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