Enzymatic defense of Cyperus brevifolius in hydrocarbons stress environment and changes in soil properties

Abstract

Hydrocarbons or crude oil contamination of soil is still a burning problem around the globe. The herbs competent that are to survive in hydrocarbons contaminated habitats have some adaptive advantages to cope up with the adverse situations prevailing in that environment. In the present study, the adaptive response of Cyperus brevifolius in the heavily polluted soil with crude oil has been investigated in terms of survivability, changes in productivity, antioxidants, phytochemicals and functional group pro files of the plant species. Besides, changes in enzymes, beneficial bacterial population and physico-chemical conditions of contaminated soil were also studied during 60 days of experimental trials. The results showed significant enhancement in activities of soil dehydrogenase, urease, alkaline phosphatase, catalase, and amylase whereas reduction in cellulase, polyphenol oxidase and peroxidase activities. There was a significant increase in nitrogen fixing, phosphate and potassium solubilizing bacterial population, improvement in physico-chemical conditions and a decrease in total oil and grease (TOG) levels. Besides there was significant variations in the productivity parameters and antioxidant profiles of Cyperus brevifolius in hydrocarbons stress condition suggesting enzymatic defense of the herb. The fourier-transform infrared (FT-IR) analysis indicated uptake and metabolism of some hydrocarbon components by the experimental plant from the hydrocarbons polluted soil.

Figure 1

(a) Showing the changes in dehydrogenase and urease activities in crude oil contaminated soil at the beginning and by the end of the experimental trials. Values are mean, n = 3, error bars indicate SD. Different letters above error bars stand for significant differences of the values for a particular enzyme among the different treatments (ANOVA, LSD test, P ≤ 0.05). Black axis-for treatments details, Light blue axis-for dehydrogenase activity, Purple axis-for urease activity. T1- Crude oil contaminated soil (Initial), T2- Crude oil contaminated soil without Cyperus brevifolius, T3- Crude oil contaminated soil + Cyperus brevifolius. (b) Showing the changes in alkaline phosphatase and catalase activities in crude oil contaminated soil at the beginning and by the end of the experimental trials. Values are mean, n = 3, error bars indicate SD. Different letters above error bars stand for significant differences of the values for a particular enzyme among the different treatments (ANOVA, LSD test, P ≤ 0.05). Black axis-for treatments details, Blue axis-for phosphatase activity, Brown axis-for catalase activity. T1- Crude oil contaminated soil (Initial), T2- Crude oil contaminated soil without Cyperus brevifolius, T3- Crude oil contaminated soil + Cyperus brevifolius. (c) Showing the changes in amylase, cellulase, polyphenol oxidase and peroxidase activities in crude oil contaminated soil at the beginning and by the end of the experimental trials. Values are mean, n = 3, error bars indicate SD. Different letters above error bars stand for significant differences of the values for a particular enzyme among the different treatments (ANOVA, LSD test, P ≤ 0.05). Black axis-for treatments details, Light blue axis-for amylase and cellulase activities, Violet axis-for polyphenol oxidase and peroxidase activities. T1- Crude oil contaminated soil (Initial), T2- Crude oil contaminated soil without Cyperus brevifolius, T3- Crude oil contaminated soil + Cyperus brevifolius.

Figure 2

Showing the changes in DPPH, H₂O₂ free radical scavenging activities and reducing power assay of C. brevifolius extracts grown in crude oil contaminated soil and control soil. Values are mean, n = 3, error bars stand for SD. Significant differences of the values for a particular parameter at a particular concentration for different treatments and standard are indicated by different letters (ANOVA, LSD test, P ≤ 0.05). Black axis-for concentration wise treatments and standards, Brown axis-for DPPH and H₂O₂ free radical scavenging activity, Green axis-for reducing power assay.T4- Non-contaminated soil + Cyperus brevifolius, T3- Crude oil contaminated soil + Cyperus brevifolius, BHT- Butylated hydroxytoluene.