanein, H. G., and El-Desouky, M. M. Assiut J. Agric.
Sci. 1992. 23(1): 141-152.
[8]-Bonneville, M. C., and Fyles, J. W. Communication in Soil Science and Plant Analysis. 2006.
37 (3-4): 525-539.
[9]-Cenni, E., Bussotti, F., and Galeotti, L. Annuals Des Sciences Forestieres. 1998. 55: 567576.
[10]-De Varennes, A., Carneiro, J. P. and Goss, M. J. Journal of Plant Nutrition. 2001. 24: 19471955.
[11]-Fageria NK. (). Eng. Agri. Ambien. 2000. 4: 390-395.
[12]-Fageria NK. and Baligar VC. J. Plant Nutrition. 1997. 20: 1279-1289.
[13]-FAO. Legume inoculants and their use. Food and Agriculture Organisation (FAO) of the
United Nations. Rome, Italy. 1984. Fao Statistics Division.
[14]-Gholamalizadeh, A. A., Karimian, N., Abtahi, A., Assad, M. T., and Eman, Y. Commun.
Soil Sci. Plant Anal. 1995. 26, 1441-1454.
[15]-Girma, K., Martin, K. L., Anderson, R. H., Arnall, D. B., Brixey, K. D., Casillas, M. A., and
Chung, B. Journal of Plant Nutrition. 2006. 29 (5): 873-897.
[16]-Heitholt JJ, Sloan JJ, Mackown CT. Journal of Plant Nutrition. 2002. 25: 8, 1727-1740.
[17]-Heitholt J J, Sloan J J, MacKown C T and Cabrera R I. Journal of Plant Nutrition. 2003. 26:
4, 935-948.
[18]-Imsande, J. J. Expt. Bot. 1998. 39 (206): 1313-1321.
[19]-Izaguirre-Mayoral, M. L., and Sinclair, T. R. Journal of Plant Physiology. 2009. 166: 807818.
[20]-Izaguirre- Mayoral M L and Sinclair RT. Journal of Plant Nutrition. 2005. 28: 521-535.
[21]-Jain, N. K., Jain, H. C., and Khandkar, U. R. Ind. J. Agron. 1988. 33(4): 347-350.
[22]- Jiang, C. D., Gao. H. Y. & Zou. Q. Photosynthetica. 2002. 40: 209-213.
[23]-Kaya, C., and Higgs, D. Scientia Horticulturae. 2002. 93: 53-64.
[24]-Marschner, H. Mineral nutrition of higher plants. Academic Press. London. 1995.
[25]-Neves, O. S. C., De Carvalho, J. G., and Martins, F. A. D. Pesquisa Agropecuaria
Brasileira. 2005. 40 (5): 517-521.
[26]-Oplinger, E. S., Gaska, J. M., and Krantz, D. Agronomy Advice, Agron. Deptt. Univ.,
Wisconsin-Extension. 1999.
[27]-Parvizi, Y., Ronaghi, A., Mafton, M., and Karimian, N. A. Communication in Soil Science
and Plant Analysis. 2004. 35 (9-10): 1387-1399.
[28]-Pushnik, J. C., and Miller, G. W. J. Plant Nutr. 1984. 12: 407-421.
[29]-Qasim, M., Ahmad, K., Shah, N. Z., and Razaullah. A. Sarhad J. Agric. 1994. 10(3): 231236.
[30]-Sexton, P., and Caroll, J. Journal of Plant Nutrition. 2002. 25 (9): 1975-1986.
[31]-Spiller, S. C., A. M. Castelfranco., and Castelfranco, P. A. Plant Physiol. 1982. 69: 107111.
[32]-Teklic, T., Vrataric, M., Sudaric, A., Koracevic, V., and Vukadinovic, V. Communications
in Soil Science and Plant Analysis. 2009. 40: 706-725.
[33]-Thananusont, V., and Vithara. T. Kasetsart J. Nat. Sci. 1996. 30 (5): 165-170.
[34]-Todd, C. D., and Polacco, J. C. Journal of Experimental Botany. 2004. 55: 867-877.
[35]-Vadez, V., Sinclair, T. R., Serraj, R., and Purcell, L.C. Plant, Cell and Environment. 2000.
23: 497-505.
421
Scholars Research Library
Soheil Kobraee et al
Annals of Biological Research, 2011, 2 (2):414-422
_____________________________________________________________________________
[36]-Van Heerden, P. D. R., De Beer, M., Mellet, D. J., Maphike, H.S., and Foit, W. South
African Journal of Botany. 2007. 73: 600-605.
[37]-Vargas, M. A. T., Mendes, I. C., Suhet, A. R., and Peres, J. R. R. Revista-de Microbiologia.
1994. 25(4): 245-250.
[38]-Vollmann, J., Walter, H., and Schweiger, P. Computers and Electronics in Agriculture.
2011. 75: 190-195.
[39]-Wang, Q., Chen, J., Stamps, R. H., and Li, Y. Journal of Plant Nutrition. 2005. 28 (7):
1215-1225.
[40]-Wiersma, J. V. Agron J. 2005. 97: 924-934.
[41]-Yamamato, A., Nakamura, T., Adu-Gyamfi, J. J., and Saigusa, M. Journal of Plant
Nutrition. 2002. 25 (10): 2295-2301.
[42]-Zhang, S., Wang, Y., and Yang, Z. Soils and Fertilizers. Henan Acad. Agril. Sci. Henan,
China, 1996. 3: 37-39.
422
Scholars Research Library