One of the major abiotic stresses that cause environmental pollution is heavy metal stress. In the present investigation, copper (Cu) toxicity caused morphological and cellular damages to the Artemisia annua L. plants but supplementation of abscisic acid (ABA) ameliorated the damaging effect of Cu. Copper toxicity significantly reduced the shoot and root lengths; fresh and dry weights of shoot. However, exogenous application of ABA to Cu-treated plants significantly attenuated the damaging effects on plants caused by Cu toxicity. Copper stress also reduced the physiological and biochemical parameters, but ABA application ameliorated the negative effects of Cu in the affected plant. Accumulation of Cu in plant tissues significantly increased the membrane damage and oxidative enzyme activities such as catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD). Further, the impact of high concentration of Cu on density, area and ultrastructure of glandular trichomes and artemisinin content was studied. Moreover, the foliar application of ABA improved the area, density of glandular trichomes and secured the plant cells from Cu toxicity. Therefore, this investigation indicated that the exogenous application of ABA protects A. annua plant by increasing antioxidant enzymes activity, which helps in maintaining cell integrity of leaves and results in increased artemisinin production.
Keywords: Abiotic stress; Abscisic acid; Artemisinin; Copper toxicity; Oxidative damage; Photosynthetic efficiency.
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