Photoprotection, not increased growth, characterizes the response of Engelmann spruce (Picea engelmannii) seedlings to high light, even when resources are plentiful


Author for correspondence: A. K. Mitchell Tel: +1250 3630786 Fax: +1250 3636005 Email:


  • • To investigate the effects of resource limitation on the use of light by Engelmann spruce seedlings (Picea engelmannii), we examined the effects of nitrogen (N) supply on growth and physiological acclimation.
  • • Seedlings were grown under a factorial combination of two levels of light (100%, 33% full light) and two levels of N-supply (100 mg l−1 and 10 mg l−1). Biomass, foliage physiology, and pigment composition were measured.
  • • No significant differences were found in growth or photosynthetic capacity between seedlings grown under high and low light, regardless of whether seedlings were grown under conditions of high or low N-supply. Both a decrease in the capacity for light capture and an increase in the capacity for thermal dissipation of excess absorbed light occurred with growth at high relative to low light as well as at low relative to high N-supply.
  • • Damage to foliage from excess light appeared to be avoided through a combination of downward adjustments in chlorophyll and upward adjustments in photoprotective xanthophyll cycle carotenoids.