Changes in cold hardiness of silver fir and larch bare-rooted seedlings during autumn and spring

Abstract

ABSTRACT:The objective of this study was to obtain information about changes in cold hardiness of larch and silver fir seedlings during autumn and spring by help of measurements of electrolyte leakage from shoots (SEL) and root system (REL). The values of electrolyte leakage from the untreated (control) root system of silver fir decreased during autumn (from 28% on September 25 to 24% on November 27). Minimum values were reached on March 26. A decrease in electrolyte leakage was found for silver fir shoots (SEL) (the maximum was detected on October 2 -12% and minimum on November 27 -7%). Contrary to REL, SEL increased in March. The rate of electrolyte leakage from treated (after artificial frost) roots and shoots decreased during autumn (REL and SEL minimum on November 27). The change in the rate of electrolyte leakage from untreated larch roots was similar to that from silver fir roots during autumn. The values continually decreased from 26% (on September 25) to 12% (on November 27). The course of electrolyte leakage from the treated root system was similar for both species. The differences between electrolyte leakage from larch shoots (treated und untreated ones) were statistically significant, but without any clear tendency during autumn. The objective of this study was to acquire the first information about changes in cold hardiness of larch and silver fir seedlings during autumn and spring by help of measurements of electrolyte leakage from shoots and root system. MATERIALS AND METHODSSilver fir (Abies alba Mill.) and larch (Larix decidua Mill.) seedlings cultivated in a nursery of Forest Research Institute in Zvolen were used in this study. The biometrical characteristics and age of tested planting stock are given in Table 1. Unfortunately, no complex information about plant raising in the nursery is available.Seedlings were lifted at one-week intervals in autumn (from September 25 to November 27) and in spring (two sample dates, March 12 and 26). On each occasion 30 seedlings were lifted. Directly after lifting the seedlings were checked carefully and only plants without mechanical damage were used (untreated seedlings). Samples of shoots and roots were taken from 15 plants to prepare the procedure of electrolyte leakage measurement. The remaining 15 plants were transported to a lab of Forest Research Institute in Zvolen and used for cold hardiness tests. These whole plants were placed in polyurethane bags and to a refrigerator (temperature 2°C). After two hours, the plants were put to a climatic room for 20 hours (temperature -16°C). After this artificial frost treatment and one hour in the room temperature samples from roots and shoots were taken for electrolyte leakage measurement (treated seedlings). 239The modified method according to McKAY (1992) was used for all electrolyte leakage measurements. The root system was washed in cold tap water to remove soil and rinsed in deionized water to remove surface ions. The sample length from main root (taken directly under the root collar) and shoot (taken di...