Air pollution is a world-wide problem and became a concern of many governments. Broadly, it is defined as the presence of one or more contaminants like dust, smoke, and many kinds of air pollutants which could damage various life forms (Patidar, 2016). One of the causes of this problem is rapid industrialization that led to an increase in vehicular traffic (Depalakshmi, 2013). Air pollution due to vehicular traffic and industrial waste can cause detrimental impact to plants living in the environment. Scientists has documented that pollutants from automobiles have major effects on the growth and development of plants. Some of these effects are fruiting, flower development, leaf senescence and leaf surface wax characteristics, biomass production, seed germination, seedling growth, physiological and biochemical characteristics and plant growth (Iqbal, 2015). In addition, one of the most common impacts of air pollution is the gradual disappearance of chlorophyll and the yellowing of leaves (Sharma, 2017).
Chlorophyll is a pigment important in the process of photosynthesis. Thus, chlorophyll content is an important factor to evaluate the effect of air pollutants on plants as it plays an important role in plant metabolism. (Petrova, 2017). Chlorophyll content can signify the quality of its productivity through photosynthesis as well as its growth and development. Impact of air pollution to the chlorophyll content of plants had been documented in previous literature. In previous studies, it was found out that plants like A. indica, C. erectus, G.officinale and Eucalyptus sp. (Iqbal, 2015) Azadirachta indica, Nerium oleander, Mangifera indica and Dalbergia sissoo (Giri, 2013) has reduced amount of chlorophyll if they are exposed to air pollution. In this study, response of (2) two local trees to air pollution was investigated. Specifically, the amount of chlorophyll content of species in polluted and non-polluted areas was quantified using UV-Vis spectrophotometer.
Two (2) study sites were considered in the conduct of the study. The designated non-polluted area (being less exposed to vehicular traffic) is located at Lily Hill, Clark Freeport Zone, Pampanga. The area is considered less polluted because of its thick vegetation compared to the other site. In addition, the area is less exposed to vehicular activities than the other site. The designated polluted area in the study is along Mc Arthur High Way in Balibago, Angeles City and Dau, Mabalacat City, Pampanga. The area is polluted because it is main high way and is frequently exposed to vehicular traffic. The study was conducted in July 2018. Laboratory analysis of collected samples were doneat the Science Laboratory of Philippine Science High School-Central Luzon Campus, Clark Freeport Zone, Pampanga.
Two (2) species of trees found in the locality were used in the investigation. These are Pterocarpus indicus (Narra) and Leucaena leucocophala (Ipil-Ipil). Samples of leaves were collected from two (2) trees per species in the two study sites. Laboratory analysis of the chlorophyll contents of the plant species were done on the day of collection. Chlorophyll content of the leaves were determined using the procedure given below.
Fresh sample leaves were washed with distilled water until all the dirt were removed. Samples were then cut in small pieces separately per species and per tree. 50 grams of sample per species was weighed using a digital balance. Chlorophyll of the samples were extracted by grinding the leaves in a mortar and pestle with 20 mL of 80% laboratory grade acetone. The resulting acetone solution which contains the chlorophyll were read at wavelengths measuring 664 and 647 nm using Ultraviolet-visible Spectrophotometer (UV-Vis) to approximately quantify the chlorophyll a, chlorophyll b and total chlorophyll content of the plant sample. The chlorophyll a, chlorophyll b and total chlorophyll were calculated using the formula below (Musyimi, 2015)
Chlorophyll a= 13.19 A664-2.57 A647 (mg g-1 fresh weight).
Chlorophyll b= 22.1 A647- 5.26 A664 (mg g-1 fresh weight).
Total chlorophyll = 7.93 A664+ 19.53 A647 (mg g-1 fresh weight).
where, A664 is the absorbance at 664nm A647 is the absorbance at 647 nm.
The results show that there is a difference in the amount of chlorophyll in the leaves of L.leucocophala found in polluted and non-polluted areas. As shown in Table 1, the total chlorophyll content of L.leucocophala found in non-polluted area is higher than those which are found in polluted area. This also holds true for the chlorophyll a and b of this plant species. Using t-test of independent samples, results show that the difference between the total chlorophyll content of L.leucocophala in polluted and non-polluted areas is significant at 0.05 level of confidence (p value of 0.28). This result indicates that vehicular pollution may be a factor that could influence the amount of chlorophyll in plants living in a polluted area.
The result of this investigation is supported by the previous studies studies conducted related to it. In the study of XXXX on (A. indica, C. erectus, G.officinale and Eucalyptus sp.), they found out that vehicular activities induced air pollution problem and affected on the level of chlorophyll pigments in trees which were exposed to road side pollution. In addition, A study conducted by Giri et al.  indicated a decline in the chlorophyll content in trees growing in the industrial areas and it was suggested that the reduction in chlorophyll content was due to degradation of chlorophyll into phaeophytin by the loss of magnesium ions.
The present study showed that the air pollution has influence on the chlorophyll content of L.leucocophala. Plants which are exposed to air pollution may have a reduced amount of chlorophyll which can affect their growth. Other plants like the P. indicus may not be easily be easily affected by vehicular pollution. It is recommended however that, the study may be further by including more sample trees and from different areas. It is also recommended that level of pollutants in the study site will be explored to establish a clear correlation between the responses of plants to air pollution.
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