Studies on dynamics of growth and biosynthesis of artemisinin in hairy roots of Artemisia annua L.
Seven hairy root lines with the properties of fast growth and high artemisinin contents were selected from 747 hairy roots induced by transformation of Artemisia annua L. strain 025 with Agrobacterium rhizogenes ATCC15834. The differences of growth rates and artemisinin contents among the 7 selected hairy root lines were extremely significant, of which HR-9 gave the highest yield of artemisinin, reaching 33.25 mg/y.L. The differences of growth rates and artemisinin contents among hairy roots, untransformated roots and callus were also significant. There were no obvious lag phase in batch culture of hairy roots of Artemisia annua L. The exponential growth phase was 7 approximately 15 days after inculation. The growth rate reached the highest on the 11th day, and the cultures reached a stationary phase on the 20th day. The properties of artemisinin content of hairy roots were obviously "related to growth". The artemisinin content decreased slowly during the exponential phase, increased while the growth rate slowed down and remained consistent after the growth stopped. The optimum culture time for hairy roots of Artemisia annua L. was 21 days in our system.