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Cold stress is one of the most common abiotic stresses experienced by plants and is caused by low temperature extremes and variations. Polyamines (PAs) have been reported to contribute in abiotic stress defense processes in plants. The present study investigates the survival and responses of PA-treated non-acclimated (N) and acclimated (A) winter oilseed rape to increasing cold conditions. The study was conducted under controlled conditions. Seedlings were foliarly sprayed with spermidine (Spd), spermine (Spm), and putrescine (Put) solutions (1 mM) and exposed to four days of cold acclimation (4 °C) and two days of increasing cold (from −1 to −3 °C). Two cultivars with different cold tolerance were used in this study. The recorded traits included the percentage of survival, H+-ATPase activity, proline accumulation, and ethylene emission. Exogenous PA application improved cold resistance, maintained the activity of plasma membrane H+-ATPase, increased content of free proline, and delayed stimulation of ethylene emission under increasing cold. The results of the current study on winter oilseed rape revealed that foliar application of PAs may activate a defensive response (act as elicitor to trigger physiological processes), which may compensate the negative impact of cold stress. Thus, cold tolerance of winter oilseed rape can be enhanced by PA treatment.

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Abstract:Tree genetic diversity is among the most important factors determining the sustainability of forest ecosystems. The main aim of the present study was to track possible changes in genetic diversity of regenerating populations of Norway spruce (Picea abies (L.) H. Karst) and Scots pine (Pinus sylvestris L.) in areas subjected either to a natural disturbance (windthrows and subsequent clear-cutting of the affected spruce stand) or to a changed land-use legacy (pine regeneration on abandoned agricultural land) with the aim of testing whether the new forest generation retains the genetic diversity of the putative maternal stand. Eight highly polymorphic microsatellite loci were used to reveal the genetic diversity and its spatial distribution in the studied tree populations. Self-regenerating juveniles of Norway spruce and Scots pine were spatially random and as genetically diverse as in the putative maternal populations. Genetic differentiation between putatively maternal trees and regenerating juveniles was low for both species. A high genetic diversity and random spatial genetic structure revealed in the regenerating populations provides a basis for the formation of evolutionary and ecologically sound stands able to adapt to ever-changing climatic conditions. Information on the genetic dynamics of the studied natural populations of long-lived coniferous tree species may be important for evaluating possible changes in genetic diversity at a local scale following forest ecosystem disturbances and changes in land-use legacies.