Open Journal of Soil Science, 2012, 2, 282-288 Published Online September 2012 (
Physiological Effects of Chitosan Coating on Wheat
Growth and Activities of Protective Enzyme with Drought
Defang Zeng*, Xinrong Luo
School of Resource and Environmental Engineering, Wuhan University of Technology, Hubei Key Laboratory of Mineral Resources
Processing and Environment, Wuhan, China.
Email: *
Received March 17th, 2012; revised April 20th, 2012; accepted May 3rd, 2012
Seedling period is an important stage of plant growth. This research was mainly to analysis the influence of chitosan on
wheat seedling growth and physiological mechanisms under drought stress. The results showed that the group coated
with chitosan significantly improved the growth index such as germination rate, wet weight, root length, root active, and
impacted physiological indices such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)), the con-
tent of malwondialdehyde (MDA) and chlorophyll compared with CK under drought stress. Activities of POD, CAT
and SOD increased and then decreased, the content of MDA increased under drought stress. But variation rates of the
group coated with chitosan were slower than that of CK, which indicates that chitosan can significantly improve anti-
oxidant enzymes activity to clear timely active oxygen and reduce the content of MDA so as to alleviate the degree of
damage in the drought stress and make seedlings grow better. The results also showed that chitosan improved chloro-
phyll content than that of CK, which demonstrated that chlorophyll content significantly influenced the photosynthetic
efficiency of the mutant and added wheat above ground biomass and the field experiment results showed that chitosan
increased yield 13.6% than that of CK.
Keywords: Biologicalstress; Chitosan; Drought Stress; Protective Enzyme; Physiological Features
1. Introduction
Abiotic stress is the major cause of crop loss worldwide
[1,2]. Drought is one of the greatest abiotic stress to
agriculture, inhibiting plant growth and reducing produc-
tivity [3,4]. Wheat is the most widely planted in the main
crop zone, about 70% of which are droughty, or semiarid
areas, the demand for crop supply has increased corre-
spondingly [5,6]. So it is urgent to improve wheat yields
even under the unfavorable conditions. Depending on di-
fferent statuses of soil water, biochemical changes to va-
rious extents, occurred in wheat grains. Polysaccharide
was a more effective way to improve the capacity of
drought resistance [7,9]. The existing results [10-13]
showed that certain concentration of polysaccharide can
enhance the capacity of cold, salt and drought resistance
for crops. Chitosan and its derivatives from aquatic pro-
ducts such as waste shrimp, crab shells were mainly in-
exhaustible marine resources. For its non-toxic, non-
pollution and biodegradation, in recent years they have
been widely researched and applicated as efficient green
pesticides and plant growth regulator in agricultural
fields [14,15]. Therefore, it has become a hot issue to
elucidate the possible responses and adaptation of plants
to drought.
The present study aimed to investigate whether the
agent can improve the ability of fighting drought for
plants, so as to provide theoretical reference for the deve-
lopment and application of chitosan for crops. Thronght
the study, chitosan mainly through raising the activities
of POD, CAT and SOD, and other biological resistance
such as seed germination and germination potential, leaf
length, root length, chlorophyll concentration, so as to
improve drought resistance and increase wheat yield.
2. Materials and Methods
2.1. Materials
2.1.1. Main Experimental Apparatus
Electron constant speed mixer GS28B (Shanghai Anting
Electronic Instruments Plant, Shanghai, China), high pre-
ssure steam sterilizer YXQ-SG46-48SA (Shanghai Boyi
Industry Co. Ltd., Shanghai, China), constant temperature
*Corresponding author.
Copyright © 2012 SciRes. OJSS
Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
and humidity incubator WS-01 (Hubei Huangshi Heng-
feng Medical Instrument Co., Ltd., Hubei, China), elec-
tronic balance (FA2004, ShanghaiYuefeng Instrument
Appearance, Ltd., Shanghai, China), warm up hygrometer
STH950 (Summit, USA), biological microscope BX41-
12HO2 (Olympus Corp., Japan) and petri dishes (90 cm
dia., Shanghai Yuejin Medical Treatment Instrument
Plant, Shanghai, China), 722 type uvvis spectrophoto-
meter (Beijing at general chromatography instrument Co.,
LTD); TDL-5 A desktop centrifuge (Shanghai anting
scientific instruments plant); SPAD-502, Minolta, Japan.
2.1.2. Main Experi me ntal Reag ents
Glacial acetic acid and no water ethanol, 95% ethanol,
quartz sand, calcium carbonate powder are domestic ana-
lysis pure, wheat seeds (Hubei provincial seed group com-
Chitosan was dissolved at 0.2% C, 0.4% C, 0.6% C,
0.8% C and 1% C (w/v) into aqueous solutions of acetic
acid at 1% C (w/v). The pH of solution was adjusted to
6.0 using 1% NaOH.
2.2. Experimental Design
The wheat seeds coated at 1:50 (w/w) with chitosan and
designed a control group (CK) were subjected to soil
water treatments of 75%, Until all seeds sprouted in 7
days after they were sown, relative water content was
controlled at 30% for 10 days, then changed at 75%. All
kinds of growth indexes in seedlings were measured un-
der drought stress every two days. The date of fertilizer
applications and management were the same for all treat-
ments. The trial design was a completely randomized
plot design with three replications.
2.3. Collection and Measurement of Parameters
The first outspread leaf from top was cut and wiped with
a wet pled. Plant roots were sampled with a shovel in 0 to
60 cm soil depth below the wheat stem and separated
from the soil by washing over a sieve. All samples were
immediately frozen under liquid N, and then stored at
super-low refrigerated conditions (–20˚C) for enzyme
(SOD, POD, CAT), MDA and chlorophyll further analy-
2.3.1 Germination Rate
According to the seed test procedures methods of inter-
national seed association (ISTA), germinating energy
(GE), germination percentage (GP) and germination in-
dex (GI) were as follow:
GE %CE100%
GP%D E100%
GI%F G100%
where C is the number of germinated seeds on the third
day, D is the number of germinated seeds on the seventh
day, E is the number of total seeds investigated, F is the
number of germinated seeds one day; and G is the days
of seeds germination.
 
Percentage of moisture%WWW 1
where W1 is fresh weight of seedling; W2 is dry weight
of seedling investigated.
Root activity was determined by TTC (chlorinated
three phenyl four nitrogen method). The following for-
mula was used to calculate vitality of root:
 
Vitality of rootmggh
TTC reduction amount mg
root weight gtime h
2.3.2. Malon aldehyde (MDA)
The MDA content was determined [16] (TBA) as de-
scribed by Heath and Packer. The absorbances at 450 nm,
532 nm and 600 nm were determined with an ultraviolet
spectrophotometer. The MDA contents were calculated
using the following formula:
532 600450
D532, D600 and D450 were the absorbance valve in 532 nm,
600 nm and 450 nm of extraction.
2.3.3. A ssay of Pro te ct ive Enz ym e
In the different dry conditions, measurements of SOD,
POD, and CAT activities were performed every 2days.
Roots were cut in different direction of each pot (contain-
ing two seedlings) with borer (2 cm), repeated in all the
pots of each treatment. SOD, POD and CAT were deter-
mined by the method described by Giannopolitis and
Ries [17].
2.3.4. Assay of Chl orophyll
Chlorophyll was determined using a chlorophyll meter
(SPAD-502, Minolta, Japan). Leaves for each genotype
in both well-watered and drought-stress conditions were
measured every 2 days after drought stress (30%) and the
following 3rd day after well-water treatment (75%). The
method for chlorophyll analysis was described by Arnon
2.3.5. Field Trial
Field trial was carried out to verify further whether the
efficacy of chitosan in the laboratory was stabilized, and
the effect on the yield was higher than that of CK. In this
Copyright © 2012 SciRes. OJSS
Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
test, the method of seed treatment was the same as that in
the laboratory experiment, the wheat seeds were coated
with chitosan in the proportion of 1:50 (w/w). The experi-
ment was conducted at Hubei Provincial Seed Group
Company. The experiments were designed as a rando-
mized block, and each treatment was replicated three
2.4. Statistical Analysis
All data presented were the mean values of six replicates
and were analyzed by Duncan’s multiple new range test
using SAS software. The small letters and capital letters
mean significance of difference under p < 0.05 level.
3. Results and Discussion
3.1. Effect of T on Wheat Seed Germination and
Seedling Growth
As can been seen in the Table 1, the influences of the
different concentrations on wheat germination abilities
were different. Along with the increasing concentration,
the effect was more obvious, and when in 0.8% C, ger-
mination abilities were the best, then dropped. growth
parameters of T were significantly higher than those of
Through the experiments, the results showed 0.8% C
was the best one to germination abilities. The next steps
were based on 0.8% C named after T.
The results of T on wheat seed germination and seed-
ling growth can be showed in Table 2. As can be seen,
Seeding height, fresh weight, percentage of moisture,
taproot length and vitality are regarded as the major in-
dexes to reflect crop condition with varying degrees. The
longer the root, the bigger surface plants absorb moisture
and nutrients improving the root activity, which can gua-
rantee supplying nutrients for seedling growth and make
seedlings thrive. The results indicated chitosan effect-
tively developed and raised seed germination rate in
some arid or semiarid condition. From Table 2, seeding
height, root length, and fresh weight greatly improved
compared to CK, especially in some arid or semiarid
condition, it was significantly higher.
3.2. In Dry Conditions, the Influence of T on
The influence of T on MDA can be showed in Figure 1,
MDA contents of wheat seedlings increased along with
the increase of stress time and the stress intensity streng-
then. but the increasing speed with chitosan was slower
obviously than that of CK in the drought stress condition.
When soil moisture back from 30% to 70%, the content
of MDA began to reduce, but the speed of T was faster
than that of CK. Cell membrane system is considered be
sensitive areas under the stress environment, MDA is one
of the membranous peroxide product, how many the
content of which can represent the degree of damage of
the cell membrane. The experimental results showed that
in the drought stress, MDA content of seedling treated
with T had significant reduction than that of CK, which
is good for quenching active oxygen, maintaining normal
function of biomolecules, protecting biological mem-
brane system and alleviating damage in drought stress. It
also found that chitosan has timeliness to relieve drought
damage for wheat seedlings.
3.3. Effects of T on Enzyme Related Index
The influence of T on enzyme related index can be
showed from Figures 2-4. Compared with CK, T im-
proved obviously the activities of POD, CAT and SOD
in the drought stress condition. The activities of wheat
seedlings decreased along with the increase of stress time
and the stress intensity strengthen. When soil moisture
back from 30% to 70%, the activities of POD, CAT and
SOD began to increase, but the speed of T was faster
than that of CK. SOD, CAT and POD are the protective
enzyme system to resist the damage of free radicals and
play an important role in defense mechanism in adversity
In a certain extent, the enzyme activities reflect plant
resistance. SOD catalyzes super oxygen free radicals to
form H2O2 with low activity; then is converted into H20
and O2 without oxidation activity by POD or CAT. Co-
ordination function of the three clears the reactive oxy-
gen species, reduce the level of membrane lipid peroxi-
dation, so as to improve the adaptability of resistance in
the adversity stress [19,20]. The experimental studies
found that T can significantly improve antioxidant en-
zymes activity of SOD, POD and CAT, strengthen the
ability of clearing active oxygen and alleviate the degree
of damage in the drought stress.
Table 1. Effects of different treatments on germination
Germination abilities
Treatments GE (%) GP (%) GI (%)
0.2% C 73.1 ± 1.5c 77.2 ± 1.3c 41.7 ± 0.5c
0.4% C 75.6 ± 1.6c 78.6 ± 1.2c 42.8 ± 0.6c
0.6% C 79.3 ± 1.3b 80.3 ± 1.2b 44.9 ± 0.8b
0.8% C 80.2 ± 1.2a 82.5 ± 1.1a 46.1 ± 0.7b
1.0% C 78.9 ± 1.4a 81.1 ± 1.2a 45.7 ± 0.4b
CK 65.9 ± 2.0 70.8 ± 1.5 40.2 ± 0.6
Values are expressed as mean ± standard error. Means with different letters
is significance different at p < 0.05.
Copyright © 2012 SciRes. OJSS
Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
Copyright © 2012 SciRes. OJSS
Table 2. Effect of T on wheat seedling growth.
Treatments Percentage of moisture (%) Seeding height (cm) Fresh weight (mg)Taproot length (cm) Vitality of root (mg·g1·h1)
T 86.1 ± 0.4b 14.23 ± 0.8b 568 ± 1.7a 5.32 ± 0.5a 0.42 ± 0.06a
CK 83.1 ± 0.6 13.85 ± 1.0 502 ± 1.3 4.16 ± 0.3 0.29 ± 0.09
3.4. Effects of T on Chlorophyll
The influence of chitosan on chlorophyll content can be
showed in Figure 5, the graph of chlorophyll content
both CK and chitosan indicated a gradual decline, but the
decreasing speed with chitosan was slower than CK dur-
ing the period of drought stress. When soil moisture back
from 30% to 70%, chlorophyll content began to increase,
but the speed of T was faster than that of CK Chlorophyll
is the material basis of photosynthesis, the content of
which directly influences the photosynthetic production.
This shows that chitosan can obviously increasesd pho-
tosynthetic capacity of seedlings, and accumulation of
organic matter, which is beneficial to the growth of the
young plants under drought stress condition.
Figure 1. Effect of T on MDA content under drought stress.
24681012 14
POD activity(U/mgprot)
3.5. The Comparative Result of Field Trials
Results of field trial showed that T noticeably improved
obviously the main performance indices such as tillers
per plant, spikes per plant,1000 grain weight and yield
(Table 3), Figure 6 also showed that ears of wheat
treated by chitosan were longer ,tillers were more, kernel
werefuller when comparing with CK. Tillers per plant
was improved by about 2.0 grain, spikes per plant was
improved by about 6.1 - 11.7 grain, 1000 grain weight
increased 2.1 - 5 g, yield per ha was in- creased by 13.6%.
It had indicated that the germination energy and germi-
nation rate in the laboratory were consistent with the
trend of increasing yield in field experiment. The results
show that T can effectively increase tillers per plant,
spikes per plant, 1000 grain weight and yield of wheat.
Figure 2. Effect of T on POD activity under drought stress.
CAT activity(U/mgprot)
3.6. Discussion
The content of leaf water reflects the water status of plant,
which is subjected to soil moisture and metabolism. Chi-
tosan coating can improve the content leaf water of seed-
lings. The experimental results showed that chitosan sig-
nificantly or very significantly increased the concen-
tration of chlorophyll compared with CK under drought
stress, which illustrates chitosan can enhance the photo-
synthesis performance and the accumulation of organic
matter on wheat seedlings. Under the drought condition,
a well developed root system absorbs more water to keep
the moisture stable. Chitosan coating can reduce the in-
hibition of roots and stem growth under drought stress,
which shows chitosan effectively promotes the develop-
Figure 3. Effect of T on CAT activity under drought stress.
SOD activity(U/mgprot)
Figure 4. Effect of T on SOD activity under drought stress.
Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
Table 3. Effects of T on wheat yield in the field trials.
Treatments No. of tiller (No./plant) No. of spike (No./plant)1000 grain weight (g) Yield (103 kg/ha)
T 5.2 ± 1.2c 48.1 ± 5.5a 46.3 ± 0.3c 469.3 ± 0.025a
CK 3.8 ± 1.6 36.4 ± 5.7 42.2 ± 0.5 413.4 ± 0.024
Values are expressed as mean ± standard error. Means within a column designated with different letters are significance different at p < 0.05.
many kinds of defense reactions [21]. The experimental
results showed that during the period of drought stress,
chitosan significantly or very significantly reduce the
content of MAD, increased the activity of COD, POD,
and CAT compared with CK under drought stress. Others
[22] researched influences of chitosan on rape resistance,
the tests showed that chitosan could raised up the active-
ties of those protection enzymes and hence to strengthen
the ability of drought tolerance of plants. The ability of
crops to resist drought was connected to the activities of
protective enzymes SOD, POD, and CAT and their de-
fensive function were closely correlated to the accumula-
tion of MDA, interacting as both cause and effect [23].
Chitosan can increase the activities of COD, POD, and
CAT, strengthen clearing ability of reactive oxygen spe-
cies and slow down the damage degree of the plasma
membrane, consequently reducing the accumulation of
MDA; But in CK group, the activities of COD, POD, and
CAT cannot clear the reactive oxygen in time, and their
protective function was lost and the membrane injury
further worsened, accumulating large MDA, which in
reverse inhibited the activities of the enzymes.
Figure 5. Chlorophyll content in the leaves of wheat seed-
lings under drought stress.
Through the above research results and the experi-
mental results, chitosan is considered to protect mem-
brane system, reduce the damage of drought stress and
strengthen drought resistance of plant. But it is not clear.
Some studies [24-26] showed that chitosan can induce
tobacco epidermal cells to produce NO and H2O2, which
can induce beans to close stomatals. Stomatal closure is
benefit to improve the water use efficiency, increase the
transpiration resistance of leaves and resist the drought
stress on plants. Lee [27] found that chitosan has the
similar function with abscisic acid (ABA) as an impor-
tant plant hormone, and plays an important role in plant
resistance to adverse environment. The study also found
that chitosan can decrease water transpiration of chilli
leaves and stem, to saving water in high temperature and
dry period [28]. It is not clear about the mechanism of
chitosan on drought resistance needing to be studied fur-
Figure 6. Contrast section photos of ears of wheat coated
with C and CK. The two on the left were treated by chito-
san, the two on the right were CK.
ment of root system and strengthens the capability of
water absorption, so as to enhance drought resistance of
wheat seedlings.
Plant produces the super oxide of free radicals and re-
active oxygen species in metabolic processes, and under
normal physiological conditions of plant, there is a ba-
lance between production and elimination of active oxy-
gen free radical. So plant does not exist any damage But
in the drought stress, when a large number of active
oxygen free radicals that harm the structure and function
of plant cells can not be cleared timely, the balance will
be destroyed, leading to the accumulation of MAD, one
of the ultimate products as a result of lipid peroxidation
damage by free radicals. Chitosan can recognize and
transmit the signal in plant. when identified, they induced
In conclusion, the results clearly suggest that chitosan
obviously improved wheat germination, and under
drought stress, the longer and more severe the drought
stress was, the lower the activity of the protective en-
zymes and the higher the content of MDA was, but the
protective enzymes of seedlings treated with T was
Copyright © 2012 SciRes. OJSS
Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
higher, and the content of MDA lower than that of CK. T
based on chitosan was helpful to improve the seed ger-
mination, seedling growth and enhances the stress resis-
tance of seedlings. Further more, chitosan increased
wheat yields up 13.6% than that of CK. So it had an im-
portant value of application and promotion in main pro-
duction zone of corn and can bring us obvious economic
and environmental benefits.
4. Acknowledgements
We express the appreciation to Wuhan Science and Tech-
nology Bureau of China for financial support (No.
201120922303). A special acknowledgement is given to
Wuhan University of Technology for experimental con-
ditions and technical support.
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Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme
with Drought Tolerance
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