Effect of handling and water stress on water status and rooting of loblolly pine stem cuttings

Two experiments were conducted to determine the effect of handling, short-t erm storage, and initial water stress on cutting water potential (Psi (W)) and rooting of loblolly pine (Pinus taeda L.) stem cuttings. First, stock p lants and cuttings were measured for Psi (W) at predawn (04:00 a.m.) and ea rly morning (09:00 a.m.). Cuttings were then severed, wrapped in wet paper towels, and placed in insulated containers for 2 or 7 h at approximately 30 degreesC or for 21 h in cold storage (4 degreesC). Water potentials of cut tings were measured at the end of each storage period. Second, effects of i nitial water stress on rooting performance of cuttings were tested by withh olding water from dormant (winter) and succulent (summer) cuttings for vary ing periods of time. After each drying treatment, Psi (W) was measured on a sample of cuttings and the remainder of the cuttings were transferred to a greenhouse with intermittent mist for 12 weeks. Storage of cuttings for long periods (7 to 21 h) of time under low vapor pr essure deficit conditions resulted in less negative water potentials of the cuttings. Dormant cuttings rooted at higher percentages, even after being exposed to lower values of Psi (W) The lower values of Psi (W) in dormant c uttings could be attributed to higher ambient vapor pressure deficit during the drying phase. Results suggest that subjecting cuttings to moderate wat er stress for a short period of time does not adversely affect the rooting of cuttings. Cutting water potentials below -1.7 MPa appeared to reduce roo ting of succulent cuttings and water potentials below -2.0 MPa affected roo ting in dormant cuttings.