The seedlings and pieces from walnut of 20 years were selected as experiment matrials. The experiment systematically studied such stages during the tissue culture of walnut as getting explants, building aseptic propagation lines, multiplicative propagations, rooting and transplanting. And discussed some key methods such as sterilization and preventing browning. But the contamination and browning of the explants from walnut of 20 years were serious. So the No.of shoots and calli wasn’t meet the needs for sta...