Physio-biochemical, anatomical and functional responses of Helianthus annuus L. and Brassica juncea (Linn) to cypermethrin pesticide exposure

Abstract

Pesticides are applied all over the world to protect plants from pests. However, their application also causes toxicity to plants, which negatively affects the growth and development of plants.This study compared the physiological, biochemical and anatomical modifications of two oil seed crops viz., Helianthus annuus L. and Brassica juncea under different levels of pesticides. The present research was aimed to assess responses at the biochemical, physiological and anatomical levels to Cypermethrin (CYP) pesticide to discriminate the effects of osmotic stress and micronutrients availability. The two different concentrations of CYP-pesticide (20 mg /kg and 40 mg /kg) were examined. The obtained results showed that as the concentration of cypermethrin increased in soil, the fresh and dry weight of growing plants gradually decreased. The application of 40 mg /kg −1 soil of cypermethrin reduced the fresh weight of root in both H. annuus and B. juncea (up to 33 % and 29.4 % %, respectively) decreased root length (up to 2.3 % and 11 %, respectively). While shoot length was increased in both plant species at both levels of CYP relative to control. Shoot fresh weight decreased at 20 mg /kg CYP-treatment in H. annuus whereas in B. juncea at same level of cypermethrin increased fresh weight of shoot was found relative to un-treated seedlings. Reactive oxygen species viz., H2O2 and MDA contents in roots increased by 40 mg/kg-1 CYP in B. juncea followed by H. annuus (upto 50.27 % and 19.79 %; 36.33 % and 35.21 %, respectively). Furthermore, pesticide increased the activities of antioxidant enzymes in H. annuus followed by B. juncea. SOD, POD and CAT enzyme activities significantly decreased in B. juncea under 40 mg/kg-1 CYP by 38.8 %, 44.78 % and 36.83 %, respectively. In 20 mg /kg cypermethrin treatment declined antioxidant enzyme activities were found in H. annuus shoot compared to B. juncea shoot. In case of B. juncea increased APX enzyme activity was observed at 20 mg /kg-1 cypermethrin treatment. While significantly decreased activities of an antioxidant enzymes were found to be at 40 mg /kg CYP-treatment. The main aimed of this study to determine the anatomical responses of H. annuus and B. juncea roots to the cypermethrin exposure. Cypermethrin stress (40 mg /kg-1) change the root diameter (smaller), damaged epidermis layer, irregular form of epidermal cells of both species. The area of vascular bundle is decreasing when increasing the cypermethrin pesticide. Moreover, in stem, epidermis thickness was observed only in B. juncea xylem thickness increased in H. annuus at 20 mg /kg treatment, while in B. juncea non-significant difference was observed at this trait relative to un-treated plants. Phloem thickness raises and pith area in both species at lower concentration of cypermethrin. Leaf collenchymatous cell area was increased at both plant species at 20 mg /kg. Epidermis, spongy mesophyll and palisade mesophyll thickness increased when increased cypermethrin. Mineral uptake by H. annuus and B. juncea from cypermethrin treated soil was measured and also Pearson correlation was measured between all analyzed traits of plants. PCA clearly differentiated all treatments and growth parameters of both plant species. Thus, findings of present study confirmed that overdose of pesticides exhibited toxic effects on different growth, physiological and biochemical attributes of tested plants and pesticide also alter structural changes in plant tissues.