Induction of Near-vessellessness in Ephedra campylopoda C. A. Mey.

Near-vessellessness was induced in the secondary xylem of Ephedra campylopoda C. A. Mey. by mechanical bark blocking or by wounding. Both treatments resulted in regions of near-vesselless xylem. Xylem formed after the mechanical bark blocking also had regions in which the orientation of the axial components was changed from axial to lateral. Since either mechanical arrest of phloem and cambial transport or wounding of the cambium almost stopped differentiation into vessels, and instead induced differentiation into tracheids, it seems that the developmental signal for tracheid differentiation is not the same as that for vessels. The possible regulation of near-vessellessness in Ephedra is discussed. Copyright 1994, 1999 Academic Press