Bioeffect Comparison of Mutation Induction by Mixed High Energy Particle Field and γ-rays Irradiation in Alfalfa ’Longmu 803’ SSR ANALYSIS ON M_1 VARIATION OF WHEAT IRRADIATED BY MIXED HIGH ENERGY PARTICLE FIELD Effect of Mixed High-energy Particles Field on Corn Seedling Growth and the Activity of Antioxidant Enzymes Effects on cold tolerance of M2 of Longmu No. 803 alfalfa seed pre-treatedwith a mixed high-energy particle field