Silicon-mediated cellular resilience mechanisms against copper toxicity and glandular trichomes protection for augmented artemisinin biosynthesis in Artemisia annua
2020
Zehra, Andleeb | Choudhary, Sadaf | Wani, Kaiser Iqbal | Naeem, M. | Khan, M. Masroor A. | Aftab, Tariq
The micronutrients could cause severe toxicity to plants at higher concentrations. In this investigation, copper (Cu) toxicity caused morphological and cellular damages to the Artemisia annua L. plants but application of silicon (Si) ameliorated the damaging effects of Cu. Copper toxicity reduced the lengths of shoot and root and also fresh and dry weights of shoot of the plants. However, exogenous application of Si to Cu-treated plants significantly alleviated the harmful effect on plants by metal stress. Copper stress also lowered the photosynthetic potential and content of total chlorophyll as well as hindered the chlorophyll fluorescence; however, Si supplementation recovered the negative impacts of Cu in the plants. The treatment of Cu resulted in accumulation of this metal in roots and shoots of A. annua plants. Deposition of Cu resulted in oxidative stress in plants as evident by increase in 2-thiobarbituric acid reactive substances (TBARS) content and catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) enzyme activities. However, addition of Si prevented adverse effects of Cu toxicity and prevented excess of Cu in root and shoot tissues and TBARS content in the cells of disturbed plants. The significant deleterious impact of high concentrations of Cu on density and ultrastructure of glandular trichomes and artemisinin content was also noticed. Furthermore, the Si supplementation improved the density of glandular trichomes and protected the plant tissues from Cu toxicity, thereby upregulating artemisinin biosynthesis. Therefore, the results indicated that the exogenous application of Si protect A. annua plants from Cu toxicity by preventing deposition of Cu in root and shoot tissues, by increasing the antioxidant capacity, which maintained the structure and integrity of leaves and also helps in increased artemisinin production.
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