American Journal of Plant Sciences, 2011, 2, 790-807
doi:10.4236/ajps.2011.26094 Published Online December 2011 (http://www.SciRP.org/journal/ajps)
Copyright © 2011 SciRes. AJPS
Interactive Effects of Drought Stress and
Phytohormones or Polyamines on Growth and
Yield of Two M (Zea maize L.) Genotypes
M. A. K. Shaddad1, M. Hamdia Abd El-Samad2, H. T. Mohammed1
1Botany Department, Faculty of Science, Assiut University, Assiut, Egypt, 2Department of Botany and Microbiology, Faculty of
Science, Minia University, Minia, Egypt.
Email: hamdia10@yahoo.com
Received November 19th, 2010; revised June 25th, 2011; accepted July 8th, 2011.
ABSTRACT
Two maize genotypes (Nefertiti and Bashaier) were picked up from nine maize genotypes during the early vegetative
growth (25 days) to be cultivated in open field upon the crop yield under the different drought stress levels (90,70,50,30)
or under the interaction effect of drought stress and phytohormones or polyamines. According to the data of growth
criteria, the maize genotype Nefertiti was found to be the most drought sensitive genotype, while the genotype Bashaier
was found to be the most drought resistant genotype. Additionally while the photosynthetic pigments remained more or
less unchanged in genotype Bashaier, their biosynthesis destroyed earlier in the drought sensitive genotype (Nefertiti).
Also while the genotype Bashaier absorbed and accumulated a sufficient amount of mono and divalent cations (K+,
Ca++ and Mg++), the genotype Nefertiti did not. Accordingly while the genotype Bashaier gave a crop yield up to 50%
field capacity, the genotype Nefertiti gave a crop yield only up to 70% field capacity and failed to give a crop yield be-
yond this level. The interaction effect of drought stress and phytohormones and polyamines improved the all above
characteristics. Interestingly each of these activators considerably improved the production of crop yield only in geno-
type Bashaier specially polyamines they produced more than 60% field capacity and at the level of 30% field capacity
(the level which did not give crop yield in this genotype). However, phytohormones in generally did not make an im-
portant effect on the crop yield in genotype Nefertiti although they improved the dry matter production during the ve-
getative stages. Such situation seemed to be complicated and borne many questions to be studied in the future.
Keywords: Drought, Maize (Zea maize L.), Phytohormones, Poly ami nes, Leaf Area, Dry Weight, Yield
1. Introduction
Drought is the most important limiting factor for crop
production and it is becoming an increasingly severe pro-
blem in many regions of the world [1,2]. Drought is still
a serious agronomic problem and one of the most impor-
tant factors contributing to crop yield loss. According to
statistics, the percentage of drought affected land areas
more than doubled from the 1970s to the early 2000s in
the world [3]. Maize is one of the major summer crops in
the irrigated areas of Egypt. However, maize is very sen-
sitive to water stress [4-6]. The effects of water stress on
maize include the visible symptoms of reduced growth,
delayed maturity and reduced biomass and crop grain
yield. For example, water stress on maize has been shown
to reduce plant height [6], leaf area index [7] and root
growth [8]. Grain yield can be reduced by decreasing yield
components like grain number and grain weight [5,9].
Many researchers have evaluated the effect of timing of
water stress on maize yield [6,10-12]. Flowering has been
found to be the most sensitive stage to water deficit, with
reductions in biomass, yield and harvest index [4,5,9,13,
14]. The high sensitivity of maize to water stress means
that under water limiting conditions it is difficult to im-
plement irrigation management strategies without incur-
ring significant yield losses [4,15]. Much of the past re-
search on water stress on maize has consisted of full
withholding of irrigation and conditions of severe water
stress [11,12]. It is clear from the literature that cessation
of irrigation in maize causes significant yield losses.
Therefore, it is important to know the crop response to
moderate water deficit at different growth stages and un-
der cropping and irrigation conditions similar to the one
experienced by farmers in the area.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
791
Phytohormones such as IAA, gibberellic acid (GA3),
and kinetin are known to be involved in the regulation of
plant response to the adverse effect of stress conditions
[16-18] show that plant hormones can be defined as or-
ganic substances that are produced in one part of plant
and trans located to another parts, where at very low con-
centration, they stimulate physiological response. Plants
are usually subjected to environmental factors such as
drought or water salinity.
Also, exogenously applied phytohormones or poly-
amines have multiple roles in improving drought tole-
rance of maize. These functions are improved cell water
status and alleviation of oxidative damage on the bio-
logical membranes. This suggests that maintenance of
water economy through stabilized cellular structure is an
important mechanism of drought tolerance in maize. Es-
tablishment of similar roles of polyamines are likely to
be a great step in improving drought tolerance in high
water requiring plant species.
Polyamines are now being regarded as plant growth
regulators and secondary messenger in signaling path-
ways [19-21], and play an array of physiological roles in
plant growth and development [22]. Although, they in-
duce tolerance against several abiotic stresses in plants
[23-25], mechanisms of their action during exogenous
application in modulating physiological phenomena and
improving drought stress tolerance are not fully under-
stood.). Thus the aim of the present work was to test the
effect of exogenous treatments with some phytohor-
mones and polyamines in counteracting the adverse ef-
fects of drought on growth, photosynthetic pigments,
some mineral contents and yield production, of the two
maize genotypes, which has been recorded to be differed
in their drought stress tolerance according to the data of
short duration experiment [26].
2. Materials and Methods
A field experiment was conducted using two maize ge-
notypes Bashaier and Nefartiti selected for drought tole-
rance in the growth chamber experiments. Grains were
obtained from the breeding program of seeds station,
Beni-suef, Egypt to be used in the field Work of Minia
governorate. In view of the nature of the field experiment,
Minia represented an ideal location since it is virtually
rainless in the summer. A randomized split plot design
was used [27]. Soil plots (50 m2) were prepared by add-
ing manure 25 m3 Feddan-1 (60 m3·ha–1), plowing twice
(once perpendicular to the other), leveling, and lining (7
m-long lines, 60 cm apart). Sowing (early June) on lines
in small holes (Goras, 25 - 30 cm apart, two seeds per
hole). Only one seedling per Gora was left after seedling
establishment. Fertilizers included 200 kg. Feddan–1 Su-
perphosphate (15% P2O5), and 120 units nitrogen Fed-
dan–1 (200 kg Feddan-1 46% urea, in three installments
once after sowing, once after second irrigation, and once
after third irrigation). Plots were flood-irrigated after sow-
ing, and seeds were sown in each plot and soil was
brought to field capacity, then plots are classified into four
groups according to the amount of moisture content in
each plot. Plants were grown with further irrigation at
90%, 70%, 50%, and 30% field capacity, plants was ir-
rigated every 12 day with these field capacities. Irriga-
tion water was thoroughly measured by introducing a
water meter on the irrigation line. Irrigation was stopped
three weeks before harvest to allow drying. Plants were
harvested 120 days after sowing.
Plants in each soil plots are classified into eight groups
the first group was the control, the rest groups were
treated with 10 ml 200 μ. mol of one of the polyamines
(putrescine, spermine or mixture of putrescine and sper-
mine polyamines) or 20 μ. mol of one of the phytohor-
mones (IAA, GA3, Kinetin and mixture of these phyto-
hormones). Plants are treated with these phytohormones
or polyamines two time during the age of maize the first
at 30 old-days and the second at 45 old-day. At the end
of the experimental period plant height, dry matter yield
of the different organs (stem and leaves) were deter-
mined. Plant height was determined by direct measure-
ment from soil surface to the tip of the flag leaf. Deter-
mination of the dry matter involved harvesting and care-
ful separation of fresh organs. Fresh organs were then
dried in an oven at 80˚C. Successive weighing was car-
ried out until a constant dry weight was recorded. Leaf
area was determined by measuring leaf length and maxi-
mum width and applying the formula;
Leaf area = k (leaf length * leaf maximum width)
cm2·plant–1
This formula provided a simple way for determination
of leaf area particularly in the field where large leaves
had to be measured. The coefficient k was calculated and
assigned different values for different grasses [28,29],
and was recently reviewed and given a value of 0.75 for
maize [30]. The photosynthetic pigments, chlorophyll a,
chlorophyll b and carotenoids, were determined using the
spectrophotometric method recommended by [31]. The
flame emission technique was chosen for determination
of potassium due to its simplicity, precision, and sensi-
tivity. A flame photometer (Corning 410, Corning Sci-
ence Products, Halstead, Essex, England) was used for
this purpose.
The EDTA titration method was employed for calcium
and magnesium of different plant organs [32]. Harvest
was carried out 120 days after sowing and cobs were left
to dry (air dry for 2 weeks). Yield was determined as
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
792
Ardab Feddan–1 (Ardab = 120 kg) of air-dry grains. Yield
attributes determined included the 1000 grain weight,
and number of grains in each row.
3. Statistical Analysis
The experimental data were subjected to the one way
analysis of variances (ANOVA test) using the SPSS ver-
sion 11.0 to quantify and evaluate the source of variation
and the means were separated by the least significant
differences, L.S.D. at P level of 0.05% and 0.01% [33].
4. Results
The data in Table 1 reveal that, the dry weight of stem
and leaves of maize genotype Nefertiti decreased highly
significantly by increasing the drought stress level in the
soil. This reduction in the dry weight of stem and leaves
was highly significant even at the highest soil moisture
content level used when compared with the relative con-
trol values (90% F.C.). At the level of 30% F.C the per-
cent of reduction in the dry weight in stem and leaves
was 75%, and 62% respectively, which indicate more
deleterious effect of sever drought stress was recorded in
dry weight of maize genotype Nefertiti. The stimulatory
effect of the growth promoters varied considerably from
one to another. Polyamines alone or in combination in-
crease the dry matter yield at 50% F.C over those of the
relative control values, (the level which reduce dry mat-
ter yield to about 50% in only drought stresses plants).
Also IAA promoted the dry matter production in plants
irrigated with 50% F.C by about 56% over those of re-
lated control value. Kinetine and mixture phytohormones
induce a slight increase in these values at 50% F.C
(about 27%). GA3 alleviated the inhibitory effect of
drought at 50% F.C. In general polyamines seemed to be
the superior up to 50% F.C, while phytohormones were
the superior at 30% F.C (most of them nearly alleviated
the inhibitory effect of drought stress.
Drought stress up to 70% F.C induced a slight effect in
the stem dry weight of maize genotype Bashaier, then it
reduced gradually by the further increase in the level of
drought stress. On the other hand the dry matter yield of
leaves remained more or less unchanged up to the level
of 50% F.C, and then a minute reduction was obtained.
At the level of 30% F.C the percent of reduction in the
dry weight of stem and leaves was 51% and 20% respec-
tively in compared with the relative control (90% F.C).
Phytohormones or polyamines treatments considerably
increased the values of dry weight of stem and leaves of
maize genotype Bashaier as compared with those of
plants subjected only to the various level of drought
stress. According to the data of dry matter of stem and
leaves the maize genotype Bashaie r considered the drought
tolerant genotype, while the maize genotype Ne- fertiti
was the drought sensitive genotype. At the level of 30%
F.C, the percent of reduction in the stem dry weight in
maize genotype. Bashaier was 51% while in maize ge-
notype Nefertiti the percent of reduction in the stem dry
weight was 75%. Thus the data of field experiment rec-
ommended the data of growth chamber experiment where
maize genotype Ba shaier still the most drought tolerant
genotype and the maize genotype Nefertiti was the most
drought sensitive genotype.
The leaf area of the maize genotype Nefertiti decreased
highly significant by decreasing the soil moisture content,
this reduction was more pronounced at the lowest field
capacity used (30% F.C). At this level the percent of
reduction was about 45% as compared with the relative
control. The inhibitory effect of drought stress on the
values of leaf area was completely alleviated as a result
of phytohormones and polyamines treatments.
Spermine was the most effective in the production of
leaf area especially at the level of 90% F.C when com-
pared with putrescine. The mixture of putrescine & spe-
rmine was much more obvious in production of leaf area
at all soil moisture content used. It is worthy to mention
that, the highest values of leaf area obtained at the level
of 30% F.C were recorded in plants treated with IAA or
the mixture of polyamines (Ta ble 2).
The leaf area of maize genotype Bashaier decreased
smoothly by increasing the drought stress level in the soil.
It reduced by only 24% at the level of 30% F.C. Phyto-
hormones treatment considerably increased the values of
leaf area, whatever the level of the soil moisture content
used as compared with the corresponding drought stressed
plants. Interestingly kinetin seemed to be the most effec-
tive phytohormones in the two maize cultivars at the
sever drought than the other phytohormones and or the
mixture of them. Also, while IAA was the least effective
phytohormones at mild drought it on the other hand the
most effective at sever drought stress. Polyamines treat-
ment resulted in a considerable increase in these values
over those of the relative control up to the level of 70%,
which was much more obvious in plants sprayed with
mixture of polyamines. Thereafter these polyamines con-
siderably elevated the values of leaf area, when com-
pared with those of plants subjected to the 50% and 30%
F.C without polyamines treatment (Table 2).
One of the especial interest in this work is that the
number of leaves remained constant in the two maize
genotypes Nefer titi, and Bashaier whatever the treatment
used which means that, the differences might located in
the growth of leaves (area), rather than in the number of
leaves which means that at least in maize external envi-
ronmental conditions is not a limiting factor in the num-
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
793
Table 1. Interactive effect of drought stress and phytohormones or polyamines on dry matter of stem and leaves (gm·plant–1)
of two t he maize genotypes.
Bashaier (drought tolerant) Nefertiti (drought sensitive)
% Leaves D·wt % stem D·wt % Leaves D·wt % Stem D·wt
F.C Tr eat m ent s
100 30 100 87 100 29 100 59 90%
97 29 98 85* 76 22** 86 51** 70%
93 28* 89 77** 62 18** 56 33** 50%
80 24** 49 43** 38 11** 25 15** 30%
Control
153 46** 178 155** 86 25** 151 89** 90%
130 39** 155 135** 131 38** 215 127** 70%
107 32* 131 114** 103 30 156 92** 50%
107 32* 85 74** 90 26** 83 49** 30%
IAA
127 38** 159 138** 96 28 153 90** 90%
133 40** 134 117** 134 39** 186 110** 70%
113 34** 99 86 110 32** 105 62 50%
96 29 89 78* 82 24** 76 45** 30%
GA3
143 43** 144 125** 134 39** 192 113** 90%
133 40** 132 115** 134 39** 181 107** 70%
130 39** 108 94* 120 35** 127 75** 50%
93 28* 86 75** 103 30 80 47** 30%
Kinetin
140 42** 160 139** 138 40** 220 130** 90%
130 39** 142 124** 134 39** 203 120** 70%
127 38** 113 98** 110 32** 129 76** 50%
86 26** 84 73** 75 22** 81 48** 30%
Mixture
hormone
160 48** 159 138** 120 35** 231 136** 90%
133 40** 149 130** 117 34** 180 106** 70%
113 34** 114 99** 113 33** 144 85** 50%
100 30 80 70** 75 22** 63 37** 30%
Putrescine
156 47** 160 139** 137 40** 217 128** 90%
153 46** 131 114** 96 28 147 87** 70%
113 34** 115 100** 86 25** 117 69** 50%
90 27** 86 75** 79 23** 59 35** 30%
Spermine
160 48** 163 142** 155 45** 225 133** 90%
126 38** 149 130** 131 38** 190 112** 70%
133 40** 121 105** 113 33** 153 90** 50%
96 29 83 72** 89 26** 66 39** 30%
Mixture poly
amines
2.38 2.55 2.24 7.16 0.01
1.79 1.92 1.68 5.39 0.05
LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
794
Table 2. Interactive effect of drought stress and phytohormones or polyamines on number of leaves per plant , and leaves area
(cm2·plant–1) of two maize genotypes.
Bashaier (drought tolerant genotype) Nefertiti (drought sensitive genotype) F.C Tr eat m ent s
% Leaf area % No, of leaves % Leaf area % No, of leaves
100 6150 100 15 100 4637 100 15 90%
90 5546** 100 15 82 3802** 100 15 70%
84 5151** 93 14 58 2700** 100 15 50%
76 4700** 87 13* 55 2570** 87 13* 30%
Control
104 6425** 107 16 91 2400** 93 14 90%
102 6306** 107 16 130 6036 ** 93 14 70%
91 5605** 100 15 101 4685 93 14 50%
89 5473** 100 15 80 3700** 93 14 30%
IAA
113 6937** 100 15 103 4776 ** 93 14 90%
107 6583** 100 15 136 6300 ** 93 14 70%
83 5103** 100 15 108 5 000 ** 80 12** 50%
75 4628** 93 14 65 3000** 73 11** 30%
GA3
114 7000** 107 16 104 4800 ** 107 16 90%
113 6975** 107 16 83 3829** 100 15 70%
98 6003** 100 15 80 3700** 100 15 50%
82 5020** 93 14 71 3280** 87 13* 30%
Kinetin
111 6859** 100 15 132 6100 ** 107 16 90%
110 6762** 100 15 129 6000 ** 100 15 70%
88 5430** 100 15 111 5 140 ** 87 13* 50%
67 4140** 93 14 75 3475** 73 11** 30%
Mixture
hormone
108 6660** 107 16 107 4961 ** 100 15 90%
101 6236** 107 16 93 4300** 100 15 70%
84 5165** 107 16 88 4100** 93 14 50%
83 5082** 100 15 57 2630** 60 9** 30%
Putrescine
109 6730** 107 16 137 6373 ** 107 16 90%
106 6519** 107 16 91 4200** 107 16 70%
96 5918** 106 16 86 4000** 87 14 50%
86 5292** 100 15 66 3068** 73 11** 30%
Spermine
117 7214** 100 15 135 6304 ** 100 15 90%
111 6827** 100 15 136 6300 ** 100 15 70%
97 6000** 100 15 104 4 813 ** 100 15 50%
81 4960** 100 15 80 3700** 67 10** 30%
Mixture poly
amines
68.55 2.17 57.96 2.43 0.01
46.43 1.63 35.98 1.83 0.05 LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
795
ber of leaves.
The data of maize genotype Nefertiti in Table 3 reveal
that chlorophyll “a, b, and carotenoids” contents de-
creased by decreasing the soil moisture content, which
was much more obvious at the sever drought A marked
and progressive increase in the photosynthetic pigments
concentration was exhibited when the drought stressed
plants sprayed with phytohormones or polyamines, which
was much more obvious in IAA treated plants.
The data of maize genotype Bashaier in Table 4 ob-
served that, the photosynthetic pigments (chlorophyll “a,
b, and carotenoids) concentration remained almost more
or less unchanged at most drought stress level and a
slight reduction was recorded in these values only at the
level of 30% F.C. Using of the growth regulators (phy-
tohormones or polyamines) considerably activated the
biosynthesis of the photosynthetic pigments. This stimu-
latory effect was much more obvious in polyamines
treated plants than in phytohormones treated plants. Also,
the mixture of polyamines was the superior especially at
the sever drought when compared with the other activa-
tors.
The data of maize genotype Nefertiti in Table 5 re-
veals that, The contents of potassium in shoots and roots
slightly increased up to the level of 50% F.C, then it re-
mained more or less unchanged even at the lowest field
capacity used (30% F.C). A marked and progressive ac-
tivation in absorption of K+ in shoots and roots has been
observed as a result of phytohormones or polyamines
treatment. There is no, observable differences among the
different growth promoting substances used (Ta ble 5)
The data of maize genotype Nefertiti in Table 5 re-
veals that, there is a highly significant reduction in the
absorption and accumulation of Ca++ and Mg ++ in shoots
and roots, as the drought stress level increased in the soil
the highest reduction was obtained at the highest drought
stress level used. On the other hand the absorption and
accumulation of Ca++ and Mg++ improved as a result of
the interaction effect of phytohormones or polyamines in
shoots and roots of the maize genotype Nefertiti. This
stimulatory effect was more pronounced in shoots than in
roots and in polyamines treated plants than in phytohor-
mones treated plants.
The data of the maize genotype Bashaier in Table 6
reveals that, the contents of potassium in shoots and roots
increased progressively by increasing drought stress level
in the soil, therefore the highest increase in K+ content was
found to be at 30% F.C. At this level the percent of in-
crease in K+ content in shoots and roots was 124% and
128% respectively in relation to the relative control val-
ues. The amount of K+ in shoot was much higher than in
roots whatever the drought stress level used. Additional
activation in K+ content in shoots and roots of drought
stressed maize genotype Bashaier was observed as re-
sults of the phytohormones or polyamines treatments.
This seemed to be more observable in shoots than in
roots. The data of maize genotype Bashaier in Table 6
reveal that, there is a general promotion in the absorption
and accumulation of calcium and magnesium in stems
and roots of maize genotype Bashaier by drought stress.
This was more pronounced in roots than in stems.
Treatment with growth regulators resulted in most cases
in a general activation in calcium and magnesium in the
two tested plant organs.
The data of maize genotype Nefertiti in Table 7 re-
veals that, the number of grains per ear and the 1000
grain weight reduced slightly in up to the level of 70%
F.C. On the other hand the number of grains and the
1000 grain weight increased progressively at the level of
90% F.C, and to some extent at the level of 70% F.C as a
result of phytohormones or polyamines treatment
The data of maize genotype Nefertiti in Table 7 re-
veals that, it is worthy to mention that, the drought sensi-
tive cultivar produce crop yield only up to the level of
70% F.C, while treatment with polyamines produce crop
yield up to 50% F.C. The crop yield at the level of 50%
in plants treated with putrescine, spermine or mixture
polyamines was 13, 15, and 12.8 Ardab/feddan in rela-
tion to 21.14 Ardab/feddan produced in normally treated
plants (90% F.C). Also IAA is the only phytohormone
which produce crop yield at the level of 50% F.C (5.23
Ardab/feddan). Additionally all of the used polyamines
increased the crop yield at the normal condition (90%
F.C) as compared with untreated plants. The crop yield
of plants treated with putrescine, spermine or mixture
polyamines was 26.5, 24, and 26 Ardab/feddan com-
pared to 21.14 (at the normal level). Moreover plants
treated with mixture of polyamines produced 25 Ardab/
feddan; at the level of 70% F.C. GA3, Kinetin and mix-
ture of hormones retarded the crop yield even at the level
of 90% F.C, although they considerably enhance the
plant growth during the vegetative stage. This unex-
pected phenomenon seemed to be complicated and needs
a numerous and further studies, Why those phytohor-
mones stimulated the vegetative growth and inhibit crop
yield? Is there a negative correlation between the exoge-
nous application of these phytohormones and the group
of phytohormones responsible for the flowering and fruit-
ing or associated with the exogenous dose of the applied
phytohormones???,, Is a concentration affect,, or what????
The data of maize genotype Bashaier in Table 8 re-
veals that, imposing drought stress induce a very minute
reduction in a number of grains per ear (12% only at
50% F.C) and the 1000 grain weight. On the other hand
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
796
Table 3. Interactive effect of drought stress and phytohormones or polyamines on chlorophyll a, chlorophyll b, and carote-
noids (mg·gm–1 dwt) of maize cv. Nefertiti.
% Carotenes % Chlorophyll “b” % Chlorophyll “a” F.C Trea tments
100 2.67 100 5.49 100 12.44 90%
68 1.82** 90 4.96** 98 12.2* 70%
63 1.67** 80 4.33** 55 6.87** 50%
55 1.46** 78 4.31** 60 7.43** 30%
Control
86 2.3** 230 12.64 198 24.63** 90%
107 2.88** 229 12.62* 186 23.10** 70%
102 2.72 229 12.62* 197 24.54** 50%
130 3.49** 147 8.10** 191 23.76** 30%
IAA
51 1.36** 216 11.88** 124 15.38 90%
40 1.08** 222 12.17* 116 14.43** 70%
103 2.76** 172 9.44** 143 17.84** 50%
230 6.16** 87 4.76** 157 19.52** 30%
GA3
104 2.77** 233 12.78** 130 16.19** 90%
95 2.54** 181 9.91** 160 19.91** 70%
89 2.37** 133 7.28** 97 12.12** 50%
137 3.66** 131 7.2** 108 13.52** 30%
Kinetin
83 2.22** 224 12.28** 143 17.79** 90%
78 2.08** 209 11.51** 121 15.00** 70%
79 2.12** 163 8.96** 116 14.48** 50%
89 2.38** 143 7.88** 114 14.14** 30%
Mixture hormone
52 1.39** 316 17.34** 147 18.32** 90%
76 2.04** 276 15.15** 131 16.27** 70%
128 3.43** 190 10.43** 166 20.64** 50%
69 1.85** 185 10.17** 153 19.01** 30%
Putrescine
149 3.99** 191 10.49** 121 15.03** 90%
120 3.21** 183 10.03** 111 13.75** 70%
105 2.81** 160 8.8** 148 18.45** 50%
62 1.65** 150 8.26** 147 18.29** 30%
Spermine
80 2.14** 244 13.38** 107 13.28** 90%
82 2.2** 268 14.75** 118 14.65** 70%
168 4.5** 159 8.73** 102 12.69** 50%
100 2.69 152 8.35** 148 18.43** 30%
Mixture poly
amines
0.07 0.28 0.168 0.01
0.053 0.21 0.127 0.05 LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
797
Table 4. Interactive effect of drought stress and phytohormones or polyamines on chlorophyll a, chlorophyll b, and carote-
noids (mg·gm–1 dwt) of maize genotyp e Bashaier.
% Carotenes % Chlorophyll b % Chlorophyll a F.C Treatm ent s
100 3.86 100 9.37 100 15.62 90%
72 2.78** 87 7.24** 100 15.6 70%
71 2.74** 88 8.25** 80 12.49** 50%
70 2.69** 96 8.98* 73 11.48** 30%
Control
100 3.86 104 9.74* 150 23.49** 90%
42 1.64** 118 11.05** 136 21.24** 70%
107 4.14 136 12.78** 191 29.79** 50%
97 3.73 126 11.86** 142 22.64** 30%
IAA
36 1.38** 132 12.04** 149 23.27** 90%
138 5.32** 126 11.79** 136 21.26** 70%
82 3.18* 141 13.2** 117 18.20** 50%
88 3.39 108 10.12** 131 20.48** 30%
GA3
47 1.82** 148 13.86** 146 22.78** 90%
89 3.44 146 13.71* 142 22.17** 70%
87 3.37 138 12.92** 186 28.98** 50%
60 2.32** 136 12.90** 107 16.69** 30%
Kinetin
81 3.12** 89 8.36** 107 16.69** 90%
97 3.76 112 10.51** 142 22.19** 70%
111 4.32 139 13.07** 178 27.74** 50%
102 3.97 158 14.85** 181 28.25** 30%
Mixture hor-
mone
87 3.37 121 11.38** 105 16.43** 90%
88 3.38 141 13.23** 184 28.71** 70%
130 5.3** 144 13.47** 175 27.37** 50%
74 2.86** 174 16.3** 208 32.51** 30%
Putrescine
58 2.23** 120 11.23** 120 18.75** 90%
128 4.96** 172 16.08** 235 36.68** 70%
120 4.64** 130 12.18** 138 21.75** 50%
143 5.55** 146 13.68** 196 30.69** 30%
Spermine
138 5.35** 212 19.85** 124 19.36** 90%
197 7.64** 166 15.56** 213 33.33** 70%
131 5.06** 156 14.59** 167 26.06** 50%
169 6.53** 175 16.44** 218 34.07** 30%
Mixture poly
amines
0.69 0.50 0.078 0.01
0.52 0.37 0.059 0.05 LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
798
Table 5. Interactive effect of drought stress and phytohormones or polyamines on potassium, calcium and sodium (mg·gm–1
plant dwt) of maize genotype N efertiti.
K+ Ca++ Mg++
Treatm ent F.C Shoot % Root % Shoot % Root % Shoot % Root %
90% 11.1 100 10.4 10022 10018 1006.9 100 6.1 100
70% 11.9** 107 12.1** 116 21** 95 14** 78 6.1** 88 5.2** 85
50% 11.9** 107 13.6** 131 20** 91 13** 72 5.2** 75 4.2** 68
Control
30% 10.6** 95 9.9** 95 16** 73 10** 56 4.4** 64 4.1** 67
90% 14.8** 133 11.9** 114 28** 127 21** 117 10** 145 7** 115
70% 12.6** 113 14.8** 142 32** 145 22** 122 11** 159 8.4** 137
50% 10.6** 95 17.2** 165 26** 118 26** 144 8** 116 6 98
IAA
30% 10.6** 95 13.8** 133 24** 109 24** 133 8** 116 9.6** 157
90% 12** 108 16** 154 21** 95 26** 144 14.4** 209 8.2** 134
70% 17.5** 157 13.4** 129 23** 105 26** 144 14** 203 7.1** 116
50% 13.3** 119 15.2** 14622 10024** 133 13** 188 7.1** 116
GA3
30% 16.5** 148 15.5** 14922 10023** 128 11** 159 6.2 101
90% 13.3** 119 14** 135 26** 118 23** 128 11.6** 168 10.8** 177
70% 13.3** 119 16.8** 162 26** 118 23** 128 10.8** 156 7** 115
50% 10.2** 92 17.2** 165 25** 114 24** 133 13** 188 7.1** 116
Kinetin
30% 9.9** 89 12.4** 119 24** 109 16** 89 13** 188 7.2** 118
90% 8.9** 80 14.4** 13822 10024** 133 14** 203 8.1** 133
70% 15.3** 138 15.1** 145 28** 127 20** 111 12** 174 7** 115
50% 9.2** 83 15.5** 149 36** 164 21** 117 10** 145 6 98.
Mixture hor-
mones
30% 9.2** 83 16.1** 155 26** 11818 1009** 130 5** 82
90% 12** 108 15.2** 146 32** 145 32** 178 13** 188 9** 147
70% 11.6** 104 21.5** 206 31** 141 28** 156 13** 188 9** 147
50% 11.9** 107 15.5** 149 21** 95 22** 122 13** 188 12** 197
Putrescine
30% 12** 108 17.5** 168 21** 95 23** 128 13** 188 11** 180
90% 10.8** 97 11.9** 114 26** 118 20** 111 18** 261 14** 229
70% 12.4** 112 14.6** 140 20** 91 20** 111 16** 232 14** 229
50% 19.9** 179 12.4** 119 23** 104 24** 133 12** 174 12** 197
Spermine
30% 14.7** 132 14.1** 135 21** 95 24** 133 12** 174 8** 131
90% 12.9** 116 12.6** 12122 10020** 111 12** 174 7** 115
70% 15.8** 142 19.6** 18822 10018 10010** 145 10** 164
50% 12.3** 111 17.2** 165 20** 91 18 10010** 145 8** 131
Mixture poly
amines
30% 11.5** 104 17.5** 168 19** 86 18 1008** 116 8** 131
0.01 0.22 0.35 0.37 0.34 0.23 0.2
LSD
0.05 0.16 0.30 0.31 0.27 0.17 0.15
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
799
Table 6. Interactive effect of drought stress and phytohormones or polyamines on potassium, calcium and sodium (mg·gm–1
plant dwt) of maize genotype Bashaie r.
K+ Ca++ Mg++
Treatm ent F.C shoot % Root % Shoot % Root % shoot % Root %
90% 12.9 100 10.2 100 30 100 36 100 24 100 14 100
70% 14.5** 112 8.9** 87 40** 133 44** 122 28** 117 16** 114
50% 15.3** 118 11.3** 111 33** 110 44** 122 25** 104 18** 128
Control
30% 16** 124 13.1** 128 28** 93 40** 111 26** 108 12** 85
90% 13.3** 103 12.8** 125 35** 116 41** 114 36** 150 14 100
70% 24.6** 190 11.2** 109 34** 113 38** 106 23** 96 16** 114
50% 26.5** 205 11.4** 112 34** 113 42** 117 30** 125 18** 128
IAA
30% 26.8** 208 14.3** 140 30** 100 44** 122 30** 125 28** 200
90% 14** 108 18.2** 178 50** 166 39** 108 48** 200 17** 121
70% 20.5** 159 13.4** 131 30** 100 42** 117 33** 137 18** 128
50% 22** 170 15.5** 152 62** 206 41** 114 29** 121 19** 135
GA3
30% 18** 139 20.5** 201 50** 166 36 100 30** 125 20** 142
90% 13.3** 103 11** 108 46** 153 36 100 40** 166 14 100
70% 15.7** 122 14.4** 141 45** 150 36 100 33** 137 18** 128
50% 17** 132 10.2 100 36** 120 40** 111 29** 121 18** 128
Kinetin
30% 15** 116 19.9** 195 36** 120 41** 114 32** 133 18.5** 132
90% 13 101 10.6** 104 38** 126 39** 108 25** 104 25** 178
70% 14** 108 21.8** 214 38** 126 36 100 36** 150 14 100
50% 21** 163 16** 157 36** 120 54** 150 30** 125 21** 150
Mixture
hormones
30% 39** 302 16** 157 36** 120 40** 111 26** 108 17** 121
90% 14** 108 10.9** 106 54** 180 44** 122 28** 116 21** 150
70% 18** 139 14** 137 39** 130 43** 119 21** 87 18** 128
50% 20** 155 19.5** 191 40** 133 40** 111 24 100 18** 128
Putrescine
30% 20.8** 161 18.9** 185 42** 140 46** 128 23** 96 16** 114
90% 11** 85 17.8** 174 40** 133 47** 131 54** 225 22** 157
70% 20.8** 161 10.2 100 48** 160 41** 114 25** 104 25** 178
50% 15** 116 11.6** 114 32** 106 46** 128 26** 108 22** 157
Spermine
30% 18.7** 145 17.8** 174 36** 120 40** 111 26** 108 18** 128
90% 23** 178 24.6** 241 3**6 120 40** 111 32** 133 18** 128
70% 16** 124 19** 186 46** 153 35** 97 26** 108 20** 143
50% 16** 124 15.5** 152 62** 206 36 100 44** 183 18** 128
Mixture poly
amines
30% 17** 132 14.3** 140 36** 120 36 100 26** 108 27** 193
0.01 0.30 0.25 0.4 0.42 0.38 0.35
LSD
0.05 0.25 0.21 0.36 0.35 0.33 0.30
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
800
Table 7. Interactive effect of drought stress and phytohormones or polyamines on number of grains per ear, 1000 grain weight
(gm), and ne t yie ld (Arda b. Faddan-1) of ma ize geno type Ne f ert iti.
% yield % 1000 grain weight % No, of grains F.C Treat ments
100 21.1 100 324 100 580 90%
88 18.6** 95 308** 92 536** 70%
- - - - - - 50%
- - - - - - 30%
Control
107 22.7** 104 336* 104 601** 90%
107 22.6** 105 340** 102 591 70%
25 5.23** 102 330 24 141** 50%
- - - - - - 30%
IAA
95 20.2** 93 300** 103 597** 90%
88 18.6** 98 316 95 550** 70%
- - - - - - 50%
- - - - - - 30%
GA3
95 20.1** 106 344** 101 590 90%
72 15.2** 73 236** 97 560** 70%
- - - - - - 50%
- - - - - - 30%
Kinetin
99 21 97 314 107 623** 90%
55 11.6** 58 189** 102 590 70%
- - - - - - 50%
- - - - - - 30%
Mixture hor-
mone
125 26.5** 116 377** 116 674** 90%
95 20.2** 102 329 99 572 70%
62 13** 93 300** 85 492** 50%
- - - - - - 30%
Putrescine
114 24** 122 396** 122 708** 90%
106 22.5** 112 364v 96 559** 70%
71 15** 97 313 88 513** 50%
- - - - - - 30%
Spermine
123 26** 105 340** 117 680** 90%
118 25** 115 374** 112 650** 70%
61 12.8** 93 301** 76 440** 50%
- - - - - - 30%
Mixture poly
amines
0.49 15.51 15.89 0.01
0.37 11.66 11.94 0.05 LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
801
Table 8. Interactive effect of drought stress and phytohormones or polyamines on number of grains per ear, 1000 grain
weight (g m), and net yield ( Ardab. F addan-1) of maiz e genotype B a shaier.
% yield % 1000 grain weight % No, of grains F.C Treatm ent s
100 27 100 380 100 680 90%
95 25.7** 99 376 96 654* 70%
78 21** 97 369* 88 600** 50%
- - - - - - 30%
Control
114 30.8** 105 398** 108 733** 90%
110 29.9** 102 388 104 709** 70%
100 27 97 370* 102 695 50%
32 8.6** 58 220** 63 425** 30%
IAA
115 31** 111 424** 111 758** 90%
99 26.8 105 398** 97 663 70%
76 20.4** 100 380 77 525** 50%
37 9.9** 70 265** 59 400** 30%
GA3
106 28.6** 102 390* 103 698 90%
87 23.5** 98 374 82 558** 70%
79 21.4** 95 362** 77 526** 50%
32 8.6** 57 216** 52 354** 30%
Kinetin
114 30.8** 102 388 110 751** 90%
103 28** 101 384 102 694 70%
86 23.2** 97 370* 89 606** 50%
44 12** 74 280** 70 474** 30%
Mixture hor-
mone
126 34** 111 240** 114 772** 90%
112 30.3** 100 380 111 756** 70%
101 27.2 98 374 102 695 50%
68 18.3** 81 306** 87 590** 30%
Putrescine
125 33.7** 114 434** 105 715** 90%
111 30** 106 404** 103 700 70%
93 25** 101 384 93 631** 50%
56 15** 81 308** 74 505** 30%
Spermine
124 33.4** 113 430** 107 731** 90%
114 30.9** 107 406** 108 732** 70%
99.9 26.9 101 384 98 665 50%
62 16.8** 80 305** 81 550** 30%
Mixture poly
amines
0.59 13.18 27.69 0.01
0.44 9.91 20.81 0.05 LSD
* Significant difference and ** highly significant difference as compared with relative control.
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
802
phytohormones or polyamines treatment considerably in-
creased the number of grains per ear and the 1000 grain
weight up to 70% F.C. Additionally putrescine and IAA
increase this number at the level of 50% F.C.
The data of the crop yield of maize genotype Bashaier
in Table 8 was interesting:
1) It produced a suitable amount of crop yield up to
50% F.C (It produce 21 Ardab/feddan compared to 27
Ardab/feddan at 90% F.C) note that the sensitive geno-
type did not produce any crop yield at 50% F.C.
2) Phytohormones or polyamines give a crop yield
more or less similar to that recorded in the relative con-
trol up to 50% F.C. This was more pronounced in poly-
amines than in phytohormones. Moreover most of these
activators enhanced the crop yield to 70% F.C in relation
to the relative control. This was also more pronounced in
polyamines & IAA treated plants.
3) Phytohormones or polyamines give a suitable amount
of crop yield at the level of 30% F.C (The level which did
not give a crop yield in this genotype)
5. Discussion
The phenological characteristics (dry matter yield and
leaf area) of the field experiment recommended the
drought tolerance of maize genotype Bashaier and the
susceptibility of maize genotype Nefertiti. Accordingly
the growth of maize genotype Bashaier remained mostly
unchanged at mild drought stress whereas the growth of
maize genotype Nefertiti dropped even at the lower level
of drought stress, also the percent of reduction of the
studied growth parameter at sever drought was much
more higher in maize genotype Nefertiti than maize ge-
notype Bashaier. Accordingly, at the level of 30% F.C.
The percent of reduction in the dry matter of leaves and
stems of maize genotype Nefertiti was 62% & 75% re-
spectively, while in maize genotype Bashaier it was 20%
& 51% respectively. The differences in the growth crite-
tria among species and cultivars might be used as a suit-
able selection criterion for the drought tolerance of these
species and genotypes. The inhibitory effect of drought
on growth parameters could be attributed to the osmotic
effect of water stress [26,34,35]. Also, the reduction of
yield may be ascribed to the harmful effect of soil mois-
ture stress and nutrient balance disorder in root media
[36], or reduced rate of new cell production may be make
additional contribution to the inhibition of growth
[37-39]. The reduction in growth criteria due to drought
stress might be related to disturbance of water flow from
root to shoot [40], decrease in water potential of cell sap
[41], or inhibition of cell division [42].
The values of leaf area are varied among the two
drought stressed maize genotypes. They were much higher
in mai ze genotype Bashaier than in maize genotyp e Nefer-
titi. Also the reduction in the leaf area was much more
pronounced in maize genotype Nefertiti than in maize
genotype Bashaier. Along with this the photosynthetic
pigments remained more or less unchanged in maize ge-
notype Bashaier and decreased highly significantly in
maize genotype Nefertiti, which might improved the pho-
tosynthetic apparatus in maize genotype Bashaier than in
maize genotype Nefertiti. The ability of the plants to in-
crease its green area could be increased its drought tol-
erance [26]. This was found to be linked with the effi-
ciency of photosynthesis apparatus and consequently the
production of photoassimilates in the two maize geno-
types. [43,44] reported that, the reduction in leaves area
by drought stress may be due to a reduction in leaf ex-
pansion, probably due to the effect of drought stress on
cell division or cell expansion or both. [45] reported that,
the reduction observed in the leaf area and dry weight of
the drought stressed plants can be attributed to the chan-
ges in plant water relations under drought stress which
cause a reduction in meristem activity as well as cell
elongation [46], thereby inhibiting leaf expansion [47].
The observed decrease in dry weight of the drought-
stressed plants can be traced to the scanty recovery of
leaves following limited photosynthesis production [45].
[48] proposed that, the death of old leaves due to the
drought stress in the tissue would prevent the supply of
nutrients or hormones to emerging leaves, and reducing
leaf area. [49] concluded that a part from decreased growth
might be attributed to the reduction in the leaf area and leaf
number. The death of expanded leaves leading to decrease
in photosynthetic leaf area [50]. Leaf area reduced signifi-
cantly under water stress [51]. Reduction in the leaf area
by water stress is an important cause of reduced crop yield
through reduction in photosynthesis [51,52].
In recommendation when this plants sprayed with poly-
amines or phytohormones, the dry matter yield, leaf area,
and photosynthetic pigments enhanced markedly, which
indicated the complete correlation among the three pa-
rameters. [53] study the effect of drought stressed maize,
cowpea and broad bean plants and found that while the
photosynthetic pigments decreased significantly in maize
they remained more or less unchanged in cowpea and
broad bean plants, consequently the dry matter produc-
tion in maize was much more affected by drought stress
than in cowpea and broad bean plants. They also re-
ported that when these plants sprayed with phytohor-
mones or polyamines there is a marked stimulatory effect
in green area and consequently the photosynthetic pig-
ments which consequently accumulated the dry mass of
the three tested species [54] working with drought stressed
wheat cultivars and found that, the reduction in photo-
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
803
synthetic pigments was more pronounced in drought sus-
ceptible than in drought resistant cultivars. Other inves-
tigators reported a reduction in chlorophyll contents un-
der drought conditions [55,56]. The reduction in total
photosynthetic pigments has been reported to be related
to the activation of chlorophyllase, which catalyses the
catabolism of chlorophyll [57]. [58,59] reported that the
degradation of thylakoid can occur in response to water
stress. The enhancement of chlorophyll degradation in
leaves of stressed plants can probably be due to the dis-
turbance in hormonal balance. Such disturbance may be
manifested by dimensioned kinetin biosynthesis and in-
creased abscisic acid. The former is known to inhibit
chlorophyllase activity whereas the letter is known to
accelerate it [60].
The differences in the responses to drought stress be-
tween the two selected maize genotypes were mirrored
by the differences in the absorption, accumulation and
compartmentation of K+, Ca++ and Mg++ in the different
organs of the two genotypes. Our data reveal that while
drought stress had a marked stimulatory effect in the
absorption and accumulation of K+, Ca++ and Mg++ in
different organs of maize genotype Bashaier it on other
hand, significantly inhibited the accumulation of these
cations in the different organs of maize genotype Nefer-
titi. It has been well known that osmotic regulators in-
clude many important small molecules such as potassium,
soluble sugars, proline and petaine [61-63]. These small
molecules are also important physiological indicators for
evaluating osmotic adjustment ability [64].
The maize genotype Nefertiti produced a crop yield
(number of grains per ear, 1000 grain weight and the
total yield per feddan) up to only 70% F.C, and failed
completely to give crop yield at the levels of 50% & 30%
F.C. while treatment with polyamines produce crop yield
up to 50% F.C. Additionally all of used polyamines in-
creased the crop yield at the normal condition (90% F.C)
as compared with untreated plants. The crop yield of
plants treated with putrescine, spermine or mixture po-
lyamines was 26.5, 24, or 26 Ardab/feddan compared to
21.14 (at the normal level). It is worthy to mention that
IAA is the only phytohormone which produced a crop
yield up to 50% F.C (5.23 Ardab/feddan), although the
other phytohormones considerably enhanced the plant
growth during the vegetative stage. This unexpected phe-
nomenon seemed to be complicated and need a numer-
ous and further studies.
On the other hand the production of crop yield in ma-
ize genotype Bashaier under different treatments was
interesting. This genotype produce 21 Ardab/feddan of
maize grain at the level of 50% F.C, which considered an
excellent results (note that the sensitive cultivar produce
the same amount at the normal condition), on the oppo-
site to the sensitive cultivar, phytohormones treatment
increased the crop yield over the control value of the this
drought tolerant cultivar up to 70% F.C, also the pro-
duced crop yield of IAA treated plants at 50% F.C was
similar to that of control plants. Also a pronounced in-
creased the crop yield was obtained up to the level of
70% F.C as a results of polyamines treatment in com-
parison with the relative control values. Moreover Putre-
scine increase the crop yield by 1.24 Ardab/feddan over
the control at the level of 50% F.C. Interestingly at the
level of 30% F.C. while the only drought stressed plants
did not give a crop yield, the phytohormones or poly-
amines yielded a suitable amount of maize grain at the
level of 30% F.C. The data also reveal that the improve-
ment of crop yield was much more pronounced in poly-
amines treated plants than phytohormone ones. Putre-
scine was also superior in produce 18.3 Ardab/feddan at
30% F.C in relation to 27 Ardab/feddan in relative con-
trol plants (A very interesting results). Stress during dif-
ferent growth stages might decrease translocation of as-
similates to the grains, which lowered grain weight and
increased the empty grains. There are some reports indi-
cated that lower soil moisture might inhibit photosynthe-
sis and decrease translocation of assimilates to the grain
which lowered grain weight [65,66]. Moreover, water
stress might lead to a considerable increase in secondary
rachis branch abortion and resulted in a reduction in
spikelets number per panicle [67]. In addition, drought
stress could curtail the kernel sink potential by reducing
the number of endosperm cells and amyloplasts formed
[68,69]. Therefore, the rate of reducing in grain weight is
correlated to the reduction in the capacity of the en-
dosperm to accumulate starch, in terms of both rate and
duration [69].
On the other hand, some studies show that there would
be significantly higher gain in biomass (dry Ministry
weight) after stress imposed. This dry weight would be
associated to the cell division and new material synthesis
[67,70]. Increasing the number of filled grains might be
due to the contribution of carbohydrates from current
photosynthesis which have been more and efficiently
would translocated into the grain and thus increased the
grain yield [71]. Usually, water stress at grain filling in-
duces early senescence and shortens the grain filling pe-
riod but increases remobilization of assimilates from the
straw to the grains [72,73]. The early senescence induced
by a moderate water-deficit during grain filling can en-
hance the remobilization of stored assimilates and accel-
erate grain filling of rice [69,71].
Other experiences show that plants could cope with
stress condition exhibiting morphological alteration such
Interactive Effects of Drought Stress and Phytohormones or Polyamines on Growth and Yield of
Two M (Zea maize L.) Genotypes
Copyright © 2011 SciRes. AJPS
804
as root characteristic in which affect grain formation [74].
The slow grain-filling rate and low grain weight of infe-
rior spikelets have often been attributed to a limitation in
carbohydrate supply [69].
It’s important to stress on the differential effects of the
using of phytohormones or polyamines from the vegeta-
tive stage to the fruiting stage among the two selected
maize genotypes. Exogenous application of any of the
growth promoters “phytohormones and polyamines”. Im-
proved the drought tolerance of the two maize genotypes
during vegetative stage through the improvement of pho-
nological characteristics and the physiological behavior
which consequently and interestingly induce a surprising
improvement in the crop yield especially in maize geno-
type Bashaier (the drought tolerant cultivar), They pro-
duce a suitable amount of crop at the level of 30% F.C
(the level which did not give any crop yield in plants
subjected only to 30% F.C), also IAA is the only phyto-
hormone which give a crop yield in maize genotype Ne-
fertiti up to 50% F.C. Why the phytohormone did not
give a crop yield in maize geno type Nefertiti beyond 70%
F.C Although they improved Interactive Effects of Drou-
ght Stress and Phytohormones or Polyamines on Growth
and Yield of Two M(Zea maize L) Genotypes.
The growth and the physiology of this cultivar during
the vegetative stage and also why these phytohormones
make this considerable improvement in crop yield only
in maize cv. Bashaier? The answer seemed to be com-
plicated which might associated with the genotypic va-
riation rather than the growth activators it self which
might indicated the great variation in the interaction be-
tween the response of the two maize genotypes with the
different growth activators. The situation was very com-
plicated and might include many physiological processes
and also may be associated with induction of phlorogen
and phytochrome (phytohormones responsible for flow-
ering and fruiting stage). So, and according to our data in
maize genotype Nefertiti the role played by these activa-
tors was differed from vegetative to flowering stage and
the use of these activators only up to vegetative growth is
not a sign for improving of crop yield. The diversity and
complexity between the stress factors and gene action
among the different species and genotypes as well as the
different growth stages, still open question.
In conclusion maize genotype Nefertiti in addition to
its sensitivity to drought stress, is also not responded
enough to exogenous application of the used growth pro-
moters especially phytohormones except for IAA to some
extent. On the other hand the drought stressed maize ge-
notype Bashaier was also strongly responded to phyto-
hormones or polyamines treatments. Exogenous applica-
tion of polyamines seemed to be more effective than
phytohormones. Putrescine might be the superior poly-
amine. Finally and according to these results, this study
opened many fields of studies in the future, this fields
might linked with the breading programs (the con- trast-
ing behaviors of the produced cultivars and lines), from
one hand and the differential responses of the added
plant promoters. Also it’s difficult to recommend the role
of any of these plant promoters before the flowering and
fruiting stages.
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