5Biedermann I. E. G. Factors affecting establishment and development of magnolia hybrids in vitro[J].Acta Horticulture , 1987,212 : 625-627.
6Merkle, S.A. , R.J. Sotak, A.T. Wiecko, and H.E. Sommer. Optimization of the yellow-poplar embryogenic system[J]. Proc. 20 th southern For. Tree Imp. Conf. Charleston, S. C. p. , 1989,186-193.