A Pharmacognostical Study on Herba Spirodelae and Its Adulterants A EXPLORATION OF THE PHOTOPERIODIC INDUCTION OF LEMNA MINOR L.──TEST OF COMPARISON WITH LEMNA PAUGIGOSTATA 6746 Damage to DNA Primary Structure and Antioxidant Enzymes in Lemna minor Induced By Hg2+(in English) The Sensitivity of Chloroplast Ultrastructure of Two Duckweed Species to Simulated Acid Rain Changes of nuclear ultrastructure,nDNA and antioxidant enzymes in leaves of Lemna minor induced by Cd2+