CHANGES IN WATER AND CARBOHYDRATE STATUS OF THREE NURSERY SPECIES IN CONTAINERS DURING OVERWINTER STORAGE IN THREE ENVIRONMENTS
During overwinter storage in an open coldframe, a shaded single-layer polyhouse, and an unshaded double-layer polyhouse, changes in water potentials, moisture content, soluble sugars, and starch were compared in shoots of Colorado spruce (Picea pungens Egnelm.) and Ramlosa juniper (Juniperus sabina L. ’Ramlosa’), both container-grown for one season, and also of globe cedar (Thuja occidentalis L. ’Woodwardii’), field-potted 1 mo prior to testing. Higher water status and higher sugar and starch content were observed in all species in the polyhouse than in the coldframe. Differences between effects of the polyhouses were less clear-cut. During the storage period, higher water status and higher soluble sugars were generally observed in spruce than in juniper and cedar. The sugar to starch ratio (an index of metabolic activity) remained relatively constant for juniper and cedar but decreased during the period of storage for spruce. Extent of winter injury, as indicated by post-winter storage conditions of plants, was 10 and 40% less for cedar and juniper, respectively, overwintered in the polyhouses than in the coldframe; spruce survived equally well in all three environments.