Morphological and physiological characteristics of air-slit containerized white spruce seedlings (1 + 0) in response to four different irrigation regimes

Air-slit containerized (IPL 25-350A) white spruce seedlings [Picea glauca (Moench.) Voss] were grown in a tunnel under four different irrigation regimes (IR-15%, IR-30%, IR-45% and IR-60%, v/v) during their first growing season. Irrigation regime had a significant effect on seedling morphology, rate of cuticular transpiration, epicuticular wax structure, kinetics of terminal bud formation and the number of needle primordia formed. Water relation variables were not significantly affected by irrigation regime. The density of wax covering the needle surface was inversely related to the moisture content in the rhizosphere. No relationship was found between the amount of wax on the needle surface and the rate of cuticular transpiration. The results of this study will enable nursery managers to attain the desired morphological and physiological characteristics for containerized seedlings through the development of an irrigation strategy.