A review on Air Pollution Tolerance Index ( APTI ) and Anticipated Performance Index ( API )

Now a day’s air pollution is one of the serious problems around the world. Plants can filter the air via-aerial elements particularly through twigs, stems, leaves, etc. Afforestation program is the best way to control the air pollution. Air pollution tolerance index(APTI) is an intrinsic quality of trees to control pollution problems, which is currently of major concern of urban localities.The trees having higher tolerance index rate are tolerant towards air pollution and can be used as a source to control air pollution, whereas the trees having less tolerance index can be used asan indicator to know the rate of air pollution.By combining biochemical and aggregate factors the Anticipated Performance Index is prepared, which is also helpful in green belt development. The present review is based on the assessment of APTI and API potential of different plants for mitigating air pollution. Current world Environment Journal Website: www.cwejournal.org ISSN: 0973-4929, Vol. 13, No. (1) 2018, Pg. 55-65 COnTACT R. K. Aggarwal rajeev1792@rediffmail.com Department of Environmental Science, YSP University of Horticulture & amp; Forestry, Nauni, Solan, H. P,173230 India. © 2018 The Author(s). Published by Enviro Research Publishers This is an Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted NonCommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. To link to this article: http://dx.doi.org/10.12944/CWE.13.1.06 Article history Received: 13 October 2017 Accepted: 24 February 2018


Introduction
Due to industrialization and urbanization, air pollution has turn out to be a serious problem.Now a day's particulate matter is the big concern due to their undesirable impact on plant and animal 1 .The recognition and classification of plants into tolerant and sensitive groups is essential because the sensitive plants can use as an indicator and the tolerant as a sink for the pollutants in city and developed habitats 2 .Plants have a very close relationship with nature and if any altered condition occurs in the atmosphere, it directly affects the physiology and biochemistry of plant.Vegetation works as a sink for air pollution and reduce pollution level in the atmosphere 3 .Most plants experience internal changes before showing noticeable injure to leaves when they are open to air pollutants 4 .Hence, this review was conducted to assess the biochemical changes and its role in air pollution tolerance index, a major factor that gives sensitivity, tolerance to plants.PANDA et al., Curr.World Environ., Vol.13(1) 55-65 (2018)   Air pollution tolerance index indicate the potential of vegetation to encounter air pollution 5 .Plants naturally pure the air by consuming particulate matter and smoke.Sensitive tree species are suggested as bio-indicators 6 .Vegetation shows dissimilar behaviour for various pollutants and all components of tree can be used as bio-monitors 7 .They are very significant for decisive and balancing ecology by nutrient cycling and gases.Directly and indirectly air pollution can affect plants by leaves and through soil acidification 8,9 .Several researchers agree that air pollutants affect plant growth adversely 10,11 .Plants preliminarily accept air pollution thus, performs like a scavenger for pollutants 12 .As the trees are being continuously exposed to the environment, hence they attract, gather and combine pollutants impinging on their leaf surface; therefore they show noticeable or slight changes depending on their sensitivity level 13 .Physiological changes take place in plants when open to air pollutants before showing visible damage to the foliage 14 .Even leaves can act as natural filters that can eradicate great number of air borne pollutants and consequently recover the quality of air in polluted atmosphere 15 .On the other hand, this function of pollution abatement can be best performed by the pollution tolerant type 16 .Thus, air pollution tolerance index (APTI) is used to choose tolerant species and helps in monitoring plant tolerance towards air pollution.So assessment of plants on the basis of their level of tolerance to air pollution is essential.Consequently, APTI based on biochemical parameter is generally employed for recognising the tolerance level of plants.

L e a f B i o c h e m i c a l A n d P h y s i o l o g i c a l Parameters
The tolerance level of different plants mainly depends upon the morphological and physiological characters.Various type of biotic, abiotic and physical factors control plants life, including temperature, humidity, soil chemistry, pH, oxygen levels and salinity.Plant species with high amount of ascorbic acid are considered to be tolerant to air pollutants.Chlorophyll is known as an important stress metabolites and higher chlorophyll content in plants might favour tolerance to pollutants.The character of plants changes location wise depending upon various environmental factors, so different species exhibit different tolerability in different places.Studies showed that in the polluted sites the tree leaves turned in to smaller size and the stomata also changes.
To work out API, socio-economic importance of the plants growing alongside the roads is studied through field survey and from the available literature.In order to study socio-economic importance, characters like plant habit, canopy structure etcis considered.By combining the biological and socio-economic characters like plant habit, canopy structure, type of plant, laminar structure and economic value mentioned above and resultant APTI is worked out, The API is calculated for the selected species.Based on these characters certain grades (positive or negative) are allotted to plants and are scored according to their grades.The gradation of plant species based on APTI as well as biological parameters and socio-economic importance has been presented in Table 1 and Table 2. and Prosopis having lowest (4.57).Ziziphus was selected as the plant susceptible to air pollution in this study.In addition, the results of assessment of the above mentioned index showed that plants with higher APTI can be used as reducers of pollution and plants with lower APTI can be used to measure air pollution.In Indore city (MP) Patidar et al., 37 studied the impact of vehicular pollution on the plants growing along the A.B road.The study was done by selecting five heavily polluted sites of the Agra-Bombay highway (NH-3).Thevetianeriifolia, Magniferaindica, Psidiumguajava plants were selected due to their abundance in that road.Proline and Chlorophyll content are analyzed.They found that at most of the sites chlorophyll content was decreased in the foliage of the studied vegetation as compared with the plants of reference site while proline content was increased when compared with the reference site.Results of the current study shown that chlorophyll contents in all the vegetation varied with the pollution status of the site i.e.chlorophyll content of foliage decreases in the highly polluted area.It was concluded that these parameters are highly significant in understanding the plantenvironment interactions and are used for developing of bio-indicator groups.Ogunrotimi et al., 38 evaluated the sensitivity and tolerance levels of the 12 tree species from 3 major roads to airpollution using APTI and results showed that the APTI of the tree species ranged between 9.   48 to assess the anticipated performance index of plants growing alongside the National Highway 21 revealed that comparison of the grading parameters by their summation for the API showed a variation in the plant species from a very poor to very good scale.Among the four plant species selected Toonaciliata with highest API was in the very good category followed by Ficuscarica and Meliaazediractain the poor and Morusalba under the very poor category.Toonaciliata was the most tolerant species among the selected plants and also this species has the high economic and aesthetic value.The study further signifies that Toonaciliata can be recommended for plantation in the polluted areas.The study concluded that all the biochemical, physiological, biological as well as socio-economic parameters of the plant species play an important role in determining the sensitivity and tolerance of plants to air pollution.The data related to total chlorophyll content, Ascorbic acid content, Relative water content, pH of leaf extract and APTI have been summarised in Table -

Conclusion
The extensive review has focussed on the measurement and monitoring of APTI and API of plant species growing alongside the Roads and industrial areas.These are useful tools to assess the tolerance level of plant species towards air pollution.The tolerant plant species can be used as pollution sink and help in controlling and mitigating the adverse impacts from air pollution.Plants having high APTI and API value are selected for the green belt improvement and helpful in long term air pollution management in city and developed areas.On the basis of review many plant species are found to be tolerant towards air pollution and are suitable for planting around industrial area and roadsides.

Table 2 : Rating used for Anticipated Performance Index of plant species grade score Assessment category
34cusrumphii, Azadirachtaindica and Greweliarobusta(35.7,30.5, 34.3) are less tolerant.Alstoniascholaris, Cassia simea and Bauhinia variegata(21.5,6.09,18.22)aresusceptiblespecies.Begum et al.,21examined the air pollution tolerance index of various tree species around different manufacturing areas of Bangalore city.Seventeen plant species were selected for evaluation and out of these Syzygiumcumini showed highest APTI value which is 16.1, 32, and 35 in three different industrial areas and considered as tolerant species followed by Azadirachtaindica and Madhucalatifolia Roxb.Gupta et al.,22evaluated the APTI of various plant species in Burdwan Babu et al.,27evaluated the From two sites, where one site is polluted area of a cement industry and another site is Yogi Vemana University campus.Ten samples were collected from each sites and analysed.In the polluted site APTI values were in the range of (7.38-10.12)and in the control site is Madan et al.,32determined APTI and API of Ashok (Polyalthialongifolia), Peepal PANDA et al., Curr.World Environ., Vol.13(1) 55-65 (2018) for evaluation of air pollution tolerance index around Rohtak City.Out of the 15 tree species F.virens and E. Oblique were selected for green belt development.Muhammed Aji et al.,34selected three different sites for evaluation of APTI in Maiduguri.6plantspecies were selected on the basics of their abundance.The study showed that Mangiferaindica having highest APTI value which is (30.02) and Cassia angustifolia having lowest(14.24).
24nsitive one.Sulistijorini et al.,19selected eight plant species from polluted Jagorawi highway and unpolluted site of Sindangbarang field in Indonesia.Various physiological parameters of the trees were recorded.Lagerstroemia speciosa was found more tolerant towards air pollution, Pterocarpusindicus, Delonixregia, Swieteniamacrophylla were less tolerant and Cinnamomumburmanii is sensitive towords air pollution.Tripathi et al.,20evaluated the APTI of selected plant species growing alongside Moradabad city and Found that Holopteleaintegrifolia, Saracaindica and Pithecolobiumdulcis having highest APTI value i.e 55.8, 52.0 and 34.8 considered as tolerant species.town,WestBengal.Ashok-Saracaindica, Debdaru-Polyanthialongifolia, Banyan-Ficusbenghalensis, Dumur-Ficushispida, Guava-Psidiumguajava, Sisoo-Dalbergiasisoo, Mango-Mangiferaindica, Chattim-Alstoniascholaris, Mahagunii-Swieteniamahoganii, Asattha-Ficusreligiosa were selected for evaluation and found that Banyan, Mango, Mahagunii and Asoke having highest API value.Tripathi et al.,23also studied the APTI of plants commonly growing around the industrial area of Varanasi.APTI was calculated by testing various parameters and API was calculated based on resultant APTI, biological and other socio economic characteristics of plants.Out of these plants Ficusinfectoria and Ficusreligiosa considered as tolerant species.Depalakshmi et al.,24evaluated APTI of different plant species growing around the Bangalore city.Ten commonly growing plant species were selected and fresh leaf samples of these plants were collected and analysed.Bougainvillea spectabilis and Ageratum conyzoides are considered as more susceptible type, while Ficusreligiosa, Bambusabambos and Terminaliacatappa with reasonable changes are regarded as tolerant type.W h i l e P e l t o p h o r u m p t e r o c a r p u ma n d (6.44-9.6).Out of the ten sample Aeglemarmelos having highest APTI values and Ziziphuszizyphus having lowest APTI values.Wang et al., 28 investigated the Leaf dust holding qualities of three tree species growing around the campus of Xi'an University of Architecture & Technology located in the south of Xi'an.S. japonica, P. acerifolia and C. deodara were selected and found that P. acerifolia having highest particulate matter holding capacity. Baiyaraj et al., 29 .Studied the air pollution tolerance index of 11 plant species growing alongside the industrial area of Neyveli town of Tamil Nadu.Out of these eleven plant species Eucalyptus sp having highest APTI value (6.52 ) and Murryakoenigii showed lowest (0.81).Nwadinigwe 30 evaluated the air pollution tolerance index of six plant species around the urban area of Nigeria.Anacrdiumoccidentale, Bougainvillea s p e c t a b i l i s M a n g i fe ra i n d i c a , D e l o n i x r e g i a , Ixoracoccinea, and Durantaerecta were selected and out of these six plant species Delonixregia gave Khayasenegalensis, Eucalyptus spp a n d Azadiractaindica are moderate species (28.61, 24.10 and 28.23).Akilan et al., 35 studied APTI values of the four selected species viz, Tamarindusindicus (Tamarind), Neerium oleander(Oleander),

Table 3 : Biochemical parameters along with APTI of plant species Author and Location Year Plant species (vegetation) (Air Pollution Tolrance Index)
47cusinfectoria, Mangiferaindica and Ficusreligiosa were classified under the 'excellent' category.Mondal et al.,44determined the Air pollution Tolerence Index(APTI) of ten plant species collected from Burdwan town, West Bengal.High value of APTI was found in Pisidiumguajava which is 31.75% and lowest APTI found in Ficushispida which is 13.26%.The API was also calculated by considering the APTI and other parameters.On the basis of API Banyan, Mango, Mahagunii and Asoke were suitable for green belt development.Chavan et al.,45evaluated the API of different plants growing around the Aurangabad city and found that Azadirachataindica and Mangiferaindica were the tree species having good API value because of their biochemical and socioeconomic characters while Polyalthialongifolia and Dalbergiasissoo were having moderate and poor API value respectively.Esfahani et al.,46evaluated the anticipated performance index of various plant species in green belt of Isfahan, Iran.Tolerant plant species to air pollution were identified on the basis of their API values.Study showed that air pollution tolerance index in identifying resistant species to air pollution is more appropriate than anticipated performance index in semiarid areas like Isafahan.It has been noted that API is beneficial too, when it is calibrated for arid and semiarid areas.Ogunkunle et al.,47calculated API of four plant species growing alongside the University of 49Based upon API, Gupta et al have identified the Arjun and Morus plant species as very good performers out of four plant species viz.Arjun, Morus, Sheesham and Ashok at Delhi49.Hence, these workers have suggested Arjun and Morus plants can be used for the greenbelt development purpose in the Delhi region.Their study included the dustfall deposition on the foliar in Delhi region.The APTI values of their study suggested that all the four species were sensitive and can be used as biological indicators.