Mist level influences vapor pressure deficit and gas exchange during rooting of juvenile stem cuttings of loblolly pine

Abstract

Two experiments were conducted during which juvenile hardwood or softwood stem cuttings of loblolly pine (Pinus taeda L.) were rooted under six mist regimes in a poly-ethylene-covered greenhouse to investigate the effect of mist level on vapor pressure deficit (VPD) and cutting water potential (Ψcut), and to determine the relationships between these variables and rooting percentage. In addition, net photosynthesis at ambient conditions (Aambient) and stomatal conductance (gs) were measured in stem cuttings during adventitious root formation to determine their relationship to rooting percentage. Hardwood stem cuttings rooted ≥80% when mean daily VPD between 1000 and 1800 HR ranged from 0.60 to 0.85 kPa. Although rooting percentage was related to Ψcut, and Aambient was related to Ψcut, rooting percentage of softwood stem cuttings was not related to Aambient of stem cuttings. Using VPD as a control mechanism for mist application during adventitious rooting of stem cuttings of loblolly pine might increase rooting percentages across a variety of rooting environments.