research article an enhanced drought-tolerant...

Research ArticleAn Enhanced Drought-Tolerant Method Using SA-LoadedPAMPS Polymer Materials Applied on Tobacco Pelleted Seeds

Yajing Guan1 Huawei Cui2 Wenguang Ma2 Yunye Zheng2 Yixin Tian2 and Jin Hu1

1 Seed Science Center College of Agriculture and Biotechnology Zhejiang University Hangzhou 310058 China2 Yuxi Zhongyan Tobacco Seed Co Ltd Yuxi 653100 China

Correspondence should be addressed to Jin Hu jhuzjueducn

Received 27 April 2014 Revised 12 August 2014 Accepted 12 August 2014 Published 27 August 2014

Academic Editor Iliya Rashkov

Copyright copy 2014 Yajing Guan et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Drought is one of the most important stress factors limiting the seed industry and crop production Present study was undertakento create novel drought-resistant pelleted seeds using the combined materials with superabsorbent polymer poly(2-acrylamide-2-methyl propane sulfonic acid) (PAMPS) hydrogel and drought resistance agent salicylic acid (SA)The optimized PAMPS hydrogelwas obtained as the molar ratio of 2-acrylamido-2-methyl-propanesulfonic acid (AMPS) to potassium peroxydisulfate (KPS) andN N1015840-methylene-bis-acrylamide (MBA) was 1 000046 000134 The hydrogel weight after swelling in deionized water for 24 hreached 4306 times its own dry weight The water retention ratio (RR) of PAMPS was significantly higher as compared with thecontrol It could keep as high as 853 of original weight after 30min at 110∘C even at 25∘C for 40 d the PAMPS still kept RR at3367 PAMPS disintegration ratio increased gradually and reached around 30 after embedding in soil or activated sludge for60 d In addition there were better seed germination performance and seedling growth in the pelleted treatments with SA-loadedPAMPS hydrogel under drought stress than control It suggested that SA-loaded PAMPS hydrogel a nontoxic superabsorbentpolymer could be used as an effective drought resistance material applied to tobacco pelleted seeds

1 Introduction

Tobacco (Nicotiana tabacum L) originated from tropical andsubtropical area with abundant rainfall and high humidityand its water requirement is very high Most of the tobaccoplanting regions often lack necessary irrigation facilitieshence thewater deficiency has become themajor stress factorwith high potential impact on tobacco yield Seed pelletingtechnique is a new method of seed treatment Presently theplanting ratio of tobacco pelleted seeds in china has reachedaround 90 [1] Therefore research and development ontobacco pelleted seed with drought resistance are of greatsignificance

So far a few researches on drought-resistant coatingseeds put forward to add some water absorbent into thecoating agent [2] When field irrigation or rainfall comesthe water absorbent could absorb water from the soil toform a small ldquoreservoirrdquo and the stored water will comeout of the small ldquoreservoirrdquo to be utilized by the seeds orseedlings when soil is too dry to achieve drought resistance

However the water absorption ratios of traditional waterabsorbents such as polyacrylate and acrylic copolymer wereusually in the range from tens to hundreds [3ndash6] the limitedwater absorption capacity could not give full play to therole of the small ldquoreservoirrdquo In addition it is just a singlephysical method to improve seed drought resistance and thewater absorbent is difficult to play the role of ldquoreservoirrdquowhen there is lack of rainfall or irrigation the applicationof coating seeds in arid semi-arid or other areas of lessrainfall is limited Therefore combining the water absorbentand drought-resistant agents to form novel drought-resistantmaterials is particularly important to ensure the maximumseed germination and seedling establishment under droughtstress

Superabsorbent polymers (SAP) are new functional poly-mer materials containing strong hydrophilic groups that canabsorb and retain extremely large amounts of a liquid relativeto their own mass [7] Based on the characteristics of highwater absorption rate and good water retention they arewidely applied in agriculture forestry gardening petroleum

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 752658 9 pageshttpdxdoiorg1011552014752658

2 The Scientific World Journal

chemical industry medical health environment governanceand other fields [8 9]

2-acrylamide-2-methyl propane sulfonic acid (AMPS) isa kind of multifunctional water-soluble anionic monomerDue to the molecular structure of unsaturated double bondvinyl and the sulfonic acid functional groupwith strong anionand hydrophily AMPS has good performance of polymer-ization [10] and the water absorption ratio of its polymersit is known as a superabsorbent resin and can amount thethousands times of its own dry weight in general The AMPSmonomer has been widely applied in the synthesis of watertreatment agents adsorption and separation materials andwater absorbing and retention materials in high efficiency[10] However at present the information on the applicationof the AMPS monomer on pelleting seeds is lacking inliterature

Salicylic acid (SA) is widely regarded as an endogenousplant growth regulator which plays a significant role in thesignal transduction pathway of abiotic stresses in plants [11]Exogenous SA-induced enhancement in the resistance todrought have been observed in many plants such as maize[12] wheat [13] and rice [14] In a study soybean seedssoaking in salicylic acid caused a positive effect on theaccumulation of some ions and antagonists or modifyingthe inhibitory effect of drought stress [15] Sharafizad et al[16] found that wheat seed soaking treatment with SA in lowconcentration at low level of drought stress could decrease thegermination time and increase the germination percentageHowever the effect of SA loaded in superabsorbent polymerson plant drought resistance has not been reported

The poly(2-acrylamide-2-methyl propane sulfonic acid)(PAMPS) hydrogel was prepared and its synthetic formulawas optimized in this study Owing to high water absorbabil-ity and unique three-dimensional network structure PAMPShydrogel is considered as a controlled release material bycontrolling the release of SA from coating agent and furtherimproves the seedling drought tolerance Therefore PAMPShydrogel was used in this study to determine the performanceof superabsorbent resin and SA was used as a drought-resistant chemical that was embedded into PAMPS resinThen the enhanced drought-resistant effect of the SA-loadedPAMPS hydrogel as coating agent was studied

2 Materials and Methods

21 Materials Tobacco seeds of ldquoHonghua Dajinyuanrdquo(HHDJY) and ldquoMSk326rdquo coating agent (talc and ben-tonite) and the adhesive were provided by Yunnan Provin-cial Academy of Tobacco Agricultural Sciences China 2-Acrylamido-2-methylpropane sulfonic acid (AMPS-H+) andsalicylic acid (SA) were purchased from Shanghai Wing Sci-ence and Technology Co Ltd Shanghai China Potassiumpersulfate (KPS) N N1015840-methylene-bis(acrylamide) (MBA)NaCl and NaOH were obtained from Shanghai DingguoBiotechnology Co Ltd Shanghai China All chemicals wereused as received and experiments were carried out applyingdouble distilled water (ddH

2O)

Table 1 Preparation of poly(2-acrylamido-2-methylpropane sul-fonic acid) (PAMPS) hydrogels

Sample code AMPSlowast (g) KPS (g) MBA (g)F1 35 0007 00105F2 35 0007 00350F3 35 0007 01050F4 35 0014 00105F5 35 0014 00350F6 35 0014 01050F7 35 0021 00105F8 35 0021 00350F9 35 0021 01050lowastAMPS is 2-acrylamido-2-methylpropane sulfonic acid KPS is potassiumpersulfate MBA is N N1015840-methylene-bis(acrylamide)

22 The Synthesis of PAMPS

221 The Preparation of Stock Solution AMPS-H+ wascrystallized from boiling methanol [17] 2-Acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na+) stocksolution was prepared by dissolving 35 g of AMPS-H+ in70mL of ddH

2O followed by addition of 15mL 30 wv

NaOH solution under cooling conditions Afterwards thesolution was neutralized by titration with 1M NaOH to pH700 Finally the volume of the solution was adjusted to100mL with ddH

2O

MBA was crystallized from warm acetone The MBAstock solution was prepared by dissolving 105 g of MBA inabout 90mL of ddH

2O and then adjusting the final volume

to 100mL with ddH2O (the concentration is 0105 gmL)

KPS stock solution was prepared by dissolving 0070 g ofKPS in 10mL of ddH

2O (the concentration is 0007 gmL)

For the hydrogel synthesis ddH2O was cooled under

nitrogen bubbling

222 Synthesis of Hydrogel The copolymerization of PAMPShydrogel was carried out in ddH

2O at 40∘C in the presence

of KPS as the initiator (Table 1) AMPS MBA and KPSstock solutions were mixed together according to the ratiosin Table 1 After bubbling nitrogen for 20min the glasstubes were sealed and immersed in 55∘C water bath andthe polymerization was conductedThe hydrogel would formwell after 6sim7 h

23 The Characteristics of the Hydrogel

231 Fourier Transform Infrared Spectroscopy AnalysisFourier transform infrared spectroscopy (FTIR) was used tocharacterize the presence of specific chemical groups in thematerials 001 g of PAMPS powder was ground along withKBr to form a disc and analyzed by using FTIR absorbancemode FTIR spectra were obtained in the range of wavenumber from 4000 to 500 cmminus1 (Nicolet 5700 ThermoNicolet USA)The FTIR spectra were normalized and majorvibration bands were associated with chemical groups

The Scientific World Journal 3

Table 2 The different formulas of tobacco seed pelleting agents

Treatmentlowast PAMPS (g) SA (g) Talc (g) Bentonite (g) Total weight (g)Control 0 0 7000 30 100P1 15 0 6850 30 100P2 25 0 6750 30 100S1 0 005 6995 30 100S2 0 010 6990 30 100S3 0 015 6985 30 100P1S1 15 005 6895 30 100P1S2 15 010 6840 30 100P1S3 15 015 6835 30 100P2S1 25 005 6745 30 100P2S2 25 010 6740 30 100P2S3 25 015 6735 30 100lowastPAMPS is poly(2-acrylamido-2-methylpropane sulfonic acid) hydrogel (F8) and SA is salicylic acid tobacco seed pelleting agents with different formulas thecontrol is the mixture of talc and bentonite without PAMPS hydrogel and SA P1 and P2 are mixtures of PAMPS hydrogel talc and bentonite without SA S1and S2 are mixtures of SA talc and bentonite without PAMPS hydrogel P1S1 P1S2 P1S3 P2S1 P2S2 and P2S3 are mixtures of SA-loaded PAMPS hydrogeltalc and bentonite F8 (shown in Table 1) is the PAMPS hydrogel synthesized by 35 g of AMPS (2-acrylamido-2-methylpropane sulfonic acid) 0021 g of KPS(Potassium persulfate) and 0035 g of MBA (N N1015840-methylene-bis (acrylamide))

232 Swelling Measurements in Water and Salt Solutions003 g (119898

0) of PAMPS powders was accurately weighed and

added in air-tight test bottles containing 300mL of ddH2O

or 09 (ww) NaCl solution After every 30min of PAMPSabsorbing solution (totally 24 h) at room temperature (25∘C)the residues of ddH

2O or NaCl solution in the container

were filtered with 250 micron nylon mesh filter bag and thePAMPS weight in the swollen state (119898

119889) was measured Its

weight swelling ratio (SR) was calculated as SR = ((119898119889minus

119898

0)119898

0) times 100 (gg) where the119898

0and119898

119889are the weights

of the hydrogels in dry state and swollen state for a given timerespectively

233 Water Retention Determination Certain amount (1198980

g) of swollen PAMPS (F8) (24 h) was measured in a beakerand the same weight of water in another beaker was usedas a control Beakers were placed in a chamber at 25∘Cand their weights were measured (119898

119889) every 5 days (totally

40 d) or they were kept in the chambers with different hightemperatures (30 50 70 90 and 110∘C) for 30min and thenwere weighted (119898

119889) The water retention ratio (RR) at room

temperature (25∘C) or high temperatures was calculated asRR = (119898

119889119898


0and119898

119889are initial

swollen hydrogel weight and weights obtained in a given timeat certain temperature respectively

234 PAMPS Disintegration Ratio Several pots were filledwith disinfected soil containing 40 (ww) water A certainamount (119898

0 g) of dried PAMPS (F8) in the form of bar

was embedded in soil and activated sludge Then the potswere placed in a chamber at 25∘C for 60 d and the soilmoisture level was maintained at 40 during the wholeperiodThe PAMPS samples were collected every 10 d rinsedgently with the ddH

2O to remove impurities on its surface

and finally dried at 60∘C to its constant weight (119898119889) The

PAMPS disintegration ratio (DR) was calculated as DR =

((119898

0minus 119898

119889)119898

0) times 100 (gg) where the 119898

0and 119898

119889are

the weight of hydrogel (g) before and after disintegrationrespectively

24 Preparation of Seed Coating Agent The SA-loadedPAMPS hydrogel (F8) was prepared SA powders (005 g (S1)010 g (S2) and 015 g (S3)) were weighted and dissolved in100mL of ddH

2O separately Next 15 g (P1) or 25 g (P2) F8

PAMPS powder was added into the above three SA solutionsfor full swelling and were taken out after 24 h These SA-loaded hydrogels (P1S1 P1S2 P1S3 P2S1 P2S2 and P2S3)were dried at 60∘C for 48 h and ground into powder forfurther use Eleven seed pelleting agents were prepared in thisstudy according to the formula given in Table 2

25 Preparation of Tobacco Pelleted Seeds Two grams oftobacco seeds was first coated with pure water and the abovepelleting agents in a cyclic alternating pattern until the seedsize reached 100sim125mm diameter (5sim8mL water per gramof naked tobacco seeds sprayed in total) then a secondlayer of pelleting agents and adhesive solution were suppliedcyclically until the seed size was 160sim180mm diameter Allseedswere pelleted by aminitype coater ldquoBY300Ardquo (ShanghaiChina) and were air-dried for 2 days at room temperature

26 Seed Germination and Seedling Growth under DroughtPelleted seeds were placed one by one in each well ofthe plastic plate which filled with disinfected soil matrixThree replications of 100 seeds each for each treatmentwere used And drought stress was imposed by adjustingthe soil moisture content to 40 of soil maximum watercontent Then seeds were incubated in a growth chamber(DGX-800E Safe Experiment Instrument Factory China)with 250120583molsdotmminus2sdotsminus1 light intensity and an alternating cycleof 8 h light at 30∘C and 16 h darkness at 20∘C for 16 days[18] Since the second day of experiment the germinated


00

02

04

06

08

10

12

500 1000 1500 2000 2500 3000 3500 4000

Abso

rban

ce 6269

1043712206

14546

1551716563 34436

Wavenumbers (cmminus1)

Figure 1 FTIR spectrum of PAMPS hydrogel

seeds were recorded daily for 16 days (standard germinationis when the root tip was approximately 1mm) Germinationindex (GI) and vigor index (VI) were calculated accordingto Hu et al [19] as follows GI = sumGtTt where Gtis the number of the newly germinating seeds in timesof Tt VI = GI times seedling dry weight In addition rootlength and seedling length were manually measured with aruler and seedling dry weight was determined after dryingat 80∘C for 24 h [20] These measurements were made onthirty randomly selected normal tobacco seedlings for eachreplicate [21]

27 Statistical Analysis Statistical analysis of all data wasdone by means of analysis of variance (ANOVA) using SASversion 80 software (SAS Institute Cary NC) Fisherrsquos leastsignificant difference (LSD) tests (119875 lt 005) were adoptedfor multiple comparison The percent data were transformedaccording to 119910 = arcsin [sqr(119909100)] before ANOVA

3 Results

31 Fourier Transform Infrared Spectroscopy Analysis ofPAMPS A typical spectrum of PAMPS copolymer wasshown in Figure 1 The characteristic absorption peak ofAMPS units was shown at 12206 cmminus1 due to the S=O groupThe peak was shown at 10437 cmminus1 due to the sulfonic acidgroups The amide I peak at 16563 cmminus1 (C=O stretching)and amide II peak at 15517 cmminus1 (NndashH bending vibration)were ascribed to the amide bond of PAMPS The NndashHstretching peak was shown at 34436 cmminus1

32 The Liquid Absorption Performance After 24 h liquidswelling weight swelling ratios (SR) of nine PAMPS hydro-gels were shown in Figure 2 Based on 35 g AMPS and00105 g MBA no matter how much KPS was applied F1 F4and F7 had lower weight swelling ratios in water and saltsolution compared with other prepared PAMPS hydrogelsmeanwhile there were no significant differences among thesethree hydrogels However F2 F5 and F8 after increasingthe amount of MBA to 00350 g had higher SRs than otherPAMPS hydrogels and their SRs increased obviously withthe increasing of KPS amount when water is used as aswelling medium In addition it was worth noting that theSRs of PAMPS hydrogels (F3 F6 and F9) turned to decline

if too much MBA (0105 g) were added into the polymerizedsystem and their SRs decreased quickly as the KPS amountincreased

The PAMPS polymerized according to the F8 formula inTable 1 had the highest SR in water and reached 4306 timesits own dry weight Its SR in salt solution was 373 whichwas a little lower than the SR of F2 and F5 PAMPS Thusthe F8 PAMPS was chosen to determine the change of weightswelling ratio along with the increasing of liquid absorptiontime at 25∘C (Figure 3) The SR of F8 PAMPS in water andsalt solution increased obviously and reachedmore than 4000and 350 times its own dry weight respectively after 3 h Inaddition the weight swelling rates during the first 30minof liquid absorption were evidently faster than other timeperiods

33 The Water Retention Properties The water retentionproperties of PAMPS hydrogel (F8) were tested underroom temperature (25∘C) (Figure 4) and higher temperatures(Figure 5) The results showed that the water retention ratio(RR) of PAMPS (F8) at a given time was always higher thanthat of control at 25∘C Compared with the 66 of originalweight of control after 40 d the F8 PAMPS hydrogel couldkeep the RR as high as 3367 (Figure 4) Even treated under110∘C for 30min the PAMPS still kept RR at 853 (Figure 5)

34 The Disintegration Characteristic The F8 PAMPS dis-integration ratio (DR) increased gradually as the time wenton (Figure 6) After embedding in soil and activating sludgefor 60 d the PAMPS disintegration ratio was 295 and35 respectively Moreover except for 20 d The F8 PAMPShydrogel had higher DR in activated sludge than in soil

35 Changes of Seed Germination and Seedling Growth underDrought Condition For both of tobacco varieties except S1and S3 other nine treatments significantly improved the seedgermination under drought stress compared with the control(Table 3) All of the GP GI and VI of P2S3 had the highestvalue in the above nine pelleting treatments especially forHHDJY ForMSk326 except theGP of P2S3 which was a littlelower than that of P2S2 the GI and VI were still higher thanother treatments

No significant differences were found in root length (RL)seedling length (SL) and dry weight (SDW) among thetreatments with P1 P2 S1 and the control in both of tobaccovarieties (Tables 4 and 5) However three treatments with25 g of PAMPS loaded with SA (P2S1 P2S2 and P2S3) inHHDJY and four treatments (P1S3 P2S1 P2S2 and P2S3) inMSk326 significantly improved the RL SL SFW and SDWas compared with the control and the most pronouncedeffect was recorded in P2S3 In addition seed pelleted withS3 inhibited significantly the seedling growth compared withthe control and other treatments irrespective of variety

4 Discussions

In this study the best super absorbent PAMPS hydrogelaccording to 1 000046 000134 (molmolmol) ratios of the


fg

cd

fg

b

e

g

a

f0

1000

2000

3000

4000

5000W

eigh

t sw

ellin

g ra

tio (

)

Wei

ght s

wel

ling

ratio

()

Water

e

a

c

e

a

d

e

b

e0

100

200

300

400

500

F1 F2 F3 F4 F5 F6 F7 F8 F9PAMPS PAMPS

NaCl solution

F1 F2 F3 F4 F5 F6 F7 F8 F9

Figure 2Weight swelling ratios of PAMPS hydrogels in water and salt solution for 24 h at 25∘C Lowercased lettersmean significant difference(a = 005 LSD) among different PAMPS hydrogels The formulas of different PAMPS hydrogels are shown in Table 1 Error bars representplusmnSE

0

1000

2000

3000

4000

5000

0 30 60 90 120 150 180 210 240

Wei

ght s

wel

ling

ratio

()

Wei

ght s

wel

ling

ratio

()

Water

0

100

200

300

400

500

0 30 60 90 120 150 180 210 240Time (min)Time (min)

NaCl solution

Figure 3 Weight swelling kinetics of F8 PAMPS polymers in water and salt solution at 25∘C F8 (shown in Table 1) is the PAMPS hydrogelsynthesized by 35 g of AMPS (2-acrylamido-2-methylpropane sulfonic acid) 0021 g of KPS (potassium persulfate) and 0035 g of MBA (NN1015840-methylene-bis(acrylamide)) Error bars represent plusmnSE

Table 3 Effects of different coating agents on tobacco pelleting seed germination under drought stress

Treatmentb HHDJY MSk326GP () GI VI GP () GI VI

Control 542 ca 284 c 4721 c 523 c 273 c 4330 dP1 634 b 338 b 5677 b 625 ab 332 b 5402 cP2 667 b 355 b 5974 b 634 ab 341 b 5567 cS1 567 c 292 c 5068 c 507 c 281 c 4005 dS2 647 b 345 b 5821 b 633 b 341 b 5726 bcS3 407 d 213 d 3886 d 433 e 225 d 4079 eP1S1 708 ab 379 ab 6535 b 653 ab 348 ab 5681 cP1S2 708 ab 389 ab 6661 ab 657 ab 355 ab 5796 bcP1S3 676 b 366 b 6296 b 653 ab 343 b 5738 bcP2S1 718 ab 385 ab 6676 ab 639 b 343 b 5716 bcP2S2 722 ab 393 ab 6808 ab 681 a 368 ab 6166 abP2S3 736 a 407 a 7111 a 671 ab 370 a 6332 aGP germination percentage GI germination index VI vigor indexaLowercased letters mean significant difference (a = 005 LSD) among treatments within the same varietybFor additional explanations see Table 2


Table 4 Effects of coating agents on seedling growth of Honghuadajinyuan (HHDJY) under drought stress

Treatmentb RL (mm) SL (mm) SFW (mg30 plants) SDW (mg30 plants)Control 802 ca 1575 b 1415 b 1584 cP1 866 bc 1680 ab 1478 b 1668 bcP2 887 bc 1682 ab 1504 ab 1686 bcS1 813 c 1566 b 1465 b 1557 cS2 915 ab 1680 ab 1543 ab 1740 abS3 756 d 1438 c 1309 c 1485 dP1S1 910 ab 1722 a 1575 a 1749 abP1S2 893 bc 1712 a 1545 ab 1665 bcP1S3 916 ab 1719 a 1530 ab 1734 abP2S1 913 ab 1734 a 1575 a 1749 abP2S2 917 ab 1734 a 1583 a 1764 abP2S3 938 a 1746 a 1613 a 1785 aRL root length SL seedling length SFW seedling fresh weight SDW seedling dry wightaLowercased letters mean significant difference (a = 005 LSD) among treatments within the same varietybFor additional explanations see Table 2

Table 5 Effects of coating agents on seedling growth of MSk326 under drought stress

Treatmentb RL (mm) SL (mm) SFW (mg30 plants) SDW (mg30 plants)Control 755 ca 1438 c 1309 c 1509 cP1 839 bc 1628 bc 1397 b 1614 cP2 842 bc 1634 bc 1420 b 1626 cS1 750 c 1445 c 1327 c 1605 cS2 841 bc 1631 bc 1418 b 1674 bS3 702 d 1356 d 1196 d 1419 dP1S1 848 bc 1631 bc 1493 b 1599 cP1S2 849 bc 1632 bc 1515 ab 1680 bP1S3 878 b 1673 ab 1508 ab 1710 abP2S1 885 ab 1665 ab 1508 ab 1704 abP2S2 883 ab 1678 ab 1523 ab 1740 aP2S3 916 a 1713 a 1583 a 1740 aRL root length SL seedling length SFW seedling fresh weight SDW seedling dry weightaLowercased letters mean significant difference (a = 005 LSD) among treatments within the same varietybFor additional explanations see Table 2

AMPS monomer to KPS and MBA was prepared It is worthnoting that when appropriate MBA was applied the liquidabsorption ratio of PAMPS could be improved by increasingKPS however it would be inhibited after improper amountof BMA was used The results suggested that MBA played animportant role in the preparation of PAMPS hydrogels havingless or more density network which is responsible for theswelling degree of the obtained hydrogels Also Nalampanget al [22] found the significant influence of crosslink density(MBA) on water content of AMPS-based hydrogels

The major FTIR absorption peaks of the PAMPS wereconsistent with related reports [17] and there was no otherimpurity peaks It was reasonable to conclude that the PAMPSwas polymerized successfully according to the synthesisrouteThewater absorption ratio could reach asmuch as 4306times its own dry weight which was far higher than othermaterials such as keratin-based hydrogel [3] polyacrylicacid sodium salt [4] and starch-based superabsorbent [6]

It might be because the linear polymers with sulfonategroups derived from AMPS exhibit extensive coil expansionin aqueous solutions even in a 5M NaCl solution [17]In addition due to the strongly ionizable sulfonate groupAMPS dissociates completely in the overall pH range andthe hydrogels derived from AMPS exhibit pH independentswelling behavior [23] Thus the prepared PAMPS hydrogelin this study was supposed to be able to adapt to various pHconditions However it still warrants further study

PAMPS exhibited slow disintegration characteristic insoil two months later about one-third of PAMPS weightdegraded and eventually broke down for nitrogen dioxidewater ammonia nitrogen and sodium ion and so forthThat meant it was nontoxic and environmentally safe to beused [24] Meanwhile the above characteristic of PAMPSenhanced its valid period and efficiency in practice Up tonow productions of super absorbent polymers in China havebeen widely used in food crops economic crops vegetables


0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater

Figure 4 Water retention kinetics of F8 PAMPS polymer at 25∘CError bars represent plusmnSE For additional explanations see Figure 3

80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()

PAMPSTemperature (∘C)

Figure 5 Water retention ratios of F8 PAMPS polymer at differenttemperature for 30min Error bars represent plusmnSE For additionalexplanations see Figure 3

flowers fruit trees lawn cultivation and so forth and provedto be effective [24]

However it was still unclear whether the PAMPS wassuitable for pelleting or could enhance tobacco seed droughtresistance as a small ldquoreservoirrdquo without interference of coat-ing agents Therefore studying the effects of different coatingagents including PAMPS on tobacco seedling establishmentwas necessary The results showed that the PAMPS alone (P1and P2) could improve the seed germination and seedlinggrowth under drought even the increase of seed GP GI andVI reached a significant level as compared with the controlIt suggested that the moisture absorbed by polymer fromsoil could be used gradually at stages of seedling growthThe similar results were also reported in soybean seed coatedwith starch-grafting super absorbent resin [2] andmaize seed

0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)

Time (d)Activated sludgeSoil

Figure 6 F8 PAMPS polymer disintegration ratio versus timehistories in soil and activated sludge Error bars represent plusmnSE Foradditional explanations see Figure 3

coated with polyacrylic acid sodium high water absorbentpolymer [25]

Moreover the P2S3 25 g PAMPS loaded with 015 g SAwas proved to be the best coating agent formula for tobaccoseed pelleting The positive effect of SA-loaded PAMPS onseed germination and seedling growth under drought stresswas better than that of the SA or PAMPS alone Salicylicacid improves germination by neutralizing free radicles oractive oxygen however it was important to note that 015 g SAalone had an obvious inhibition on seedling growth howeverafter loading the same amount of SA into PAMPS P1S3 andP2S3 distinctly turned to improve the seed germinationThismight be due to the high concentration of SA that negativelyinfluences the plant growth via inhibiting the activities ofprotective enzymes and promoting MDA production [26]Meanwhile the PAMPS hydrogel might have the controlledeffect on SA release to some extent to ensure the lowereffective concentration instead of the higher inhibiting con-centration

In addition it suggested that the likely reasons fordrought tolerance obtained by tobacco pelleting seeds withPAMPS coating agents were as follows one was that morethan 85 water absorbed by super absorbent polymer wasconsidered to be effective to the plant Like a miniaturereservoir as the rhizosphere soil moisture changed PAMPScould absorb and release water repeatedly to supply forplant roots utilization [27] Another study showed that thesoil structure was improved via PAMPS application whichcontributed to the improvement of soil porosity and airpermeability [28 29] Su et al [30] reported that as a resultof water in the soil absorbed by hydrogel soil thermalconductivity and temperature difference between day andnight reduced which would be good for the crop growth

In this study PAMPSwas used not only as superabsorbentpolymer but also as SA controlled release material that was


given full play to the dual-use value of PAMPS On the onehandwater released fromPAMPS improved tobacco seedlingestablishment under drought on the other hand the SAloaded in the PAMPS would be controlled released to furtherenhance the seedling drought resistance

5 Conclusions

In practice with the special ldquoreservoirrdquo characteristic the SA-loaded PAMPS hydrogel represents a potential dual-effect onimprovement of tobacco seed and seedling drought toleranceThis seed pelleting method with enhanced drought-resistantfunction may become a novel pathway to enhance seedestablishment under stresses However this method stillshould be verified in other crop seeds or there shouldbe an upgrade to this method with different chemicals toimplement in plant resistance against stresses

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Authorsrsquo Contribution

Yajing Guan and Huawei Cui contributed equally to thiswork

Acknowledgments

The research was supported by Project of Yunnan Provin-cial Tobacco Company (nos 2013YN10 and 2011YN10) theNational Natural Science Fund (nos 31201279 and 31371708)Special Fund for Agro-Scientific Research in the Public Inter-est (no 201203052) and Project of Science and TechnologyDepartment of Zhejiang Province (no 2013C32023) China

References

[1] W G Ma Y Y Zheng Y P Li Y Z Niu and Y S ChenldquoEffects ofwater priming duration anddifferent dryingmethodsof pelleted seed on germination of tobacco pelleted seeds andseedling growthrdquoActa Agriculturae Jiangxi vol 21 no 7 pp 29ndash31 2009

[2] Z Y Wang Z X Liu and Y C Wei ldquoEffects of super absorbentpolymers coating on photosynthesis and water use efficiency ofsoybeanrdquo Agriculture Research in the Arid Area vol 22 no 3pp 105ndash108 2004

[3] J M Cardamone ldquoKeratin spongehydrogel II active agentdeliveryrdquo Textile Research Journal vol 83 no 9 pp 917ndash9272013

[4] X Dang Y Zhang and Y Huang ldquoModeling of the effect ofsuper absorbent polymer on soil moisturerdquo Transactions of theChinese Society of Agricultural Engineering vol 21 no 4 pp 191ndash192 2005

[5] X H Zhou L W Liao and A H Shi ldquoSynthesis study for AA-HEMA copolymer super absorbents of high anti-saltrdquo Journalof Guangdong Industry Technical College vol 4 no 1 pp 16ndash192005

[6] Y Zhao and S Jiang ldquoEffect of porosity generators onabsorbency rate starch-based superabsorbentrdquo Transactions ofthe Chinese Society of Agricultural Machinery vol 40 no 10 pp126ndash128 2009

[7] F Nnadi and C Brave ldquoEnvironmentally friendly superab-sorbent polymers for water conservation in agricultural landsrdquoJournal of Soil Science and Environmental Management vol 2no 7 pp 206ndash211 2011

[8] S Francis M Kumar and L Varshney ldquoRadiation synthesisof superabsorbent poly(acrylic acid)-carrageenan hydrogelsrdquoRadiation Physics and Chemistry vol 69 no 6 pp 481ndash4862004

[9] L M Hansen D J Smith D H Reneker and W KataphinanldquoWater absorption and mechanical properties of electrospunstructured hydrogelsrdquo Journal of Applied Polymer Science vol95 no 2 pp 427ndash434 2005

[10] E Nadim F Ziaee H Bouhendi and A Askarizadeh ldquoStere-ocontrol study in radical polymerization of 2-acrylamido-2-methylpropane sulfonic acid in the presence of lewis acidsrdquoJournal of Macromolecular Science A Pure and Applied Chem-istry vol 48 no 7 pp 526ndash530 2011

[11] E Horvath G Szalai and T Janda ldquoInduction of abiotic stresstolerance by salicylic acid signalingrdquo Journal of Plant GrowthRegulation vol 26 no 3 pp 290ndash300 2007

[12] A Gunes A Inal M Alpaslan F Eraslan E G Bagci and NCicek ldquoSalicylic acid induced changes on some physiologicalparameters symptomatic for oxidative stress and mineral nutri-tion in maize (Zea mays L) grown under salinityrdquo Journal ofPlant Physiology vol 164 no 6 pp 728ndash736 2007

[13] E HorvathM Pal G Szalai E Paldi and T Janda ldquoExogenous4-hydroxybenzoic acid and salicylic acid modulate the effectof short-term drought and freezing stress on wheat plantsrdquoBiologia Plantarum vol 51 no 3 pp 480ndash487 2007

[14] M Farooq S M A Basra A Wahid N Ahmad and BA Saleem ldquoImproving the drought tolerance in rice (Oryzasativa L) by exogenous application of salicylic acidrdquo Journal ofAgronomy and Crop Science vol 195 no 4 pp 237ndash246 2009

[15] A M A Al-Hakimi ldquoCounteraction of drought stress onsoybean plants by seed soaking in salicylic acidrdquo InternationalJournal of Botany vol 2 no 4 pp 421ndash426 2006

[16] M Sharafizad A Naderi S A Siadat T Sakinejad and S LakldquoEffect of salicylic acid pretreatment on germination of wheatunder drought stressrdquo Journal of Agricultural Science vol 5 no3 pp 179ndash199 2013

[17] S Durmaz and O Okay ldquoAcrylamide2-acrylamido-2-methylpropane sulfonic acid sodium salt-based hydrogelssynthesis and characterizationrdquo Polymer vol 41 no 10 pp3693ndash3704 2000

[18] ISTA International Rules for Seed Testing International SeedTesting Association Bassersdorf Switzerland 2010

[19] J Hu Z Y ZhuW J Song J CWang andWMHu ldquoEffects ofsand priming on germination and field performance in direct-sown rice (Oryza sativa L)rdquo Seed Science and Technology vol33 no 1 pp 243ndash248 2005

[20] C F Zhang J Hu J Lou Y Zhang andW M Hu ldquoSand prim-ing in relation to physiological changes in seed germinationand seedling growth of waxy maize under high-salt stressrdquo SeedScience and Technology vol 35 no 3 pp 733ndash738 2007

[21] S Xu J Hu Y Li W Ma Y Zheng and S Zhu ldquoChillingtolerance in Nicotiana tabacum induced by seed priming withputrescinerdquoPlant Growth Regulation vol 63 no 3 pp 279ndash2902011


[22] K Nalampang N Suebsanit C Witthayaprapakorn and RMolloy ldquoDesign and preparation of AMPS-based hydrogels forbiomedical use as wound dressingsrdquo Chiang Mai Journal ofScience vol 34 no 2 pp 183ndash189 2007

[23] O Okay and S Durmaz ldquoCharge density dependence of elasticmodulus of strong polyelectrolyte hydrogelsrdquo Polymer vol 43no 4 pp 1215ndash1221 2001

[24] Z Wang Research on Seed Coating of Four Pasture Seeds JilinUniversity 2006

[25] H W Chen S T Jiang J Q Zhou Y Y Zhao and J HWang ldquoSuper absorbent polymer seed coating and its effect onphysiological features of corn seedrdquo Journal of Hefei Universityof Technology (Natural Science) vol 27 no 3 pp 242ndash246 2004

[26] C J Cai S N Chen M Yin H C Zhou and Q WangldquoEffects of salicylic acid on some enzyme activities related tostress resistance and content ofMDA inVanilla planifoliardquoActaBotanica Yunnanica vol 25 no 6 pp 700ndash704 2003

[27] Y Liu J J Xie and X Y Zhang ldquoSynthesis and someproperties of the copolymer of acrylamide with 2-acrylamido-2-methylpropane sulfonic acidrdquo Journal of Applied PolymerScience vol 90 no 13 pp 3481ndash3487 2003

[28] J Lin J L Ke H Z Liu and W J Hu ldquoEffects of superwater absorbent resin on the physical properties of eroded soilrdquoJournal of Fujian Agricultural and Forestry University (NaturalScience Edition) vol 31 no 2 pp 259ndash265 2002

[29] G J Geng G S Bai S N Du J Yu andM Li ldquoEffects of superabsorbent with different application methods on soil moisturesoil salinity and Lycopersicon esculentum growthrdquo Science ofSoil and Water Conservation vol 9 no 3 pp 65ndash70 2011

[30] W Q Su L Yang and D M Yang ldquoEffects of super waterabsorbent on soil improvementrdquo Journal of Northeast ForestryUniversity vol 32 no 5 pp 35ndash41 2004

Submit your manuscripts athttpwwwhindawicom

Nutrition and Metabolism

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Food ScienceInternational Journal of

Agronomy


International Journal of



Microbiology

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

AgricultureAdvances in


PsycheHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BiodiversityInternational Journal of


ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GenomicsInternational Journal of


Plant GenomicsInternational Journal of


Biotechnology Research International


Forestry ResearchInternational Journal of


Journal of BotanyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EcologyInternational Journal of


Veterinary Medicine International


Cell BiologyInternational Journal of


Evolutionary BiologyInternational Journal of



chemical industry medical health environment governanceand other fields [8 9]

2-acrylamide-2-methyl propane sulfonic acid (AMPS) isa kind of multifunctional water-soluble anionic monomerDue to the molecular structure of unsaturated double bondvinyl and the sulfonic acid functional groupwith strong anionand hydrophily AMPS has good performance of polymer-ization [10] and the water absorption ratio of its polymersit is known as a superabsorbent resin and can amount thethousands times of its own dry weight in general The AMPSmonomer has been widely applied in the synthesis of watertreatment agents adsorption and separation materials andwater absorbing and retention materials in high efficiency[10] However at present the information on the applicationof the AMPS monomer on pelleting seeds is lacking inliterature

Salicylic acid (SA) is widely regarded as an endogenousplant growth regulator which plays a significant role in thesignal transduction pathway of abiotic stresses in plants [11]Exogenous SA-induced enhancement in the resistance todrought have been observed in many plants such as maize[12] wheat [13] and rice [14] In a study soybean seedssoaking in salicylic acid caused a positive effect on theaccumulation of some ions and antagonists or modifyingthe inhibitory effect of drought stress [15] Sharafizad et al[16] found that wheat seed soaking treatment with SA in lowconcentration at low level of drought stress could decrease thegermination time and increase the germination percentageHowever the effect of SA loaded in superabsorbent polymerson plant drought resistance has not been reported

The poly(2-acrylamide-2-methyl propane sulfonic acid)(PAMPS) hydrogel was prepared and its synthetic formulawas optimized in this study Owing to high water absorbabil-ity and unique three-dimensional network structure PAMPShydrogel is considered as a controlled release material bycontrolling the release of SA from coating agent and furtherimproves the seedling drought tolerance Therefore PAMPShydrogel was used in this study to determine the performanceof superabsorbent resin and SA was used as a drought-resistant chemical that was embedded into PAMPS resinThen the enhanced drought-resistant effect of the SA-loadedPAMPS hydrogel as coating agent was studied

2 Materials and Methods

21 Materials Tobacco seeds of ldquoHonghua Dajinyuanrdquo(HHDJY) and ldquoMSk326rdquo coating agent (talc and ben-tonite) and the adhesive were provided by Yunnan Provin-cial Academy of Tobacco Agricultural Sciences China 2-Acrylamido-2-methylpropane sulfonic acid (AMPS-H+) andsalicylic acid (SA) were purchased from Shanghai Wing Sci-ence and Technology Co Ltd Shanghai China Potassiumpersulfate (KPS) N N1015840-methylene-bis(acrylamide) (MBA)NaCl and NaOH were obtained from Shanghai DingguoBiotechnology Co Ltd Shanghai China All chemicals wereused as received and experiments were carried out applyingdouble distilled water (ddH

2O)

Table 1 Preparation of poly(2-acrylamido-2-methylpropane sul-fonic acid) (PAMPS) hydrogels

Sample code AMPSlowast (g) KPS (g) MBA (g)F1 35 0007 00105F2 35 0007 00350F3 35 0007 01050F4 35 0014 00105F5 35 0014 00350F6 35 0014 01050F7 35 0021 00105F8 35 0021 00350F9 35 0021 01050lowastAMPS is 2-acrylamido-2-methylpropane sulfonic acid KPS is potassiumpersulfate MBA is N N1015840-methylene-bis(acrylamide)

22 The Synthesis of PAMPS

221 The Preparation of Stock Solution AMPS-H+ wascrystallized from boiling methanol [17] 2-Acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na+) stocksolution was prepared by dissolving 35 g of AMPS-H+ in70mL of ddH

2O followed by addition of 15mL 30 wv

NaOH solution under cooling conditions Afterwards thesolution was neutralized by titration with 1M NaOH to pH700 Finally the volume of the solution was adjusted to100mL with ddH

2O

MBA was crystallized from warm acetone The MBAstock solution was prepared by dissolving 105 g of MBA inabout 90mL of ddH

2O and then adjusting the final volume

to 100mL with ddH2O (the concentration is 0105 gmL)

KPS stock solution was prepared by dissolving 0070 g ofKPS in 10mL of ddH

2O (the concentration is 0007 gmL)

For the hydrogel synthesis ddH2O was cooled under

nitrogen bubbling

222 Synthesis of Hydrogel The copolymerization of PAMPShydrogel was carried out in ddH

2O at 40∘C in the presence

of KPS as the initiator (Table 1) AMPS MBA and KPSstock solutions were mixed together according to the ratiosin Table 1 After bubbling nitrogen for 20min the glasstubes were sealed and immersed in 55∘C water bath andthe polymerization was conductedThe hydrogel would formwell after 6sim7 h

23 The Characteristics of the Hydrogel

231 Fourier Transform Infrared Spectroscopy AnalysisFourier transform infrared spectroscopy (FTIR) was used tocharacterize the presence of specific chemical groups in thematerials 001 g of PAMPS powder was ground along withKBr to form a disc and analyzed by using FTIR absorbancemode FTIR spectra were obtained in the range of wavenumber from 4000 to 500 cmminus1 (Nicolet 5700 ThermoNicolet USA)The FTIR spectra were normalized and majorvibration bands were associated with chemical groups












119898

0)119898


0and119898









119889119898


0and119898

119889are initial








((119898

0minus 119898

119889)119898


0and 119898

119889are








00

02

04

06

08

10

12

500 1000 1500 2000 2500 3000 3500 4000

Abso

rban

ce 6269

1043712206

14546

1551716563 34436





3 Results









4 Discussions



fg

cd

fg

b

e

g

a

f0

1000

2000

3000

4000

5000W

eigh

t sw

ellin

g ra

tio (

)

Wei

ght s

wel

ling

ratio

()

Water

e

a

c

e

a

d

e

b

e0

100

200

300

400

500


NaCl solution

F1 F2 F3 F4 F5 F6 F7 F8 F9


0

1000

2000

3000

4000

5000

0 30 60 90 120 150 180 210 240

Wei

ght s

wel

ling

ratio

()

Wei

ght s

wel

ling

ratio

()

Water

0

100

200

300

400

500

0 30 60 90 120 150 180 210 240Time (min)Time (min)

NaCl solution















0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater


80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()





0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)









5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014



































119898

0)119898


0and119898









119889119898


0and119898

119889are initial








((119898

0minus 119898

119889)119898


0and 119898

119889are








00

02

04

06

08

10

12

500 1000 1500 2000 2500 3000 3500 4000

Abso

rban

ce 6269

1043712206

14546

1551716563 34436





3 Results









4 Discussions



fg

cd

fg

b

e

g

a

f0

1000

2000

3000

4000

5000W

eigh

t sw

ellin

g ra

tio (

)

Wei

ght s

wel

ling

ratio

()

Water

e

a

c

e

a

d

e

b

e0

100

200

300

400

500


NaCl solution

F1 F2 F3 F4 F5 F6 F7 F8 F9


0

1000

2000

3000

4000

5000

0 30 60 90 120 150 180 210 240

Wei

ght s

wel

ling

ratio

()

Wei

ght s

wel

ling

ratio

()

Water

0

100

200

300

400

500

0 30 60 90 120 150 180 210 240Time (min)Time (min)

NaCl solution















0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater


80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()





0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)









5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014

























00

02

04

06

08

10

12

500 1000 1500 2000 2500 3000 3500 4000

Abso

rban

ce 6269

1043712206

14546

1551716563 34436





3 Results









4 Discussions



fg

cd

fg

b

e

g

a

f0

1000

2000

3000

4000

5000W

eigh

t sw

ellin

g ra

tio (

)

Wei

ght s

wel

ling

ratio

()

Water

e

a

c

e

a

d

e

b

e0

100

200

300

400

500


NaCl solution

F1 F2 F3 F4 F5 F6 F7 F8 F9


0

1000

2000

3000

4000

5000

0 30 60 90 120 150 180 210 240

Wei

ght s

wel

ling

ratio

()

Wei

ght s

wel

ling

ratio

()

Water

0

100

200

300

400

500

0 30 60 90 120 150 180 210 240Time (min)Time (min)

NaCl solution















0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater


80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()





0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)









5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014

























fg

cd

fg

b

e

g

a

f0

1000

2000

3000

4000

5000W

eigh

t sw

ellin

g ra

tio (

)

Wei

ght s

wel

ling

ratio

()

Water

e

a

c

e

a

d

e

b

e0

100

200

300

400

500


NaCl solution

F1 F2 F3 F4 F5 F6 F7 F8 F9


0

1000

2000

3000

4000

5000

0 30 60 90 120 150 180 210 240

Wei

ght s

wel

ling

ratio

()

Wei

ght s

wel

ling

ratio

()

Water

0

100

200

300

400

500

0 30 60 90 120 150 180 210 240Time (min)Time (min)

NaCl solution















0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater


80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()





0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)









5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014


































0

20

40

60

80

100

0 5 10 15 20 25 30 35 40

Wat

er re

tent

ion

ratio

()

Time (d)PAMPSWater


80

84

88

92

96

100

30 50 70 90 110

Wat

er re

tent

ion

ratio

()





0

5

10

15

20

25

30

35

40

10 20 30 40 50 60

PAM

PS d

egra

datio

n ra

tio (

)









5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014


























5 Conclusions






Acknowledgments


References


































Journal of




Agronomy





Microbiology




Volume 2014




































Journal of




Agronomy





Microbiology




Volume 2014
























research article an enhanced drought-tolerant...

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