Influence of arsenic stress on growth, physiological activities and artemisinin production in two varieties of Artemisia (Artemisia annua) differing in artemisinin yield

Abstract

Artemisinin, extracted from the leaves of Artemisia annua L., has been recognized as an effective and safe remedy against malaria. A pot experiment was conducted according to randomized block design using five replicates to screen the A. annua L. varieties, namely 'CIM-Arogya' and 'Jeevan Raksha' under arsenic stress. Four concentrations of arsenic [0 (control), 15, 30 and 45 mg kg-1 soil] were applied to the soil. Measurements for growth characteristics, physiological attributes, biochemical parameters, yield and quality attributes were carried out at pre-flowering [90 days after planting (DAP)] and flowering (120 DAP) stages. The variety 'Jeevan Raksha' was more adversely affected by arsenic stress than the 'CIM-Arogya', suggesting that the 'CIM-Arogya' was more arsenic tolerant than the 'Jeevan Raksha'. The highest arsenic concentration (45 mg kg-1 soil) proved most toxic dose as compared to other arsenic doses applied. It reduced the rate of photosynthesis and leaf-chlorophyll content significantly both at 90 and 120 DAP. The activities of CAT, POX and APX were also rapidly stimulated due to the highest concentration of arsenic at both the growth stages. Noticeably, all applied doses of arsenic significantly increased the production of artemisinin in the leaves. As compared to control, 'CIM-Arogya' contained the maximum artemisinin content under the highest arsenic stress, increasing the artemisinin content by 38.0 and 42.6% at 90 and 120 DAP, respectively; while, 'Jeevan Raksha' showed an increase in artemisinin content by 32.6 and 35.7% at the respective dates of sampling. At the highest arsenic stress, the yield of artemisinin was increased by 42.9 and 45.7% in 'CIM-Arogya' and by 37.5 and 40.5% in 'Jeevan Raksha'. Generation rate of H2O2 increased consistently when arsenic was applied irrespective of the varieties used, indicating the role of H2O2 in artemisinin biosynthesis in A. annua L.