Effect of high light intensity on photoinhibition, oxyradicals and artemisinin content in Artemisia annua L.

Abstract

Artemisia annua L. produces a compound called artemisinin that is a potent anti-malarial compound. However concentration of artemisinin within the plant is typically low (less than 0.8% of dry mass) and currently supply of the drug by the plant does not meet world demand. This investigation was carried out to determine whether high intensity light treatment would increase production of artemisinin in leaves of A. annua. Photoinhibition (14%) was induced in leaves of A. annua when they were subjected to 6 h of high-intensity light [2,000 µmol(photon) m-2 s-1 ]. Maximum photochemical efficiency of PSII showed a recovery of up to 95% within 24 h of light induced inhibition. During the light treatment, photochemical efficiency of PSII in leaves of the high-intensity light-treated plants was 38% lower than for those from leaves of plants subjected to a low-intensity-light treatment of 100 µmol(photon) m-2 s-1. Non-photochemical quenching of excess excitation energy was 2.7 times higher for leaves treated with high-intensity light than for those irradiated with low-intensity-light. Elevation in oxidative stress in irradiated leaves increased presence of reactive oxygen species (ROS) including singlet oxygen, superoxide anions, and hydrogen peroxide. Importantly, the concentration of artemisinin in leaves was twofold higher for leaves treated with high-intensity light, as compared to those treated with low-intensity light. These results indicate that A. annua responds to high irradiance through nonphotochemical dissipation of light energy yet is subject to photoinhibitory loss of photosynthetic capacity. It can be concluded that A. annua is capable of rapid recovery from photoinhibition caused by high light intensity. High light intensity also induces oxidative stress characterized by increased concentration of ROS which enhances the content of artemisinin. Such a light treatment may be useful for the purpose of increasing artemisinin content in A. annua prior to harvest.

Irradiation and nitrogen regulate growth and physiology in Horsfieldia hainanensis seedlings

“…Irradiance requirements differ among plant species, and unsuitable irradiance can inhibit plant growth. Too high irradiance results in photoinhibition (Poulson and Thai 2015), consistent with our results showing the inhibition of H. hainanensis seedling growth under full natural irradiance. Under the stress caused by full natural irradiance, N supply was beneficial for growth, leading to increases in both leaf area and total dry mass.…”

Dynamics of Mineral Uptake and Plant Function during Development of Drug-Type Medical Cannabis Plants

“…This is supported by our finding that concentrations of photosynthetic pigments were generally highest under the vegetative growth conditions (Figure 5), potentially to increase light capture per unit leaf area since light intensity was lower at that phase. It is important to note that the relative decrease in plant function under reproductive growth conditions might have resulted from the high light intensity, which could have caused photo-inhibition damages and induced oxidative stress that damaged cell homeostasis [70,71]. Indeed, our results show that membrane stability was lower and electrolyte leakage from the cell membrane was higher under the reproductive growth conditions (Figure 4H), as was already shown to occur in other plant species [72,73].…”

Assessing shade stress in leaves of turf-type tall fescue (Festuca arundinacea Schreb.)

“…This suggests that the ultrastructure change is regulated by phytohormones as a response to light fluctuations. This was supported by the findings in light response of Artemisia annua L. (Poulson and Thai 2015) and Solanum lycopersicum L. (Poór et al 2019). Anderson et al (2012) reviewed large amounts of publications regarding the thylakoid architecture changes as a mechanism of adaptation to shade in plants.…”