Root growth in Sitka spruce and Douglas-fir transplants: dependence on the shoot and stored carbohydrates

Abstract

When dormant Sitka spruce (Picea sitchensis (Bong.) Carr.) transplants were lifted from the nursery in March and transferred to favorable growing conditions in a controlled environment chamber, new roots emerged and elongated even when the plants were bark-ringed so that the roots could not receive metabolites from the shoot by phloem translocation. Carbohydrate analysis showed that starch reserves in the roots of the bark-ringed plants were depleted, indicating that these reserves provided the energy source for new root growth. The shoot also had a role in new root growth as excised root systems showed greatly reduced root growth. This response is compared to that of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in which bark-ringing prevented root growth indicating that current photosynthate is needed for new root growth. The findings are discussed in relation to the problems of establishing these species in forest plantations.