Ameliorative effect of indole acetic acid and naphthalene acetic acid on some biochemical parameters of soybean exposed to lead toxicity

Abstract

Lead (Pb) is a potential pollutant that readily accumulates in soils and sediments widely occurred as a result of human, agricultural and industrial activities. IAA and NAA belongs to plant hormone auxin that promote plants growth. The effects of lead (Pb) phytotoxicity include stunted growth, chlorosis, blackening of the root systems, alteration in water and nutritional status of plants, inhibition of enzyme activities and so on. This study therefore  aim at examining possible ameliorative effects of Indole acetic acid( IAA) and Naphthalene acetic acid (NAA) on some biochemical parameters (photosynthetic pigments, mineral elements and antioxidant enzymes) of soybean  exposed to lead( Pb) toxicity.

      One thousand (1000)mg/L of PbNO₃ was applied to 5kg of soil in a polythene bag It was allow to acclimatize for 2 weeks after which the seed were sown in the soil. Fourty (40)mg/L, 80 mg/L and 120mg/L each of IAA and NAA were prepared and applied by foliar method after 5 weeks  of planting. The plants  were  harvested after 7 weeks and was partitioned into root, stem and leaf for analysis. The results showed that the level of chlorophyll a, b and carotenoid, mineral elements and antioxidant enzymes significantly increased (P˂0.05) in the root, stem and leaf of soybean treated with different concentration of Indole acetic acid (IAA) and Naphthalene acetic acid (NAA) as compared with the control (C^+ve). All bioregulators (IAA and NAA) concentrations significantly decreased (P˂0.05)  in the level of Pb²⁺ (except 40mg/L IAA in the root and leaf while all concentration have significant effects in the stem) and also all concentration of (IAA and NAA) significantly increased (P˂0.05) in the level of biochemical parameters to different extent as compared to control(C^+ve). These results  shows that Indole acetic acid (IAA)  and Naphthalene acetic acid ( NAA) could ameliorate the Pb toxicity  and therefore will be of relevance to agricultural producers .