Embed Size (px)
Citation preview
lable at ScienceDirect
Journal of Environmental Management 95 (2012) S19eS24
Contents lists avai
Journal of Environmental Management
journal homepage: www.elsevier .com/locate/ jenvman
Evaluating the response of two high yielding Indian rice cultivars against ambientand elevated levels of ozone by using open top chambers
Abhijit Sarkar, S.B. Agrawal*
Laboratory of Air Pollution and Global Climate Change, Ecology Research Circle, Department of Botany, Banaras Hindu University, Varanasi 221005, India
a r t i c l e i n f o
Article history:Received 29 September 2009Received in revised form16 June 2011Accepted 24 June 2011Available online 23 July 2011
Keywords:Ozone pollutionIndian riceOpen top chamberGrowthYieldProteome analysis
* Corresponding author. Tel.: þ91 542 2368156; faxE-mail addresses: [email protected],
(S.B. Agrawal).
0301-4797/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.jenvman.2011.06.049
a b s t r a c t
A continuous increase in the background level of tropospheric ozone (O3) has become a major challengefor present and future agricultural productivity at worldwide. Present study was designed to assess theimpact of ambient (present) and elevated (future) concentrations of O3 on two cultivars of Indian rice(Oryza sativa L. cvs Malviya dhan 36 and Shivani). Shoot and root lengths, number of leaves and total leafarea were severely affected by both ambient and elevated concentrations of O3. Photosynthetic rate,stomatal conductance and photosynthetic efficiency (Fv/Fm) were also reduced by O3 with more drasticeffects under elevated levels of O3. Leaf proteome showed reduction of some major proteins due to O3.Pollen viability, viable florets plant�1 and economic yield also showed significant negative impact underO3-exposure in both the test cultivars. The experimental findings depict that both the cultivars of ricedemonstrate differential response against O3, and it may help the plant breeders in selection of resistantcultivars for the area having higher concentrations of O3.
� 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Tropospheric ozone (O3) has long been recognized as a majorthreat to global agriculture (Booker et al., 2009; Cho et al., 2011). Thissecondary air pollutant is normally produced by photochemicalreactions, involvingvolatile organic compoundsandnitrogenoxides(NOx), under bright sun light. According to Vingarzan (2004), themean global concentrations of tropospheric O3 will rise by 0.5e2%annually; unless the levels of primary pollutants are reduced.
Rice is cultivated in around 95 countries at worldwide; andprovides food for more than 50% of global population (IRRI, 2002).Yonekura et al. (2005) reported that the yield of Japanese rice isreduced by 5e10% under ambient O3-exposure; and this loss mightincrease up to 25e35% by 2050. Ainsworth (2008) calculated 14%yield loss in rice, exposed to 62 ppb of O3, in a meta-analysis of 12peer-reviewed studies published between 1980 and 2007.Researchers have also found that, not only yield but other majorgrowth parameters in plants were severely affected by O3 too(Ainsworth, 2008; Rai and Agrawal, 2008; Sarkar and Agrawal,2010a). Rai and Agrawal (2008) observed significant reductions inphotosynthetic rate, stomatal conductance and total chlorophyll;which resulted in 11e15% yield loss in two cultivars of Indian rice
: þ91 542 [email protected]
All rights reserved.
under ambient O3-exposure at Varanasi, India. Singh et al. (2005)have also reported major loss in total biomass of Beta vulgaris L.plants under ambient O3 concentrations in Allahabad, India.Recently, Sawada and Kohno (2010) have noticed dose dependentyield reduction in 12 Indian and Japanese cultivars of rice underelevated O3-exposure. Plant reproductive parameters, viz. flowers,pollen viability, fruit set, etc., also respond poorly under O3-expo-sure (Ollerenshaw and Lyons, 1999; Black et al., 2000; Sarkar andAgrawal, 2010a). Some researchers reported that O3 causes severedamage in plant proteome too, by inhibiting the expression ofseveral photosynthetic and primary metabolism related proteins;and indicated this as amajor cause behind the reduced productivityin crop plants under O3-exposure (Cho et al., 2008; Sarkar andAgrawal, 2010b; Sarkar et al., 2010).
Keeping the above points in mind, this investigation wasdesigned to evaluate the impact of O3 on two Indian rice cultivarsby assessing certain growth, reproductive, physiological, molecularand yield parameters. The findings might help in screening of ricecultivars for the area experiencing high concentrations of O3.
2. Materials and methods
2.1. Rice cultivation at experimental site
Theexperimentwascarriedout at theAgricultural ResearchFarm,Banaras Hindu University, India. The site (25� 140 N, 82� 030 E) was
A. Sarkar, S.B. Agrawal / Journal of Environmental Management 95 (2012) S19eS24S20
located at 76.1 m above mean sea level. Soil of the study site wastypical sandy loamwith pH 7.2. Two high yielding cultivars of Indianrice (Oryza sativa L. cultivars Malviya dhan 36 and Shivani) wereselected for the experiment. At the age of 21 days, seedlings weretransplanted in different experimental setups. Recommended doseof fertilizers (120, 60 and 60 kg ha�1 N, P and K as urea, single superphosphate andmuriateofpotash, respectively)wereused forpresentstudy.
2.2. Ozone monitoring at experimental site
Ozone monitoring was done on a 12 h day�1 basis(6:00e18:00 h) at the experimental site and its concentrationswere measured by using automatic O3-analyzer (Model APOA 370,HORIBA Ltd., Japan).
2.3. Experimental design
Rice plants were exposed to two elevated levels of O3 by usingopen top chambers (OTCs) as performed by Sarkar and Agrawal(2010a). Experimental OTCs were divided as: charcoal filtered air(FC), non e filtered air (NFC), non e filtered air þ 10 ppb O3 (NFCþ)and non e filtered airþ 20 ppb O3 (NFCþþ). By this design, the riceplants were exposed to four different levels of O3: (i) nearly no O3 inFC, (ii) ambient level of O3 in NFC, (iii) ambient þ 10 ppb O3 inNFCþ, and (iv) ambient þ 20 ppb O3 in NFCþþ. Open plots (OPs,n ¼ 3) were also maintained to monitor the effects of chamberenclosures. The treatments were performed in a complete
Shoo
t le
ngth
(cm
)
0
20
40
60
80
100
120
140
160
Num
ber
of le
aves
0
10
20
30
40
FC OP NFC
25 DAT 50 DAT 2TAD57
Malviya dhan 36 Shivani
25 DAT 50 DAT 75 DAT
a abccd
a b
ccd
ab bc
d
a aabab c
a bcc
d
abb
cd
a
a
c
bcbc b
a
aa
aa
bcc d
bb
c d bbb
c
b
ccd b
bc
d
a
Fig. 1. Effect of O3 on shoot height, root length, number of leaves and leaf area of two diffdifferent letters indicate significant differences among each group of bars according to Dun
randomized manner. O3-exposure was done by O3 generators(Model Systrocom, India) daily at the peak O3 period (from 10:00 hto 15:00 h) of local time.
2.4. Growth response analysis
To determine various growth and biomass parameters, fivemonoliths (10� 10� 20 cm3) containing intact roots were carefullycollected at random from each chamber and also from open plots at25, 50 and 75 days after transplant (DAT). Growth parameters likeroot and shoot length, leaf area and number of leaves were recor-ded. Leaf area was measured using portable leaf area meter (ModelLI e 3100, LI e COR, Inc. USA).
2.5. Reproductive response analysis
Fertile florets plant�1 and pollen viability were assessed asreproductive parameters. For counting of fertile florets, the taggedspikelets were periodically evaluated until the seed set; and pollenviability was scored with 2% aceto-carmine solution as describedearlier by Sarkar and Agrawal (2010a).
2.6. Photosynthetic pigment and photosynthetic efficiency analysis
Total chlorophyll andcarotenoidsweremeasuredaccording to themethods given by Machlachlan and Zalik (1963) and Duxbury andYentsch (1956). Chlorophyll fluorescence was measured by usingportable Plant Efficiency Analyzer (Model MK2 9414, Hansatech
Leaf area (cm
2)
0
200
400
600
800
Root length (cm
)
0
2
4
6
8
10
12
14
16 NFC+ NFC++
TAD05TAD5 75 DAT 25 DAT 50 DAT 75 DAT
Malviya dhan 36 Shivani
b
a
a
a
bcbc
c
bbc
bc
d
bcc
d
bc c d
ab
c cd
a
bb
c
d
bbabc
a
a
abbb
c
bccd
bb
c
d
a
ab
c c
d b bc
d
erent rice cultivars at different stages of growth. Values are mean � SE. Bars showingcan’s test at p < 0.05.
A. Sarkar, S.B. Agrawal / Journal of Environmental Management 95 (2012) S19eS24 S21
Instrument Ltd., UK). Initial fluorescence (Fo) and maximum fluo-rescence (Fm)weremeasured tofindvariablefluorescence (Fv) andFv/Fm ratio. Photosynthetic rate (Ps) andstomatal conductance (gs)werequantified with the help of portable photosynthetic system (ModelLI-6200, LI-COR, USA). The measurements were made on the thirdfully expandedmature leaves from the topof eachplanton cloud freedays between 08.00 and 10.00 h.
2.7. Leaf proteome analysis through 1 e DGE (one dimensional gelelectrophoresis)
Comparative analysis of leaf proteome from both O3-exposedand unexposed rice plants was performed 11.5% SDS PAGE asdescribed earlier by Sarkar et al. (2010).
Fv
/ Fm
Rat
io
0.0
0.2
0.4
0.6
0.8
0
2
4
6
8
10
12
14
16
18
Pho
tosy
nthe
tic
rate
(µ
mol
CO
2 m
-2 s
-1)
0
5
10
15
20
25
25 DAT 50 DAT 75 DAT
2
Malviya dhan 36 Shivani
25 DAT 50 DAT 75 DAT
abbb
c
a
bcc
d
a
bbcd
abcc d
a
bcc
d a
bb
cd
a
abbb
c
a
bbc
d
abb
cd
abbb
c
a
bbc
d
a
bb
c
d
aabb
c
d
bbcd
abbc
d
abbc
d
a
b bc
d
a
bbcd
Fig. 2. Effect of O3 on total chlorophyll, carotenoids, photosynthetic rate stomatal conductanmean � SE. Bars showing different letters indicate significant differences among each grou
2.8. Yield parameters
Rice plants, at maturity, were harvested to assess different yieldattributes. Ten plants from each treatment were sampled; andweight of grains m�2 and harvest index (HI) were recorded.
2.9. Statistical analysis
Observed data were subjected to one and two way analysis ofvariance (ANOVA) for assessing the significance of quantitativechanges in different parameters due to various treatment andtreatment with cultivars. Duncan’s multiple range test was per-formed as post hoc on parameters subjected to ANOVA test. The
0
1
2
3
4
5
6
5 DAT 50 DAT 75 DAT 25 DAT 50 DAT 75 DAT
Malviya dhan 36 Shivani
bbcd
abb
cd
a
bb
cd
abbbc
a
bbc
d
a
bb
cd
Stomatal conductance (m
ol H2 O
m-2 s -1)
0
1
2
3
4
FC
OP
NFC
NFC+
NFC++
a a
a aa
a
bbcd
dc
bb
bbc
dd
cbbbb
c
d
d
c
bb
ce and Fv/Fm ratio of two different rice cultivars at different stages of growth. Values arep of bars according to Duncan’s test at p < 0.05.
A. Sarkar, S.B. Agrawal / Journal of Environmental Management 95 (2012) S19eS24S22
statistical analyses were performed using SPSS software (SPSS Inc.,version 16.0).
3. Results and discussion
Present experiment was designed to evaluate the impact ofambient and elevated concentrations of O3 on two high yieldingIndian rice cultivars; on growth, photosynthetic, reproductive,molecular and yield parameters; under near natural conditionsusing OTCs. Use of activated charcoal filters in FCs reduced the O3concentration by 92.5%. During the experimental period, meanmonthly O3 concentrations were 42.7 ppb in June, 07; 41.3 ppb inJuly, 07; 44.7 ppb in August, 07; 58.2 ppb in September, 07 and59.9 ppb in October, 07.
In general, O3 severely affects the growth and development ofplants. Shi et al. (2009) reported significant reductions in plantheight and leaves in four rice cultivars under elevated O3 levels atXiaoji town, China. Sarkar and Agrawal (2010a) also found 39e62%reduction in plant height, 54e60% in total number of leaves underambient þ 20 ppm elevated O3 in two wheat cultivars at Varanasi,India. Agrawal et al. (2005) also reported significant reductions inshoot and root lengths, total leaf area and biomass of mung beanplants under ambient levels of O3 at Allahabad, India. Presentresults also followed similar trend at post O3-exposure (Fig. 1). At75 DAT; Malviya dhan 36 showed 7, 12.6 and 30%, and Shivanishowed 5.7, 17.6 and 27% reductions in shoot length at NFC, NFCþand NFCþþ, as compared to FCs, respectively (Fig. 1). Total numberof leaves was also reduced by 20, 31.5 and 36% in Malviya dhan 36;and 23, 34.8 and 44.9% in Shivani, in 75 DAT at NFC, NFCþ andNFCþþ, as compared to FCs, respectively (Fig. 1). Other growthparameters like root length and total leaf area also reduced simi-larly at post O3-fumigation (Fig.1). Miller et al. (1999), in their study
Pol
len
viab
ility
(%
)
0
20
40
60
80
100
120
Malviya dhan 36 Shivani
Wei
ght
of g
rain
s (g
m -2)
0
200
400
600
800
aa
b bb b
c c
d d
a
a
b b
bb
c
c
d
O3 x cv NS
O3 ***
cv NS
O
O3 x cv *
O3 ***
cv **
FC OP N
d
Fig. 3. Effect of O3 on various reproductive and yield parameters of two different cultivadifferences among each group of bars according to Duncan’s test at p < 0.05. Results of two*p < 0.05 and NS: not significant.
with Arabidopsis, reported that O3 can induce several senescenceassociated genes (SAGs) too. In the present study the decreasingtrend in healthy leaves at post O3-exposure, might be an effect ofSAGs activity in rice; which lead to early senescence (Fig. 1).However, at lower level of elevated O3 (NFCþ), it showed hormeticeffect on both the rice cultivars by stimulating some growthparameters at the early stage (Fig. 1). Ishii et al. (2004) also foundearly induction in the growth of rice plants under O3-exposurewithlower elevation.
As an initial effect on photosynthesis, O3 initiates the destruc-tion of total chlorophyll by preventing the synthesis of this pigment(Castagna et al., 2001). Rai and Agrawal (2008) reported 23e27%reduction in total chlorophyll in rice under ambient concentrationof O3. Results of the present study also revealed reduction inchlorophyll by 18, 31 and 41% in Malviya dhan 36, and 26, 38 and44% in Shivani, at NFCs, NFCþ and NFCþþ, as compared to FCs,respectively (Fig. 2). Carotenoids also reduced significantly at postO3-exposure (Fig. 2). According to Lichtenthaler (1987), carotenoidsare important photo-protective compounds that prevent photo-oxidative damage of chlorophyll. Rai and Agrawal (2008) alsoreported a 41e44% reduction in carotenoids under ambient O3.However, Rainieri et al. (2001) suggested that any reduction inplant pigments may serve as an adaptation against O3-stress; as thereduced number of light harvesting antennae complex mayprotects PSII from further photo-inhibition.
Ainsworth (2008) and Rai and Agrawal (2008) reported reducedphotosynthetic rate (Ps) and stomatal conductance (gs) in riceunder ambient and elevated O3-exposure. Present study alsoshowed significant reduction in Ps in both the cultivars (Fig. 2).Reduction in photosynthesis at post O3-exposure can be correlatedwith the reduced amount in photosynthetic pigments too. Even,significant reduction in gs was also observed during the present
Viable florets plant -1
0
200
400
600
800
1000
1200
Malviya dhan 36 Shivani
Harvest Index
0.0
0.1
0.2
0.3
0.4
a
a
b
b
bb
c
c
d
d
a
ab
b
b
bc
cd
d
3 x cv NS
O3 ***
cv *
FC NFC+ NFC++
O3 x cv NS
O3 ***
cv NS
rs of rice. Values are mean � SE. Bars showing different letters indicate significantway ANOVA shown as O3 � cv, O3 and cv. Level of significance ***p < 0.001, **p < 0.01,
Fig. 4. 1 e DGE analysis of O3-exposed (NFCþþ) and unexposed (FC) leaf proteome oftwo Rice cultivars. (1: Protein from O3-exposed leaves of cultivar Shivani; 2: Proteinfrom unexposed leaves of cultivar Shivani; 3: Protein from O3-exposed leaves ofcultivar Malviya dhan 36; 4: Protein from unexposed leaves of cultivar Malviya dhan36). Arrows indicate the position of differential response in proteins.
A. Sarkar, S.B. Agrawal / Journal of Environmental Management 95 (2012) S19eS24 S23
study in both the cultivars under O3-exposure (Fig. 2). Fv/Fm ratioindicates toward the photochemical efficacy of PSII, and anydecrease in this ratio might serve as a reliable indication of O3-induced photo-inhibition in plants. In the present experiment, Fv/Fm decreased by 15, 18 and 27% in Malviya dhan 36, and 18, 21 and24% in Shivani at NFCs, NFCþ and NFCþþ, as compared to FCs,respectively (Fig. 2). Rai and Agrawal (2008) also found a significantreduction in Fv/Fm in rice under ambient O3-exposure.
Ozone has also been recognized as a potent inhibitor of repro-ductive structures in plants (Black et al., 2000). Schoene et al.(2004) found that O3 affected the development of pollen byinhibiting starch accumulation in pollen grains in perennialryegrass (Lolium perenne L.). Sarkar and Agrawal (2010a) alsoreported significant reduction in pollen viability and viable floretsin wheat plants under O3-exposure. In present study, pollenviability was affected by 25, 32 and 40% in Malviya dhan 36, and 16,26 and 33% in Shivani at NFCs, NFCþ and NFCþþ, as compared toFCs, respectively (Fig. 3). Viable florets also followed the similartrend of reduction. Two ways ANOVA showed that in both theparameters, O3 was the main determining factor (Fig. 3).
In any crop plant, yield is the ultimate interest of human society;and studies have shown that O3 can cause severe damage to thegrain and fruit yield of diverse crop plants (Ainsworth, 2008;Booker et al., 2009). Liu et al. (2009) showed that the relativeyield loss in rice from 1990 to 1995 was 1.1e5.8% and would reach10.8% in 2020 in Chongqing, China. Sawada and Kohno (2010) alsoreported significant yield loss under both ambient and elevatedlevels of O3-exposure in 12 rice cultivars. Present results alsoresponded similarly; as yield (g m�2) was reduced by 15, 27 and39% in Malviya dhan 36, and 13, 31 and 45% in Shivani at NFCs,NFCþ and NFCþþ, as compared to FCs, respectively (Fig. 3). Two
way ANOVA also showed that yield was significantly varied due toO3 (p < 0.001), cultivar (p < 0.01) and O3 � cultivar (p < 0.05).Harvest index (HI) reflects the partitioning of photosynthatesbetween grains and above ground biomass. Present results alsoshowed significant reductions in HI due to O3-exposure in both therice cultivars (Fig. 3).
O3-exposure also induced injuries in rice leaves, and the analysisof leaf proteome of O3-exposed and unexposed leaves showedsome definite changes at three points, i.e. at 54 kDa, 35 kDa and15.7 kDa (Fig. 4). While comparing the results with earlier studies(Cho et al., 2008; Sarkar et al., 2010), it might be concluded that thelarge subunit (LSU) and small subunits (SSU) of RuBisCO wereadversely affected with some other photosynthetic and energymetabolism proteins in both the rice cultivars at post O3-exposure.
4. Conclusion
Present study clearly depicts that ambient as well as elevatedlevels of O3 adversely affected the growth and yield of both the ricecultivars. Reductions of plant height, leaf area, total chlorophyll,photosynthetic rate, stomatal conductance, and chlorophyll fluo-rescence kinetics; increasing number of non e viable florets andpollens, and inhibition in the expression of major proteins are thefundamental manifestations of O3-stress. Yield is the major interestof human society for retaining ‘food security’, and O3 severelyaffected this parameter in both the test cultivars. However, cultivarShivani showed significantly higher reduction in yield than cultivarMalviya dhan 36 under elevated levels of O3. This clearly pointedtoward the differential cultivar response of rice against O3, andmight be used for selecting suitable cultivars for an area experi-encing higher concentrations of O3.
Acknowledgments
The authors gratefully acknowledge the receipt of financialassistance in form of a research project (Scheme number: 24/292/06/EMR-II) funded by the Council for Scientific and IndustrialResearch (CSIR), New Delhi, Government of India. Authors alsoexpress their gratefulness to Prof. María Isabel Sastre Conde,Chairperson of the 3 IMEBE for giving the opportunity to presentthe findings of this paper during the conference and also for fruitfulsuggestions for preparing this manuscript.
References
Agrawal, S.B., Singh, A., Rathore, D., 2005. Role of ethylene diurea (EDU) in assessingimpact of ozone on Vigna radiata L. plants in a suburban area of Allahabad(India). Chemosphere 61, 218e228.
Ainsworth, E.A., 2008. Rice production in a changing climate: a meta-analysis ofresponses to elevated carbon dioxide and elevated ozone concentration. GlobalChange Biology 14, 1642e1650.
Black, V.J., Black, C.R., Roberts, J.A., Stewart, C.A., 2000. Impact of ozone on thereproductive development of plants. New Phytologist 147, 421e447.
Booker, F., Muntifering, R., McGrath, M., Burkey, K., Decoteau, D., Fiscus, E.,Manning, W., Krupa, S., Chappelka, A., Grantz, D., 2009. The ozone componentof global change: potential effects on agricultural and horticultural plant yield,product quality and interactions with invasive species. Journal of IntegrativePlant Biology 51 (4), 337e351.
Castagna, A., Nali, C., Ciompi, G., Lorenzini, G., Soldatini, G.F., Ranieri, A., 2001. O3exposure effects photosynthesis of pumpkin (Cucurbita pepo) plants. NewPhytologist 152, 223e229.
Cho, K., Shibato, J., Agrawal, G.K., Jung, Y., Kubo, A., Jwa, N., Tamogami, S., Satoh, S.,Higashi, Kimura S., Saji, H., Tanaka, Y., Iwahashi, H., Masuo, Y., Rakwal, R., 2008.Integrated transcriptomics, proteomics, and Metabolomics analyses to surveyozone responses in the leaves of rice seedling. Journal of Proteome Research 7,2980e2998.
Cho, K., Tiwari, S., Agrawal, S.B., Torres, N.L., Agrawal, M., Sarkar, A., Shibato, J.,Agrawal, G.K., Kubo, A., Rakwal, R., 2011. Tropospheric ozone and plants:absorption, responses, and consequences. Reviews of Environmental Contami-nation and Toxicology 212, 61e111.
A. Sarkar, S.B. Agrawal / Journal of Environmental Management 95 (2012) S19eS24S24
Duxbury, A.C., Yentsch, C.S., 1956. Plankton pigment monographs. Journal of MarineResearch 15, 19e101.
IRRI, 2002. Rice Almanac: Source Book for the Most Important Economic Activity onEarth, third ed. CABI Publishing, Oxon, UK.
Ishii, S., Marshall, F.M., Bell, J.N.B., 2004. Physiological and morphological responsesof locally grown Malaysian Rice Cultivars ( Oryza sativa L.) to different ozoneconcentrations. Water. Air and Soil Pollution 155, 205e221.
Lichtenthaler, H.K., 1987. Chlorophylls and carotenids pigments of photosyntheticbiomembranes. Methods in Enzymology 148, 351e382.
Liu, F., Wang, X., Zhu, Y., 2009. Assessing current and future ozone-induced yieldreductions for rice and winter wheat in Chongqing and the Yangtze River Deltaof China. Environmental Pollution 157, 707e709.
Maclachlan, S., Zalik, S., 1963. Plastid structure, chlorophyll concentration and freeamino acid composition of a chlorophyll mutant of barley. Canadian Journal ofBotany 41, 1053e1062.
Miller, J.D., Arteca, R.N., Pell, E.J., 1999. Senescence-associated gene expressionduring ozone-induced leaf senescence in Arabidopsis. Plant Physiology 120,1015e1024.
Ollerenshaw, J.H., Lyons, T., 1999. Impacts of ozone on the growth and yield of field-grown winter wheat. Environmental Pollution 106, 67e72.
Rai, R., Agrawal, M., 2008. Evaluation of physiological and biochemical responses oftwo rice (Oryza sativa L.) cultivars to ambient air pollution using open topchambers at a rural site in India. Science of the Total Environment 407,679e691.
Rainieri, A., Giuntini, D., Ferraro, F., Nali, B., Baldan, G., Lorenzini, G., Soldatini, G.F.,2001. Chronic ozone fumigation induces alterations in thylakoid functionalityand composition in two poplar clones. Plant Physiology and Biochemistry 39,999e1008.
Sarkar, A., Agrawal, S.B., 2010a. Elevated ozone and two modern wheat cultivars: anassessment of dose dependent sensitivity with respect to growth, reproductiveand yield parameters. Environmental and Experimental Botany 69 (3),328e337.
Sarkar, A., Agrawal, S.B., 2010b. Identification of ozone stress in Indian rice throughfoliar injury and differential protein profile. Environmental Monitoring andAssessment 161, 205e215.
Sarkar, A., Rakwal, R., Agrawal, S.B., Shibato, J., Ogawa, Y., Yoshida, Y., Agrawal, G.K.,Agrawal, M., 2010. Investigating the impact of elevated levels of ozone ontropical wheat using integrated phenotypical, physiological, biochemical, andproteomics approaches. Journal of Proteome Research 9, 4565e4584.
Sawada, H., Kohno, Y., 2010. Differential ozone sensitivity of rice cultivars as indi-cated by visible injury and grain yield. Plant Biology. doi:10.1111/j.1438e8677.2009.00233.x.
Schoene, K., Franz, J., Masuch, G., 2004. The effect of ozone on pollen developmentin Lolium perenne L. Environmental Pollution 131, 347e354.
Shi, G., Yang, L., Wang, Y., Kobayashi, K., Zhu, J., Tang, H., Pan, S., Chen, T., Liu, G.,Wang, Y., 2009. Impact of elevated ozone concentration on yield of four Chineserice cultivars under fully open-air field conditions. Agriculture, Ecosystems andEnvironment 131, 178e184.
Singh, A., Agrawal, S.B., Rathore, D., 2005. Amelioration of Indian urban air pollutionphytotoxicity in Beta vulgaris L. by modifying NPK nutrients. EnvironmentalPollution 134, 385e395.
Vingarzan, R., 2004. A review of surface O3 background levels and trends. Atmo-spheric Environment 38, 3431e3442.
Yonekura, T., Shimada, T., Miwa, M., Arzate, A., Ogawa, K., 2005. Impacts of tropo-spheric ozone on growth and yield of rice. Journal of Agricultural Meteorology60, 1045e1048.
