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Influence of nursery culture on western red cedar
Authors:Raymund S Folk  Steven C Grossnickle  John E Major  James T Arnott
Institution:(1) Forest Biotechnology Centre, British Columbia Research Inc., 3650 Wesbrook Mall, V6S 2L2 Vancouver, B.C., Canada;(2) Pacific Forestry Centre, Forestry Canada, 506 W. Burnside Rd., V8Z 1M5 Victoria, B.C., Canada
Abstract:Western red cedar (Thuja plicata Donn) seedlings were grown in a greenhouse and subjected to six nursery cultural treatments (long-day wet (LDW), long-day moderate (LDM), long-day dry (LDD), short-day wet (SDW), short-day moderate (SDM), and short-day dry (SDD)) during mid-summer. Seedling attributes were measured before fall and spring planting.Short-day and moisture stress treatments reduced shoot but not root growth, resulting in reduced shoot to root ratios. Fall tested LDW seedlings had a higher osmotic potential at saturation and turgor loss point than other treatments. Fall tested short-day seedlings had lower resistance to plant water movement. The LDW seedlings had the greatest new root growth in fall testing, while one of the lowest in spring testing. In the fall, LDW seedlings had the greatest net photosynthesis (Pn) at 25 °C root temperature, with all treatments having a similar decline in Pn as root temperatures decreased to 1 °C. In the spring, all treatments had a similar decline in Pn with decreasing predawn shoot water potential. Moisture stress and short-day nursery cultural treatments applied in mid-summer will not harden western red cedar seedlings for all potential field conditions.Spring, compared to fall, tested seedlings had two times the shoot and three times the root dry weight. Spring tested seedlings had a lower osmotic potential, maximum modulus of elasticity, relative water content at turgor loss point and greater dry weight fraction. Fall, compared to spring, tested seedlings had lower resistance to plant water movement and greater cuticular transpiration. In general, fall tested seedlings had more root growth than spring tested seedlings. Spring, compared to fall, tested seedlings generally had greater stress resistance.
Keywords:nursery cultural treatment  seedling quality assessment  western red cedar
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