Comparative Physiological and Biochemical Responses of Spinach and Tomato to Roadside Environmental Stress in Sulaimani

• Sajida Saeed Aziz

  Author

This study examined the effects of roadside heavy-metal contamination on the physiological and biochemical responses of spinach (Spinacia oleracea L.) and tomato (Solanum lycopersicum L.) in Sulaimani, Kurdistan Region, Iraq. the former a roadside habitat that has been highly exposed to vehicular fumes and the latter a farmland that is quite remote to the vehicular emissions and therefore has minimal contamination.

Inductively Coupled PlasmaOptical Emission Spectrometry (ICPOES) was used to determine the lead (Pb) and cadmium (Cd) in soil and leaf samples. Measures of physiological parameters such as chlorophyll content in terms of SPAD, chlorophyll fluorescence (Fv/Fm), antioxidant enzyme superoxide dismutase (SOD) activity, measurement of lipid peroxidation through malondialdehyde (MDA) levels and soluble sugar content were measured to determine the response of plants to stress.

The findings found that there were considerably greater levels of Pb and Cd in the soils and plant tissues at the roadside location as compared to the remote agricultural location. Increased levels of metal were correlated with significant decreases in SPAD and Fv/Fm values which are indicative of a photosynthetic inhibition. At the same time the SOD activity and MDA levels were elevated which indicates the activation of antioxidants defenses and oxidative stress. Under roadside conditions, soluble sugar concentrations were reduced significantly, which supported the fact of metabolic disruption.

The accumulation of Pb and Cd and oxidative response towards heavy metal were higher in spinach than in tomato, indicating spinach was more sensitive to heavy metal stress and a better bioindicator species. The results highlight the relevance of environmental monitoring program that includes physiological parameters and suggest avoiding the cultivation of leafy vegetables near high-traffic roads.

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