Sammendrag
Environmental changes such as early spring and warm spells induce photosynthetic processes in cold-acclimated coniferous trees and consecutively, cellular metabolism. The purpose of the study was to examine metabolism in conifers under forced deacclimation (artificially induced spring) by exposing twigs of Picea abies and Abies alba to a greenhouse environment (22 °C, 16/8 h D/N cycle). Besides scoring of bud opening, GC/MS–based metabolite profiling was utilized in order to describe metabolic changes in needles and buds during the consecutive trial period of 9 weeks. More than 30 metabolites were identified comprising compound groups such as mono- and disaccharides, TCA acids and amino acids, phenols and phosphorylated structures. Multivariate statistical analyses (Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA)) were applied to visualize segregation patterns related to the stage of tissue deacclimation, tissue type, and between species. In comparison to buds, needles of both species indicated relatively strong and positive correlation of hexoses and pentoses (fructose, glucose, galactose, ribose and arabinose) and phosphoric acid with bud opening score. Moreover, sugar alcohols (arabitol and mannitol) were also positively correlated with bud opening score in P. abies. In contrast, major disaccharides such as maltose, sucrose and melibiose (P. abies) were negatively correlated with bud opening. In general, PCA clearly described segregation patterns between tissue types (buds and needles) and species (P. abies and A. alba). However, statistical analyses suggested, with a few exceptions in A. alba, similar metabolite profiles in needles in both species as compared to buds. This study has shed light on how temperature affects metabolism in buds and needles during the process of deacclimation in general, and contributes to the discussion about how phenological characters in conifers may respond to future global warming.
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