Change of cold hardiness in bare-rooted Norway spruce planting stock during autumn and its effect on survival

Abstract

The objective of this study was to test a method of measurements of electrolyte leakage for determining an optimal autumn lifting date. The second objective was to obtain information about the effects of different autumn lifting dates on survival of Norway spruce (Picea abies [L.] Karst.) plants. A significant difference was found between lifting dates for the values of root electrolyte leakage (REL) from unstressed plants, but without clear tendency. The values of electrolyte leakage from shoots (SEL) were very stable (11-13%). On the other hand, the electrolyte leakage from roots (REL) decreased in dependence on different lifting date after artificial frost stress. On the first lifting date (end of September) the REL values were 77%. On the last lifting date (8 November) the REL values were 56%. The same tendency was found for SEL values (decrease from 63% at the end of September to 17% on 8 November). Differences were also found in the survival of plants. The plants lifted on earlier dates had nearly 100% mortality, which decreased with later date of lifting. The results of this study showed that cold hardiness of planting stock increased during autumn and was higher for shoots than for roots. The first results showed that it is possible to optimize the autumn lifting date of spruce planting stock by measurements of electrolyte leakage from shoots after artificial frost test.