Thesis Abstract

<p> </p><p>Effects of heavy metals on the Air Pollution Tolerance Indices (APTI) of five<br>medicinal plants growing within quarry site in Ishi-Agu, Ebonyi State, Nigeria<br>were studied. Following laboratory analysis of the leaves of the plants for metal<br>load and four biochemical parameters of APTI computation. The metal load was<br>determined by the Atomic Absorption spectrophotometric method, while the<br>ascorbic acid was determined by the titremetric method, leaf extract pH by the<br>electro-chemical techniques, relative water content by plant turgidity mass and<br>the total chlorophyll, by spectrophotometric method. Foliar photomicrography<br>of the leaf was also studied. Results of Plants from experimental site showed<br>changes in physical and internal structures of the leaves that lead to closure of<br>some stomata pores in test plants and damage of some epicelluler cells.<br>Quantification of phytochemical contents of the test plants showed higher<br>values than that of control which may be due to the multiplication of some<br>organic substances caused by oxidative stress, presence of inorganic subtances<br>like heavy metals and lime stone dust.The result of elemental analysis of both<br>experimental and control plants gave the range of concentration of the metals<br>in parts per million (ppm) as follows – lead ( 2.75 – 14.13 ± 0.02); Nickle<br>(0.27 – 0.54 ± 0.01) ; Cadmium ( 2.25 – 24.30 ± 0.03); Zinc (0.11- 0.03 ±<br>0.02); and Arsenic (0.10 – 0.70 ± 0.04). Control –Lead ( 0.00 – 5.52 ± 0.01);<br>Nickle (0.13 – 0.23 ± 0.01); Cadmium (0.00 – 12.00 ± 0.03); Zinc ( 0.06 – 0.10<br>± 0.03); and Arsenic (0.02 – 0.20 ± 0.02). There was slight increase of<br>v<br>Cadmium above maximum daily permissible intake in C. ferruginea, A,<br>djalonensis, and R. communis, also there is high content of Arsenic in<br>R.communis which is the cause of oxidative strees in test plants that result in<br>the elicitation of antioxidants from plants and multiplication of ascorbic acid<br>content. The values for the percentage computation of APTI in test plants are<br>V.doniana (11.03), C.ferruginea (7.62), A.djalonesis (9.94), R. communis (11.5)<br>and M. esculenta (8.60). Control pants gave V.doniana (11.86), C.ferruginea<br>(8.21), A.djalonesis (11.86), R. communis (14.39), and M. esculenta (10.21)<br>that result in reduction of Relative water content, Ph value, Total chlorophyll<br>content and Ascorbic acid content.There is relative high content of heavy<br>metals, physiological and visible changes in some sensitive test plants. Owing<br>to information gotten from the result of this research it is not recommended that<br>plants from the quarry sites be used in herbal formulation because of possible<br>metal intoxication and attenuation of their phythopotency.</p><p>&nbsp;</p> <br><p></p>

Thesis Overview

<p> </p><p>1.1 INTRODUCTION<br>Plants occupy vital position in the ecosystem because of their role as<br>primary producers.They are also the major recipients of environmental pollution<br>owing to their static disposition. While men and other animals move away from<br>the immediate vicinity of compromised environmental status, plants remain<br>relatively immobile receiving environmental pollutants within the ecosystem.<br>The effect of particulate air pollutants on vegetation have been studied always<br>before now (Manning,1971). Air Pollution Tolerance Indices (APTI) of plants<br>is an important measure to check the effect of air pollution on medicinal plants<br>and other plants generally. Nigerian as with orther developing country suffers<br>pollution burden associated with the ever increasing human population,<br>vehicular traffic, infrastractures and industries, with negative implications for<br>the sustainability of humans, animals and plants communities (Choudhury and<br>Banerjee, 2009). Since plants major systems and organs are exposed to the<br>atmosphere, any air pollution around the environments reflects on the plant<br>health making some plant show sensitivity, some show minimal or no effect<br>while some are tolerant. The plants response to air pollutant varies from species<br>to species, type of pollutant, its reacting mechanism, and duration of exposure.<br>World Health Organization (WHO, 1989) recommends that medicinal<br>plants which form the raw materials for the finished products may be checked<br>for the presence of heavy metals. This is because after collection and<br>transformation into final dosage form, the heavy metals resident in these plants<br>may find its way into human body and may inhibit or impair the normal<br>functions of central nervous system the liver, lungs, heart, kidney and brain,<br>leading to hypertension, abdominal pain, skin eruptions, intestinal cramp and<br>different types of cancers(Shad et al., 2008).<br>This work is to investigate on the effects of lime Stones dust from quarry site in<br>Obegu Amaeze village at Ishiagu, Ebonyi state, Nigeria, on some medicinal<br>plants (Vitex doniana, Anthocliestia djalonensis, Ricinus communis, Cnestis<br>Ferruginea and Manihot esculenta ). For the fact that single parameter cannot<br>provide clear picture of the pollution induced changes, different measures like<br>APTI, Phytochemical analysis, plant leaf macroscopy and microscopy, and<br>Elemental analysis were used to authenticate, compare and relate the result.<br>1.2 Quarry<br>Quarry is the process of obtaining quarrying resources, usually rocks, found on<br>or below the land surface. The difference between mining and quarrying is that<br>quarrying extracts non metallic rocks and aggregates while mining executes the<br>site for mineral deposits. Some of the stones extracted was sandstone, lime<br>stones, perlite, marble, ironstone, slate, granite, rock salt and phosphate. They<br>are cheap and always ready for conveyance to a large market and its inclination<br>and depth are below the surface. The two principal branches of the industry are<br>the so called dimension-stone and crushed-stone quarrying. In the former,<br>blocks of stone, such as marble, are extracted in different shapes and sizes for<br>different purposes. In the crushed-stone industry, granite, limestone, sandstone,<br>or basaltic rock is crushed for use principally as concrete aggregate or road<br>stone (James, 2012).<br>1.2.1 EFFECT OF QUARRY ON ENVIRONMENT<br>Quarrying carries the potential of destroying habitats and species they support.<br>Even if the habitats are not directly removed by excavation they can be<br>indirectly affected and damaged by environmental impacts such as changes in<br>ground water or surface water that cause some habitats to dry out or others to<br>become flooded. Even noise pollution can have a significant impact on some<br>species and affect their successful production . Quarries can also provide a good<br>opportunity to create new habitats or to restore existing ones. Both positive and<br>adverse societal impacts of modern manufacturing technologies have great<br>consequences on economic, health, safety and environment in general.<br>Limestone quarrying can have many effects on environment, like dirtying of the<br>environment and roads that lead to quarry. Also there are more serious<br>consequences that quarrying portrays, quarrying releases toxic mercury into the<br>air and surrounding soil and water. Even when mercury is not present in<br>significant quantities, the air and water can be polluted by the dust generated by<br>quarry activities (Vincent et al, 2012). Quarry has the ability of destroying<br>habitants and the species they depend on both directly or indirectly. Quarry<br>causes damage to the living species by causing some unfavorable changes to the<br>ground water, noises that prevent them from having sucessesfull reproduction.<br>Moreover, there is still potential for damage to the environment particularly<br>with water contamination. For example, suspended particles though<br>chemically inert, may imbalance freshwater ecosystem. (Omosanya and<br>Ajibade 2011). The green plants (machine) mostly with explosives in order to<br>extract material for processing gives rise to noise pollution, air pollution,<br>damage to biodiversity and habitat destruction.<br>1.2.2 QUARRY WASTE<br>Quarrying involves the production of significant amounts of waste. Some<br>types of quarries do not produce large amounts of permanent waste, such as<br>sand and gravel quarries, whereas others will produce significant amounts of<br>waste material such as clay and silt. The good news is that they are generally<br>inert and non-hazardous, unlike the waste from many other processes. However,<br>there is still potential for damage to the environment particularly with water<br>contamination. Plants are major components of the ecosystem, a complex<br>interaction between the biotic and abiotic entities of the environment. The<br>industry, unfortunately discharge dust that settles not only on land, plants and<br>trees but also on surface waters used for drinking and other domestic chores by<br>the community. All quarry activities produce enough waste on the process of<br>production, though some quarry do not produce large amount of waste like sand<br>and gravel while some produce permanent waste material like silt and clay<br>crushed for use principally as concrete aggregate or road stone ( Fisher, 1944).<br>Again, like many other man made activities, quarrying involves the production<br>of significant amounts of waste. For instance, lead content in water will prevent<br>plants from getting their nutrients from the soil. Also suspended particles may<br>imbalance fresh water ecosystem. Large amount of solid can lead to flooding if<br>it is dumped on flood plains. This waste has to be monitored and kept where it<br>will not affect the environment in a harsh way (Lameed, 2010).<br>1.2.3 LAND POLLUTION<br>Land pollution, is pollution of earth natural land surface by<br>industrialization, commercial, domestic and land agricultural activities. Some of<br>the factors that contribute to land pollution are; chemical and nuclear plants,<br>mining littering, deforestations, construction etc. (James, 2012).<br>1.2.4 NOISE POLLUTION<br>Unfortunately, quarrying involves several activities that generate significant<br>amounts of noise. It starts with the preparatory activities, such as establishing<br>road or rail access, compound and even mineral processing facilities.<br>The excavation of the mineral itself involves considerable noise, particularly if<br>blasting methods are used. Following this, the use of powered machinery to<br>transport the materials as well as possibly processing plants to crush and grade<br>the minerals, all contribute even more noise to the environment (Lameed, 2010).<br>Such extraction of raw materials from their natural habitats by mining, drilling,<br>harvesting and those that relate to large scale water resources development<br>projects, construction, agriculture, energy, industry and development projects,<br>considerably affect the natural environment.<br>The process of exposing the mineral to be extracted is usually done by<br>removing the top soil and other soft layers using a scraper or hydraulic<br>excavators and dump trucks. The excavations of the minerals itself will involve<br>considerable noise, particularly when blasting methods are used.<br>1.2.5 DAMAGE TO BIODIVERSITY<br>One of the biggest negative impacts of quarrying on the environment is the<br>damage to biodiversity. Biodiversity essentially refers to the range of living<br>species, including fish, insects, invertebrates, reptiles, birds, mammals, plants,<br>fungi and even micro-organisms. Biodiversity conservation is important as all<br>species are interlinked, even if this is not immediately visible or even known,<br>and our survival depends on this fine balance that exists within nature.<br>Nevertheless, with careful planning and management, it is possible to minimize<br>the effect on biodiversity. This is one of the disadvantages of quarry on the<br>environment, its negative effect on living organisms like fish, insects,<br>invertebrates, reptiles, birds, mammal, plants, fungi, and micro-organisms. and<br>1.3 POLLUTION<br>Pollution is the introduction of a contaminant into the environment. It is<br>created mostly by human actions, but can also be as a result of natural disasters.<br>Pollution has a detrimental effect on any living organism in an environment,<br>making it virtually impossible to sustain life. It is the human introduction into<br>the atmosphere of chemicals, particulate matter, biological materials that cause<br>harm to human or other living organism, or damage the environment<br>(Anonymous, 2008). The atmosphere is a complex dynamic natural gaseous<br>system that is esential to all living things. There are some substances in the<br>atmosphere which may impair the health of plants and animals. Pollutants could<br>be classified as either secondary or primary. Pollutants that are formed in the<br>atmosphere and directly pollute the air are called primary Pollutants, while<br>those that are formed in the air when primary pollutant react or interact are<br>known as secondary pollutants(Vincent, et al., 2012)<br>1.3.1 POLLUTION AND VEGETATION<br>Industrialization areas suffer pollution because of the chemical emission<br>and others like oil spillage, Noise etc. These also affect the weather of that<br>zone which leads to increase in temperature that might result to climate<br>change. Climate change has become increasingly recognized as one of the<br>greatest challenges to human and other living things on earth. Worldwide<br>changes in seasonal patterns, weather events, temperature ranges and other<br>related phenomena have all been reported and attributed to global climate<br>change. Numerous experts in a wide range of scientific disciplines have<br>warned that negative impacts of climate change will become much more<br>intense and frequent in the future particularly if environmentally destructive<br>human activities continue unabated. Like all living members of the biosphere,<br>medicinal and aromatic plants (MAPs) are not immune to the effects of climate<br>change. Climate change is causing noticeable effects on the life cycle and<br>distributions of the world’s vegetation including wild MAPs. Some MAPs are<br>endemic to geographic regions or ecosystems particularly vulnerable to climate<br>change, which could put them at risk. The possible effects on MAPS may be<br>particularly significant due to their value within traditional systems of<br>medicine and as economically useful plants. The changing temperature and<br>wind patterns associated with climate change are causing precipitation factors<br>and giving some trees and shrubs the ability to grow taller in more open areas.<br>Some production of plants secondary metabolites are influenced by multiple<br>factors including disease, competition between plants, animals grazing, light<br>exposure, soil moisture and those other factors that may mitigate the effects of<br>climate change on plants secondary metabolites (Herbal , 2009).<br>1.3.2 EFFECT OF POLLUTION ON LEAF ANATOMY<br>Developments of stomata are often considered as one of the most important<br>developments in plants evolution. By being environmentally controlled<br>gateways into the plants controlling Co2 uptake and transpiration they are<br>central determinants of photosynthesis, cooling and nutrient uptakes (Arvel,<br>2009). To be able to balance Co2 uptake and water transpiration through<br>stomatal movements is an important response to changes in the environmental<br>conditions. Low transpiration due to stomatal closure means less cooling of the<br>leaves and less uptake and transportation of nutrients. Stomatal closure occurs<br>when the guard cells surrounding the stomatal opening lose turgor pressure and<br>close the opening (Arvel, 2009). There are many signals that induce stomatal<br>closure, eg Absciscic Acid (ABA), Secondary messengers like Ca2+ and H2O2.<br>When there is an air pollution or oxidative stress in an environment, there are<br>pathwaysb that leads to stomatal closure. Hydro passive stomatal closure<br>occurs when water evaporation from the guard cells is too low to be balanced<br>by water movements into these cells. The water is reduced to the extent that<br>osmotic pressure is reduced and cell loses tugor pressure and shrink (Lucan,<br>2002).When this happens the guard cells are unable to maintain the shapes and<br>stomatal pores is covered. Active stomatal closures occur when there is<br>increase in ABA Co2 level. This activates signaling pathways leading to<br>stomatal closure. ABA is produced in the roots and leaves during water stress<br>and is transported to the guard cell by ATP binding cassette (ABC) transporters<br>that are located in the plasma membrane, but when the transporters are<br>knocked out during oxidative or water stress, the ABA uptake is low. The size<br>of the stomatal opening is regulated by the tugor pressure cell volume of the<br>guard cells. Regulation of stomatal opening is linked to transport of ions and<br>water through channel proteins across the plasma and vacuole membrane.<br>ABA induces the production of reactive oxygen species eg. H2O2 which in turn<br>acts as a trigger for low production, inhibition of membrane proton pumps and<br>Ca2+ across both the plasma and vacuole membranes. H+ AT-pase that are<br>hyperpolarizing the plasma membranes must be inhibited to induce ABA<br>mediated stomatal closure (Merlot et al., 2007).The increased ca2+ level<br>activate slow and rapid type of anion channels, generating an anions efflux<br>from the cells. The anion efflux depolarizes the membrane, which in turn<br>causes k+ channel across both the vacuole and the plasma membrane.<br>Simultaneously Ca2+ also inhibits k+ in channel. Malate is also converted to<br>starch reducing the osmotic potential and turgor pressure further (Kim and<br>Van, 2011).The plasma membrane is thus depolarized, the turgor pressure and<br>cell volume reduced, then the stomata closed.<br>Stomata must open to admit Co2 into the leaf for photosynthesis, but<br>when they open, they allow water vapour to diffuse out of the leaf .Thus,<br>stomata opens enough to support photosynthesis, but they must at the same<br>time prevent excessive water loss. This is called constrained optimization<br>problem (Michael, et al., 1997).<br>Plants grown under high relative air humidity caused by pollutants leads to the<br>malfunctioning stomata. This stomata are unable to close in response to the<br>darkness, that result in high stomatal conductance and frequent leaf drying in<br>other research done in different humidity it has also been found that the<br>number of stomata per leaf increased with development in higher soil<br>humidity. The stomatal index, the number of stomata relative to the number of<br>epidermal cells was also found to increase with soil moisture. The stomata<br>density has been found to increase in plant with decreased ABA<br>concentrations, which have increased transpiration (Atssman, et al., 2002).<br>1.4 AIR POLLUTION<br>Air pollution is one of the severe problems the world is facing today. It<br>deteriorates ecological conditions and can be defined as the fluctuation in any<br>atmospheric constituent from the value that would have existed without human<br>activity (Tripathi and Gautam, 2007). In recent past, air pollution is responsible<br>for vegetation injuring and crop yield losses. The increasing number of<br>industries and automobile vehicles are continuously adding toxic gases and<br>other substances to the environment (Jahan and Igbal, 1992). All combustion<br>releases gases and particles into the air. These can include sulphur and nitrogen<br>oxides, carbon monoxide and soot particles as well as smaller quantities or<br>toxic metals, organic molecules and radioactive isotope (Agbaire and<br>Esiefarienche, 2009). Over the years, there has been a continuous increase in<br>human population, road transportation, vehicle traffic and industries which has<br>resulted in further increase in concentration of gaseous and particulate<br>pollutants (Joshi, et al ., 2009).<br>Adverse effects of air pollution on biota and ecosystems have been<br>demonstrated worldwide. Environmental stress, such as air pollution is among<br>the factors that limits plants productivity and survivorship (Woo, et al., 2007)<br>Dust from quarry sites is a major source of air pollution, though the<br>severity will depend on factors like the local microclimate conditions, the<br>concentration of dust particles in the ambient air, the size of the dust particles<br>and their chemistry. For example, lime stone quarries produce highly alkaline<br>and reactive dusts, whereas coal mines produce acidic dust. The air pollution is<br>a nuisance in terms of deposition on surfaces and its possible effects on health,<br>especially for those with respiratory problems. It produces dust that can also<br>have physical effects on the surrounding plants, such as blocking their<br>photosynthetic activities that occupy an important position in the existence of<br>life because of their ability to maintain a balance in the volume of oxygen and<br>carbon dioxide which leads to the purification of the environment.<br>1.4.1 AIR POLLUTION AND MEDICINAL PLANTS<br>Higher temperature causes heat stress in plants. This means they grow<br>less and produce fewer crops. In some cases, the plants do not reproduce at all<br>since excessive heat causes sterility of the pollen grains. A temperature increase<br>may be beneficial in areas which are very cold at present. Changes to our<br>climate are happening more quickly now than they have ever done before in the<br>world due to different industries and developments. Though as natures may<br>have it some plants due adapt to the conditions often. Some studies have<br>demonstrated that temperature stress can affect the secondary metabolites and<br>other compounds that plants produce. Water availability directly affects the<br>growth of plants and how much crop they produce. In most part of Africa there<br>is not enough water even in normal conditions for high crop yields for instance,<br>in contrast in Nigeria most plant are grown with enough water and difference in<br>crop growth between the continents can be clearly seen. So changes in<br>temperature and precipitation patterns as a result of climate change are likely to<br>be bad for large areas of the world but may increase crop production in other<br>regions. However, one of the likely outcomes of climate change is also an<br>increase in severity of rain storms and drought. These are likely to have large<br>devastating effects on agriculture and medicinal plant plantation.<br>The increase in atmospheric carbon dioxide (C02) levels resulting from<br>Fossil fuel combustion has fertilizing effect on most plants since C02 is needed<br>for photosynthesis. Conversion of carbon dioxide and water into the simple<br>sugar (glucose) emits oxygen making it possible for animals to lives on Earth.<br>Sunlight is the energy that powers this reaction. Scientific experiment has<br>shown that increasing atmospheric CO2 levels leads to an increase in plant<br>growth (shad, et al., 2008).<br>1.4.2 TYPE OF AIR POLLUTANT AND THEIR SOURCES<br>There are many atmospheric pollutants that have been in existence but few<br>of them are to be discussed here. The sources of air pollutants include human<br>activities, domestic sectors, industry, agriculture, transport and nature as well.<br>Here, the pollutants, their sources and toxic effects to the environment are<br>being discussed.<br>1. Solid particles; These are mostly produced by combustion, plants<br>industrial processes like mineral extraction, cement work, steel works,<br>foundries, glass works, gypsum quarries and fine chemistry. They have<br>carcinogenic and mutanogenic effect.<br>2. Sulphur dioxide (So2):This is released by coal mining, lignites,<br>petroleum coke, and heavy fuel oil, domestic heating oil, diesel oil,<br>production of paper pulp, oil refining, nature and fire wood.<br>3. Nitrogen oxide (No2): This is produced by combustion of fossil fuel and<br>from new industrial processes like fertilizer production, surface<br>treatment and phytochemical oxidants. In the presence of oxygen, it is<br>converted to No2 in the furnace. The reaction continues slowly in the<br>atmosphere and gives a brownish color of the layer of polluted air 100<br>meters above town and causes green house effect.<br>4. Carbon monoxide: It is gotten from incomplete combustion,<br>agglomeration of mineral steel work, incineration of waste and car<br>exhaust fumes.<br>5. Volatile organic compounds: These are released from methane, solvents,<br>paint application, printing glues and adhesives, rubbers, biomass,<br>perfumes, cosmetic, News papers and tobacco.<br>6. Heavy metals: There are various sources of heavy metals which<br>contaminate the atmosphere. Examples of some of them are:<br>(a). Arsenic (As) comes either from trace of this metal in solid mineral fuels<br>and in heavy fuel oil , or else from certain raw materials used in<br>processes such as glass making, non-ferrous and ferrous metals working.<br>(b) Cadmium (Cd) is formed mainly through the manufacture of zinc and<br>the incineration of waste .Burning solid mineral fuel, heavy fuel oil and<br>biomass account for a significant proportion of emission.<br>(c) Chromium (Cr) comes essentially from the production of glasses,<br>cement, ferrous metallurgy and foundries.<br>(e) Copper (Cu) comes from the erosion of over headed cables by railway<br>traffic. In addition, as for the other heavy metals, ferrous and non-ferrous<br>metals from metal production processes, the treatment of waste, and<br>combustion are all, to varying degree major sources of copper emission.<br>(f) Mercury (Hg) is emitted in small but still excessive quantities by the<br>combustion of coal and oil, the production of chlorine, and also by the<br>incineration of household, hospital and industrial waste. Preventive<br>action has considerably reduced mercury emission in recent years. Other<br>type of pollutants are Nickel, Lead, Selenium, Zinc, carbon dioxide,<br>methane, Nitrous oxide, Chlorofluorocarbon, Hydroflurocarbons,<br>Perflurocarbons, Sulphur hexafluroxide , Hydrofluoric acid , Ozone, and<br>Hydrogen sulphide (Citepa, 2012).<br>1.4.3 THE THRESHOLD AT WHICH AIR POLLUTANT EFFECT<br>MEDICINAL PLANTS AND THEIR SYMPTOMS.<br>This is injury or symptoms shown by impact of metallic object on some<br>plant by pollutants. These symptoms are always triggered at some threshold<br>extent. The presence of pollutants like, Sulphur dioxide causes intervenial<br>necrotic blotches, red brown die back or banding in pines, in plants. Nitrogen<br>dioxide causes interveinial necrotic blotches similar to those symptoms<br>produced by Sulphurdioxide. Fluoride produces red brown distal necrosis in<br>pines. Ammonia leads to tip margin necrosis at the threshold dose of 55pm<br>(38×10μg/m3) for 1 hour. Chlorine causes interveinial necrotic blotches<br>similar to So2 at the threshold of 0.5-1.5ppm (1400-4530μg/m3) for 0.5-3hr.<br>Ethylene leads to chlorosis, necrosis, abscission, dwarfin, premature<br>defoliation of medicinal plants but the threshold variably undetermined. Ozone<br>causes upper surface broncing chlorosis and early senescence at the threshold<br>of (157μg/m-3) for 12-13 hrs. Acidic rain shows necrotic sports, distal necrosis<br>pines on medicinal plants at the pH &lt; 3.0 (Citepa, 2012).<br>1.4.4 EFFECT OF AIR POLLUTION ON LEAF MORPHOLOGY<br>Pollutants can cause leaf injury, stomata damage, premature senescence,<br>decrease photosynthetic activity, disturb membrane permeability and reduce<br>growth and yield in sensitive plant species (Tiwari, et al., 2006). Reductions in<br>leaf number may be due to decreased leaf production rate and enhanced<br>senescence. The reduced leaf area result in the reduced absorbed radiations and<br>subsequently in reduced photosynthetic rate.<br>Air pollution stress leads to stomatal closure, which reduces co2<br>availability in leaves and inhibits carbon fixation. Plants that are constantly<br>exposed to environmental distress absorb, accumulate and integrate these<br>pollutants into their systems. Reports have shown that depending on their<br>sensitivity level, plants shows visible changes which would include alteration in<br>the biochemical processes or accumulation of certain metabolites (Agbarie and<br>Esiefarienrhe, 2009).<br>Sulphur dioxide, nitrogen oxides, acid co2 as well as suspended<br>particulate matter, when absorbed by the leaves may cause a reduction in the<br>Concentration of photosynthesis pigment like chlorophyll and carotenoids<br>which directly affected metabolites. One of the major impacts of air pollution is<br>the gradual disappearance of chlorophyll that leads to yellowing of leaves,<br>which may be caused by decrease in the capacity for photosynthesis.<br>Chlorophyll is the most photoreceptor in photosynthesis, the light driven<br>process in which carbon dioxide is fixed to yield carbohydrates and oxygen.<br>When plants are exposed to environmental pollution above the normal<br>physiological acceptable range, photosynthesis gets inactivated. What happen to<br>leaf morphology, pigment content also affects the efficacy of the crude extracts<br>(Joshi and Swami, 2007).<br>1.4.5 EFFECT OF AIR POLLUTION ON PLANT SUGAR CONTENTS<br>Mainly soluble sugar from plants and vegetation are source of energy for<br>living organisms. Studies have revealed that there is always loss of soluble<br>sugar in all tested species at all polluted sites. Loss of soluble sugar content in<br>polluted area can be related to increased respiration and decreased CO2 fixation<br>because of chlorophyll deterioration (Tripathi and Guatam, 2007). Reseachers<br>have found out that pollutants like SO2, NO2, and H2S under hardening<br>condition can lead to loss of soluble sugar in the leaves of plant grown in<br>polluted Area. They have also shown that even in sensitive trees loss of sugar<br>has occurred and is probably due to photosynthetic inhibition or stimulation of<br>respiration rate.<br>Increase in amount of soluble sugar is a protecting mechanism of leaves.<br>Soluble sugar in pine needle decreased on ozone exposure and the more a plant<br>is resistant to air pollution the more the increase in soluble sugar level eg<br>Dodonea viscoss and prosopis juliflora (Abedi, et al., 2009).<br>1.4.6 EFFECT OF AIR POLLUTION ON PLANT PROLINE<br>Proline is an osmotic accumulation in response to several stresses that<br>may have a role in defending plants life, pigment destruction, depletion of<br>cellular lipids and peroxidization of polyunsaturated fatty acid.<br>Many researchers have shown that environmental stress, causes increase<br>in tree proline Contents. Environmental stresses like high temperature, low<br>temperature, drought, air pollution and soil pollution can lead to reaction of<br>oxygen species in plant cells which is always cytotoxic to all organisms when a<br>plant is exposed to high environmental stress, this forces the chloroplast into an<br>excessive excitation energy level which in turn causes increase in generation of<br>reactive oxygen species and lead to oxidative stress. The proline is known as<br>free radical scavenger to protect plants. Some other amino acids such as<br>tryptophan, tyrosine etc, do the same but proline is counted more important<br>because of its high Concentration on a plant during environmental stress<br>(Tiwari, et al., 2006).<br>1.4.7 GENERAL EFFECT OF AIR POLLUTION ON MEDICINAL<br>PLANTS<br>Much experimental work has been conducted on the analysis of air<br>pollutant effects on crops and vegetations as various levels ranging from<br>biochemical to ecosystem levels. Environmental stress, such as air pollution is<br>among the factor that limits plants productivity and survivorship (Woo, et al.,<br>2007). When exposed to air bone pollutants, most plants experienced<br>physiological changes before exhibiting visible damage to leaves (Liu and<br>Ding, 2008). The atmospheric S02 adversely affects various morphological and<br>physiological characters of plants. High soil moisture and high relative<br>humidity aggregate S02 injury in plants.<br>Industrialization and the automobile are responsible for maximum amount<br>of air pollutants and the crop plants are very sensitive to gaseous and<br>particulate pollutions (Joshi, et al., 2009). Vegetation is an effective indicator<br>of the overall impact of air pollution and the effect observed is a time averaged<br>result that is more reliable than the one obtained from direct determination of<br>the pollution in air over short period. Although, a large number of trees and<br>shrubs have been indentified and used as dust filters to check the rising urban<br>dust pollution level (Rao, 1979).<br>Plants provide an enormous leaf tree impingement, absorption and<br>accumulation of air pollutants to reduce the pollutant level in the environment<br>with a various extents for different species. The use of plants as monitors</p><p>&nbsp;</p> <br><p></p>