Effects of light quality on plant acclimation and production of tree seedlings

Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) are the most predominant and economically important tree species in Sweden and Scandinavia. The production of tree seedlings of these species is key for the regeneration of Swedish forests. However, seedlings of these conifers, when grown in forest nurseries, often lack acclimation to high light and high ultraviolet (UV) irradiance present in sunlight. This can lead to photoinhibition and damage of their photosynthetic apparatus, ultimately impeding their growth, fitness, and survival, thus hindering their production. To address this critical issue, the proposed HÖG project aims to use UV and visible light to improve Norway spruce and Scots pine seedling acclimation, reducing damage from high light and UV stress in commercial plant production. UV radiation isn't solely harmful to plants; low levels of UV perceived by the UVR8 photoreceptor trigger photomorphogenic responses and help plants alleviate damage induced by oxidative stress. Yet, the mechanisms by which UV and other light signaling pathways promote acclimation in conifer tree seedlings are not well-understood. Here, we hypothesize that UV treatments triggering the UVR8 pathway will enable these two important conifers tolerate the challenges posed by high light stress. We also aim to formulate spectral treatments that promote the growth and long-term fitness of Norway spruce and Scots pine. To achieve these goals, we will design factorial experiments to examine the effects of various wavebands within the UV region of the spectrum on several plant responses. Whole transcriptome changes induced by different light treatments will be assessed through RNA-seq and changes metabolite profiles through Ultra high performance liquid chromatography. Morphological parameters, accumulation of antioxidants and photosynthetic performance will also be measured. Moreover, we will investigate the impact of genetic variation within these species and identify candidate genes involved in high light and UV stress acclimation. This project gathers a collaborative team with expertise in light signaling from Örebro University, lighting technology from Heliospectra AB, and forest tree seedling physiology and production from Svenska Skogsplantor. The project's expected outcomes have the potential to provide groundbreaking insights into how integrating UV radiation with other light signaling pathways affects the acclimation of Norway spruce and Scots pine. The data generated could be a valuable foundation for indoor cultivation of hardier tree seedlings, potentially revolutionizing our understanding of UV and light signaling in these conifers, with significant benefits for indoor tree seedling cultivation.