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In order to investigate the heavy metals accumulation and their effects on roadside trees Conocarpus erectus. The total content of Pb and Mn was determined using atomic absorption spectrophotometry was conducted. Average concentration 10.578 ± 3.48 μg/gm of Pb and 91.98 ± 30.03 μg/gm of Mn was found. Moreover, there were variations in the level of both these heavy metals in different samples of Conocarpus tree that were collected from different locations along the road side due to different level of exposure to Pb and Mn. This physiological response of Conocarpus plant towards Pb and Mn suggests that roadside plants are good indicators of heavy metals accumulation and their subsequent effects on the environment. The tremendous increase in auto vehicles in recent years has caused the environment to become a continuous source of pollutants, including heavy metals. Plants show considerable amount of lead and other metals in their tissues near busy roads (Dalal and Bairgi 1985, Rashid and Mukherjee 1990, Iqbal et al. 1999). Tetra-ethyl lead, which is an anti-knocking additive, is added to gasoline, that escapes from auto exhaust and mix into the air, soil and water (Iqbal and Shazia 2004). Lead has long been known as a potential health hazard (Shannon and Graef 1996). A number of studies have determined lead concentrations in dust, soil, particulates, and leaf samples in different urban areas around the world. Dust is a significant source of lead and can raise the blood lead levels in humans, particularly in children (Aydinalp and Marinova 2004). Manganese is used as a component of tyre and motor oil (Shaikh et al. 2006). Particulate type air pollutants such as ash, dirt and grit land on the top of leaves do not enter the leaf but may damage it by mechanical abrasion of surface. Particulate matter can also block the sun light and there by reduce the food processing ability of the plants. Deposition of lead on leaves mainly depends upon the characteristics of the leaf surface and the wind speed, and to lesser extent on the other environmental conditions like temperature, humidity etc. (Agarwal 1991). The plants, growing near highways are usually exposed to more automobile lead and manganese discharge than any other location. Small amount of lead, manganese and other heavy metals can penetrate the cuticle probably through stomata and other openings. In an earlier study, it has been found that stomata of plants growing on roadside and central district of Karachi are blocked to the extent of 20 50% depending on the location (Ahmed et al. 2005). The present study was conducted in order to investigate heavy-metals (Pb and Mn) accumulation and their effects on roadside trees Conocarpus (Conocarpus erectus) in the Mauripor to Hawks bay Road. Leaf samples of Conocarpus erictus tree were collected from eight kilometers area (from Mauripur to fish point (Beach Bar-BQ Restaurant), along Hawks bay road Karachi, Pakistan. There were four rows of plants; each row was composed of 1500 plants, so there were approximately *Author for correspondence: . Department of Botany, Hazara University Mansehra 21300, KP, Pakistan.

Lead and manganese accumulation on leaves of road side plants from Mauripor to Hawks Bay road, Karachi, Pakistan