Eva Stattin

Cold Acclimation and Deacclimation of Shoots and Roots of Conifer Seedlings

Conifers that are adapted to grow in regions where marked annual temperature changes are observed have developed physiological mechanisms that enable them to alternate their growth and rest periods in phase with the climate, so they exhibit a strong periodicity in cold hardiness. Cold acclimation is the transition from a non-hardy state to a hardy one. It is a complex physiological process that enables plant tissues to become tolerant to extracellular freezing, duration of cold and also to temporal thawing (Levitt 1980). The annual growth rhythm of trees and the ability to cold harden are determined genetically (Weiser 1970) but are controlled by environmental cues (Levitt 1980).

Mini-seedlings of Picea abies are less attacked by Hylobius abietis than conventional ones : is plant chemistry the explanation?

Abstract The pine weevil, Hylobius abietis (L.), is a major pest in conifer reforestation areas in the Palaearctic region. Size and chemistry of the seedlings may explain the damage rates in plantations. The performance of 10-week containerized seedlings (mini-seedlings) was compared with 1-year-old conventional seedlings of Norway spruce, Picea abies (L.), in a field experiment in central Sweden. After 2 years the weevil damage was lower for the mini-seedlings than for the conventional seedlings (3.5 vs 55%). After 3 years, the overall survival was 82 and 75%, respectively. Weevil damage was the main cause of mortality for conventional seedlings, whereas mini-seedlings mainly died from drought. Volatiles of the two seedling types were compared by solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS). Unwounded mini-seedlings and conventional seedlings differed in their compositions of monoterpenes and sesquiterpenes. Mini-seedlings mainly emitted limonene, known to be repellent to the pine weevil. When wounded, green leaf volatiles were released by mini-seedlings while the pine weevil attractant α-pinene was released by conventional seedlings. Volatiles may partly explain the mini-seedlings’ resistance against weevil attack. Further studies are needed to clarify how long this mini-seedling effect remains.

Storability measures of Norway spruce and Scots pine seedlings and assessment of post-storage vitality by measuring shoot electrolyte leakage

As indoor frozen storage is increasing in forest tree nurseries it is important to have accurate methods for assessing seedling storability in autumn and methods to determine post-storage vitality. Storability of spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.) seedlings can be based on determination of dry matter content (DMC) of seedling shoots or by freezing shoots at –25°C and thereafter measure electrolyte leakage (SELdiff–25). To compare these two methods we stored 1-year-old spruce and pine seedlings at different occasions during the autumn. To test if leakage of electrolytes from shoots (SEL) could indicate deteriorated vitality, we measured SEL at the end of storage. After storage seedling viability was determined in a three-week growth test, measuring shoot and root growth capacity (RGC). Determination of freezing tolerance (SELdiff–25) before storage had a better ability to predict the outcome of storage compared to the DMC test. Measuring SEL at the end of the frozen storage period accurately indicated seedling vitality. Seedlings with SEL of 0–5% had a high survival rate whereas SEL over 10% indicated low survival and growth capacity after storage. The SEL method has a potential to become a screening test for identifying batches of seedlings that have been damaged during storage in the nursery.