The Role of Antioxidant Systems in Cu2+ Stress Resistance in Alternanthera philoxeroides Effect of Cu2+ Stress to the Cell Structure of Two Lichen Species TUNEL Detection of Cu2+ Induced Cell Death of the Phycobionts in Lichen Ramalina sinensis Main and epistasis analysis of QTLs for tolerant to high Cu2+ stress at seedling stage of rice(Oryza Sativa L.)