Inhibition and Requirement of Natural Stimulator for Cambial Xylem Production in Isolated Stem Segments of Pinus silvestris

Formation of xylem in sterile culture of isolated pine stem segments supplied with synthetic media continues only for 4–6 weeks. The stem segments originally do not contain an eluable inhibitor affecting elongation in the test of pine hypocotyl sections. After 4 weeks inhibition is detected. Supplying the medium with a methanolic extract from the cambial region of pine stem prolongs xylem production up to 15 weeks. IAA interacts synergistically with a natural stimulator of cambial activity.