Photosynthetic efficiency of frozen-stored Picea glauca seedlings in relation to root pruning, root growth, and shoot moisture stress / by S. J. Colombo. --

Abstract

This study examines the influence of duration of frozen storage (-2 C) and root pruning on photosynthetic efficiency, shoot moisture stress and root growth of white spruce (Picea glauca (Moench) Voss) seedlings planted in a glasshouse. Photosynthetic efficiency was measured using infra-red gas analysis, and shoot moisture stress by the pressure chamber technique. Root growth was determined using trees planted in glass-faced root boxes. Photosynthetic efficiency of root pruned and non-pruned trees which were not frozen was significantly greater 2 and 4- weeks after planting than that of stock frozen 92 days. Rates of photosynthesis of trees which had been frozen for 50 days were inexplicably lower than other storage treatments up to four weeks after planting. After six weeks photosynthetic efficiency was high regardless of duration of storage. Shoot moisture stress of seedlings stored 92 days remained significantly greater than non-frozen stock throughout the experiment, in spite of greater root growth by those frozen 92 days. Root pruning had a detrimental influence on all aspects of seedling physiology examined: photosynthetic efficiency was lower, shoot moisture stress greater and root growth was slower than in non-root pruned seedlings. Root growth was not strongly correlated with photosynthetic efficiency.