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.
SUMMARY
A study is presented of the growth of rooted cuttings of Lodgepole pine and Sitka spruce into waterlogged soil. Lodgepole pine roots penetrated to depths of 20 cm at 10°C in soil devoid of oxygen, whereas Sitka spruce made only shallow growth into the water‐table. The growth rate of the pine roots decreased with depth below the water‐table and penetration was greater at 10 °C than at 20 °C. Large gas‐filled cavities were found in the stele of the pine roots that penetrated the water‐table but were absent from the spruce. When pine roots were allowed to grow into a water‐table for 2 cm. and were subsequently inundated to a depth of 10 cm, root tip survival was much better than where non‐acclimatized roots were flooded.
The results suggest that the deeper penetration of waterlogged soil by Lodgepole pine than Sitka spruce is due to internal oxygen transport in the pine roots; oxygen transport and other possible mechanisms for growth and survival of roots in waterlogged soil are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.