THE INFLUENCE OF LIGHT QUALITY AND CARBON-DIOXIDE ENRICHMENT ON THE GROWTH AND PHYSIOLOGY OF SEEDLINGS OF 3 CONIFER SPECIES .1. GROWTH-RESPONSES

Plant growth responds to light quality, as evaluated by the red/far-re d (R/FR) quantum flux ratio, and to the level of CO2. Pinus banksiana, Picea mariana and Picea glauca seedlings were raised at 350, 700, or 1050 at mu L . L(-1) CO2 and high or low R/FR ratios and growth was me asured over a 16-week growth period. Far-red rich light enhanced the w hole plant and height relative growth rates of Pinus banksiana. The th ree species showed species specific responses in plant organ relative growth rates and partitioning ratios. On the basis of their biomass pa rtitioning the species would be ranked Pinus banksiana < Picea mariana < Picea glauca for shade tolerance. In commercial operations, seedlin gs grown for outplanting are selected, in part, on the basis of plant form as described by the stem height/diameter ratio. More desirable ra tios were obtained at ambient CO2 concentrations for Pinus banksiana a nd Picea mariana in red rich light and for Picea glauca in far-red ric h light.