Doctoral defense Public defense of Ewout Van Oost


Title: "Identification of determinant parameters for frost tolerance in Lavandula spp."

Summary of the dissertation

Due to climate change and the predicted increase in summer dry periods, the demand for drought tolerant garden plants, especially lavender, has markedly risen. The successful establishment of lavender in temperate or cold climate regions is however problematic due to a lack of winter hardiness among most species. This research focused on studying physiological, biochemical, and anatomical characteristics of lavender to better understand and improve frost tolerance. Therefore, in a collection of 84 different lavender species and cultivars, differences in frost tolerance were investigated through field observation, controlled freezing experiments, the measurement of cell sap leakage and analysis of photosynthetic disruption. The results indicated that the survival temperature ranged from 19,4 °C in the most frost tolerant species to 2,9 °C in the most sensitive species. The leaf water content proved to be a determinant factor, as frost tolerant plants consistently had a lower leaf water content than frost sensitive plants. Seasonal changes in leaf water content were correlated with the acquisition of frost tolerance during cold acclimation. Freezing temperatures caused irreversible damage to the photosystem in frost sensitive lavender species and also induced
embolisms (i.e. air bubbles) in the xylem conduits (i.e. water transporting channels in the stem) of these species, hampering water uptake and causing the plants to wilt. A genetic screening of the lavender collection allowed to identify opportunities to enhance winter hardiness in lavender by crossbreeding of different species. The results of this research will support the future development of more resilient garden plants with improved winter hardiness.

Possibility to follow online through MS Teams.

You are kindly invited to a reception after the defense. Please confirm your attendance before January 20th 2024.