International Research Journal of Plant Science (ISSN: 2141-5447) Vol. 2(5) pp. 137-142, May, 2011
Available online http://www.interesjournals.org/IRJPS
Copyright © 2011 International Research Journals
Full length Research Paper
Plant population influence on the physiological indices
of Wheat (Triticum aestivum L.) cultivars
Raouf Seyed Sharifi1, Hasan Bigonah Hamlabad 2, Jafar Azimi2
1- College of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran
2- Islamic Azad University , Ardabil Branch, Ardabil, Iran.
Accepted 24 May, 2011
In order to evaluation of effects of different plant population levels on yield and growth indices of wheat
(Triticum aestivum L.) cultivars, a factorial experiment based on randomized complete block design was
conducted in Research Farm Islamic Azad University, Ardabil branch in 2006. Factors were: plant
population levels at three levels (400, 450 and 500 seedsm-2) and wheat cultivars at four levels (Azar,
Sardari, Frankia and Trakia). The results showed that various levels of plant population affected yield and
growth indices of wheat (Triticum aestivum L.). Mean comparison in compound of treatment cultivar×
levels of plant population showed that maximum grain yield was obtained by the plots which was applied
-2
500 seed m with Azar cultivar. Investigation of variances trend of total dry matter indicated that in all of
treatment compounds, it increased slowly until 172 days after sowing with increasing of plant population
and then increased rapidly till 284 days after sowing. From 284 days after sowing till harvest time, it
decreased due to increasing aging of leaves and decreasing of leaf area index. Increase in plant
population levels also significantly increased the crop growth rate and the maximum of it was observed
-2
by the plots that was applied 500 seed m with Azar cultivar. In addition, in all of treatment compounds,
CGR increased slowly until 228 days after sowing and then decreased till 298 days after sowing due to
increasing aging of leaves and decreasing of leaf area index. Thus, it can be suggested that in order to
increasing of grain yield, total dry matter, crop growth rate and the other of physiological indices should
be applied Azar cultivar with 500 seed m-2 in conditions of Ardabil Plain.
Key words: wheat, population density, physiological indices
INTRODUCTION
Wheat (Triticum aestivum L.) is one of the most
important grain crops in the world. The yield of wheat in
Iran is very low as compared to other wheat producing
countries. One of the most important effective factors is
non application of optimal plant population per hectare
and wheat genotypes differ in their response to plant
density. In the other hand, plant density is one of the
major factors determining the ability of the crop to
capture resources. It is of particular importance in wheat
production because it is under the farmer's control in
most cropping systems (Satorre, 1999). Optimum plant
density varies greatly between areas according to
climatic conditions, soil, sowing time and varieties (Gate
1995). Consequently, there is value in defining
*Corresponding author Email: Raouf_ssharifi@Yahoo.com, Tel:
0098-914-3556585,Fax: 00984515512204
relationships between density and wheat yield to
establish optimum seeding rates for various regions
(Puckridge and Donald 1967; Faris and De Pauw 1981;
Frederick and Marshall 1985; Joseph et al 1985; Blue et
al 1990; Anderson et al 1991; Campbell et al 1991;
Douglas et al 1994; Qi-Yuan et al 1994; Anderson and
Sawkins 1997). The physiological indices such as leaf
area index (LAI), total dry matter (TDM), crop growth rate
(CGR) and relative growth rate (RGR) are influenced by
genotypes, plant population, climate and soil fertility
(Murphy et al 1996). Weber et al (1966) reported that
both total dry matter and leaf area index were poor
predictors of grain yield. Dry matter production of crops
needs on the amount of intercepting solar radiation and
its conversion to chemical energy. When plant density is
too high, it encourage inter plants competition for
resources. Then crop net photosynthesis process will be
affected due to less light penetration in
138 Int. Res. J. Plant Sci.
the crop canopy as well as increase in the competition
for available nutrient which will affect grain yield. On the
other hand, application of optimum plant density helps for
the proper utilization of solar radiation. Rao et al (2002)
suggested that leaf area index (LAI) and leaves
architecture are two main characteristics that define light
interception in the canopy. Plant population modifies the
canopy structure and influenced light interception, dry
matter production and yield crop (Fukai et al 1990). Total
dry matter is influenced by relative growth rate, crop
growth rate and net assimilation rate (Egly and Guffy
1997). Crop growth rate is directly related to the amount
of radiation intercepted by the crop (Jeffrey et al 2005).
Dwyer et al (1999) reported that increasing in population
plant decreased leaf area index and net assimilation rate
(NAR) per plant, but increased them in per area. Past
research showed a variation in the responses of different
wheat varieties to density (Faris and De Pauw 1981;
Gate 1995; Couvreur et al 1999; Wiersma 2002).
Varieties have different abilities or plastic ties to
compensate for low or high plant populations by
modifying the number of tillers and consequently the
number of spikes per square meter, the number of
kernels per spike, or the grain weight. The objective of
this study was to obtain the best population density and
cultivar of wheat for obtaining maximum of grain yield
and growth indices such as leaf area index, total dry
matter and crop growth rate in conditions of Ardabil
Plain in Iran.
MATERIALS
A factorial experiment based on randomized complete
block design with three replications was conducted in
2006 at the Research Farm of Islamic Azad University,
Ardabili Branch in Iran (lat 38 ْ◌ 15΄ N; long 48 ْ◌ 30΄ E;
Alt 1350 m). Climatically, the area placed in the semiarid temperate zone with cold winter and hot summer.
Average rainfall was low than 340 mm that most rainfall
concentrated between winter and spring. The soil was
loam silty with pH about 8.2. Mean temperatures and
rainfall for the 2006 wheat growing season is given in
Figure 1.
Before sowing of the crop the field was well prepared
by plowing twice with tractor followed planking to make
a fine seed bed. Treatments were three densities
-2
containing, 400 (D1), 450 (D2) and 500 seedsm (D3)
plus wheat cultivars (Azar, Sardari, Frankia and Trakia).
The inter-row spacing was 20 cm. Plot size was 6 m ×1
m with five rows per plot. Plots and blocks were
separated by .5 m unplanted distances. The area was
mold board-ploughed and disked before planting. Wheat
seeds were planted in the first week of October. All
other agronomic operations except those under study
were kept normal and uniform for all treatments.
Harvest sample was taken of 3 m long from the three
middle rows for measuring grain yield. For estimation of
growth analysis, eight plants were sampled randomly in
each treatments and average for recording the change
in dry weight in shoots (above ground), interval at
different stages of the wheat growth was 14 days. The
first sampling was 117 days after sowing. For dry weight
determination, samples were oven dried at 70 ‫ه‬C to
constant weight. Leaf area index was determined by
dividing leaf area over ground area. The variances trend
of total dry matter (TDM), crop growth rate (CGR) and
relative growth rate (RGR) was determined with using of
equations Acuqaah (2002); Gupta and Gupta (2005).
Analysis of variance was performed using SAS
computer software packages.
RESULTS AND DISCUSSION
Study of trend of variances total dry matter in treatment
compounds wheat cultivars × various levels of plant
population (Table 1) showed that in all of cultivars, total
dry matter increased during plant growth with increasing
plant population and reached to a maximum level at
270-284 days after planting, then showed a declining
trend at maturity (284-299 DAS). Similar results were
also reported by Egly and Guffy (1997). The increase in
total dry matter with the increasing of plant population
indicates the favorable response of wheat cultivars to
plant population. It is perhaps related to accelerating the
photosynthesis activity that is caused dry matter
accumulation increased. Study of total dry matter trends
of Azar cultivar in various levels of plant population
shows that dry matter increased slowly until 172 days
after sowing and then increased rapidly till 172-284
days after sowing. From 284 days after sowing till
harvest time, accumulated dry matter decreased due to
increasing aging of leaves, decreasing of leaf area
index (Table 1 and 4). On the other hand, total dry
matter in unit of area increased with increasing levels of
plant population, as the maximum and the minimum
biomass in unit of area obtained from 400 and 450
seeds m2, respectively (Table 1). Study the total dry
matter in other cultivars (Sardari, Frankia and Trakia)
indicated that in all of cultivars increased with increasing
of plant population (Table 1) and trend of variances
were similar to dry matter acumulation in Azar cultivar.
Crop growth rate
Study of trend of variances crop growth rate showed
that in all of cultivars, the crop growth rate was low in
the beginning of sampling, increased thereafter
considerably up to 228 days after planting with a peak
during 218 days after planting (table 2), then showed a
declining trend at 218-298 days after planting. The
increase in CGR with the increasing rate of plant
Sharifi et al. 139
50
40
30
20
10
0
Oct
Nov
Dec
Jan
Feb
March April
May
June
July
-10
Tmin(0 c)
Tmax(0 c)
Rainfall (mm)
Figure 1. Minimum and maximum temperature and rainfall recorded during the period of
wheat growth (Septamber –June) in 2006-2007
Table 1. Plant population influence on variances trend of total dry matter (TDM) in wheat cultivars
Days after planting
Treatment
compounds
-2
Azar × 400 seeds m
-2
Azar × 450 seeds m
-2
Azar × 500 seeds m
-2
Sardari× 400 seeds m
Sardari× 450 seeds m
Sardari× 500 seeds m
-2
Trakia × 400 seeds m
Trakia × 450 seeds m
Trakia × 500 seeds m
Frankia × 400 seeds m
Frankia × 450 seeds m
Frankia × 500 seeds m
0-172
22.9
24.5
26
20
22.5
24
20
22
23.5
20.5
21.4
22.5
173186
56
60
65
48
52
58
46
49
52
45.2
49.5
53
187200
110
119
123
97.5
105.6
118
90
95
102.3
105
109
113
201214
184
193.5
205
159
172
186.9
153
160
168
172
178
192
215228
258
276.5
284
229
243
271
216
229
243.8
248
260
272
229242
330
349.9
368
290
309.8
342.5
276
289
308
313
328
350
243256
382
413
430
341
362
402
318
335
362
365
380
410
257270
416
448.9
466.5
368
392
436
349
368
392
400
408
446
271284
446.5
483
499
396
419
473.5
366
392
422
430
446
472
285298
433
469
485
383
411.5
459
368
380
409
416
432
460
Table 2. Plant population influence on variances trend of crop growth rate (CGR) in wheat cultivars
Days after planting
Treatment
compounds
0-172
Azar × 400 seeds m-2
-2
Azar × 450 seeds m
Azar × 500 seeds m-2
-2
Sardari× 400 seeds m
Sardari× 450 seeds m
Sardari× 500 seeds m
Trakia × 400 seeds m-2
Trakia × 450 seeds m
Trakia × 500 seeds m
Frankia × 400 seeds m
Frankia × 450 seeds m
Frankia × 500 seeds m
1.64
1.7
1.83
1.56
1.61
1.73
1.37
1.45
1.78
1.33
1.44
1.53
173186
3.11
3.24
3.73
2.98
3.08
3.3
2.6
2.76
3.39
2.53
2.74
2.91
187200
4.7
4.89
5.63
4.51
4.66
4.98
3.93
4.17
5.13
3.8
4.15
4.4
201214
5.3
5.97
6
5.51
5.19
5.49
4.28
4.39
4.56
4
4.76
4.87
population may be due to the positive response of
wheat to plant population. Similar results were also
215228
5.74
5.97
6.87
5.52
5.7
6.1
4.66
4.73
4.88
4.67
5.06
5.37
229242
4.73
4.93
5.68
4.57
4.72
5.05
3.96
3.41
3.17
3.86
4.18
4.43
243256
3.24
3.37
3.88
3.13
3.23
3.46
2.71
2.88
2.94
2.64
2.86
3.03
257270
1.87
1.94
2.23
1.805
1.86
1.99
1.5
1.65
2.13
1.52
1.64
1.74
271284
1.06
1.104
1.27
1.35
1.026
1.06
1.02
1.11
1.41
.86
.93
.99
285298
.87
.95
1
.7
.4
.35
.8
.7
.65
.8
.9
.94
reported by Jeffrey et al (2005). The decrease in crop
growth rate towards maturity is due to senescence of
140 Int. Res. J. Plant Sci.
Table 3. Plant population influence on variances trend of relative growth rate (RGR) in wheat cultivars
Days after planting
Treatment
compounds
0-172
Azar × 400 seeds m
-2
Azar × 450 seeds m
-2
Azar × 500 seeds m
Sardari× 400 seeds m
.0708
.077
.081
.07
173186
.055
.061
.064
.055
Sardari× 450 seeds m
Sardari× 500 seeds m
-2
Trakia × 400 seeds m
Trakia × 450 seeds m
Trakia × 500 seeds m
Frankia × 400 seeds m
Frankia × 450 seeds
m
Frankia × 500 seeds
m
.07
.08
.06
.067
.077
0.055
.061
.073
.055
.061
.073
0.0511
.044
.05
.042
.046
.055
0.0390
.034
.0409
.0131
.034
.0409
0.012
.0236
.028
.0215
.0236
.028
0.0199
.0152
.0183
.0139
.0152
.0183
0.0129
.0089
.0107
.0081
.0089
.0107
0.0075
.0047
.0056
.0043
.0047
.0057
0.0039
.0025
.0031
.0023
.0025
.0031
0.0021
.0021
.0026
.002
.0022
.0027
0.0018
0.06
0.056
0.042
0.03
0.021
0.014
0.008
0.004
0.002
0.002
0.07
0.067
0.051
0.03
0.026
0.017
0.009
0.005
0.002
0.002
-2
2
187200
.042
.0466
.048
.042
201214
.0131
.034
.0356
.031
215228
.0215
.023
.024
.021
229242
.0139
.0152
.0159
.0139
243256
.0081
.0089
.0093
.0081
257270
.0043
.00453
.00496
.00432
271284
.0023
.00258
.0027
.0023
285298
.002
.0024
.002
.002
Table 4. Plant population influence on variances trend of leaf area index (LAI) in wheat cultivars
Days after planting
Treatment
compounds
0-172
Azar × 400 seeds m
-2
Azar × 450 seeds m
-2
Azar × 500 seeds m
Sardari× 400 seeds m
.076
.07
.06
.068
173186
.18
.2
.28
.15
Sardari× 450 seeds m
Sardari× 500 seeds m
Trakia × 400 seeds m
.072
.078
.05
.18
.273
.168
.47
.604
.35
.906
1.129
.706
1.32
1.6
1.14
1.5
1.84
1.28
1.36
1.75
1.18
1
1.3
.85
.6
.67
.45
.3
.35
.25
Trakia × 450 seeds m
Trakia × 500 seeds m
Frankia × 400 seeds
m
Frankia × 450 seeds
m
Frankia × 500 seeds
m
.054
.059
.03
.18
.23
.1
.46
.55
.47
.85
.95
1
1.28
1.36
1.4
1.36
1.5
1.63
1.26
1.39
1.39
.95
1
.91
.5
.62
.57
.3
.35
.18
.085
.17
.7
1.2
1.8
1.93
1.68
1.16
.7
.4
.089
.24
.88
1.45
1.96
2.3
2.03
1.46
.94
.5
-2
2
2
187200
.43
.54
.68
.36
201214
.85
1.04
1.26
.705
215228
1.15
1.48
1.72
1.029
229242
1.4
1.72
1.96
1.28
243256
1.17
1.6
1.94
1
257270
.89
1.13
1.44
.7
271284
.48
.65
.83
.38
285298
.214
.276
.4
.15
lower leaves and decrease of leaf area index (Table 4).
Similar results were reported by Egly and Guffy (1997).
Relative growth rate
In the initial stages of the plant growth the ratio between
alive and dead tissues is high and almost the entire
cells of productive organs are activity engaged in
vegetative matter production. In conclusion, the relative
growth rate of plant crops is high. In all of treatment
compounds, RGR decreased during plant growth with
decreasing plant population and reached to a minimum
level at 284-298 days after planting. The reason of
decreasing in RGR at the final stage can be related to
increasing of the dead and woody tissues comparing to
the alive and active texture. Similar observations have
been reported by Jeffrey et al (2005).
Leaf area index
Leaf area index increased during plant growth with
increasing plant population and reached to a maximum
level at 228-242 days after planting. From 242 days
after sowing, leaf area index decreased due to
Sharifi et al. 141
a
159
b
b
b
158
c
grain yield (gr/m2)
grain yield (gr/m2)
160
140
160
a
180
120
100
80
60
40
20
157
156
155
c
154
153
152
0
151
400
450
500
azar
plant population (seeds per m2)
Grain yield
Grain yield is the main target of crop production. The
grain yield was significantly affected by both wheat
cultivars and plant density. Plant density significantly
increased the grain yield. The grain yield varied
2
-2
between 122.68 gr/m in 400 seeds m and 167.51
2
-2
gr/m in 500 seeds m (fig 2). The grain yield was
different in wheat cultivars. The grain yield varied
2
2
between 159.6 gr/m Azar cultivar and 154.3 gr/m in
Frankia cultivar (fig 3). Our findings are in agreement
with observations made by many researchers (Faris and
De Pauw 1981; Wiersma 2002). These results are in
agreement with total dry matter. This might be related to
correlation between grain yields with total dry matter.
Weber et al (1966) reported that both total dry matter
and leaf area index were poor predictors of grain yield.
frankia
trakia
w heat cultivars
Figure 2 . Means of comparison the effect plant density on grain yield
cultivars on grain yield
increasing aging of leaves, shading and competition
between plants for light and other resources.
Photosynthetic efficiency and growth in the crop plants
are strongly related to the effect of canopy architecture
on the vertical distribution of light within the canopy
(Williams et al 1968). Increasing leaf area index is one
of the ways of increasing the capture of solar radiation
within the canopy and production of dry matter. Hence,
the efficiency of the conversion of intercepted solar
radiation in to dry matter decreases with decreasing of
leaf area index. In the present study, trend of variances
leaf area index in treatment compounds of wheat
cultivars× various levels of plant population
was
according to crop growth rate. These results are in
agreement with trend of variances total dry matter.
Similar results have also been reported by Faris and
De Pauw (1981); Gate (1995); Couvreur et al (1999)
and Wiersma (2002).
sardari
Figure 3. Means of comparisons the effect wheat
CONCLUSION
In this experiment, plant population showed significant
effects on wheat cultivars yield, and physiological
indices of wheat such as total dry matter, crop growth
rate, relative growth rate and leaf area index. The
highest grain yield and physiological indices of wheat
-2
cultivars recorded in application of 500 seeds m with
Azar cultivar. In conclusion, it can be suggested that
Azar cultivar should be applied to 500 seeds m-2 in
conditions of Ardabil Plain.
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