Abstract Rooting of adventitious shoots of western white pine ( Pinus monticola ) continuously exposed to a variety of growth regulators for 6 weeks varied between 0 and 20 percent. Pulse treatment of similar shoots for 7 days with the same growth regulator treatments followed by 5 weeks culture on medium devoid of growth regulators provided 40-64 percent rooting. In paired comparisons, pulse treatments always provided better rooting percentages than did constant exposure treatments. Improved root growth and the initiation of multiple roots were also favored by pulse treatments. Forest Sci. 28:822-825.
Amerson et al. (Wed,) studied this question.