Photosynthetic Performance Of The Holly Ilex Aquifolium L. During Winter In Central Europe: An Ecophysiological Advantage Of Climate Change?

Winter temperature and especially frost are important limiting environmental factors for the distribution of holly (Ilex aquifolium) in Central Europe. I. aquifolium profits already from the contemporary climate change and increases its distribution in Central Europe and at its northern limits in Scandinavia. We studied the importance of mild winter temperature for the physiology of I. aquifolium, especially the acclimatisation of the photosynthesis during mild winters. The photosynthesis was investigated by chlorophyll fluorescence. In mild winters leaves of Ilex showed a very fast recovery of photosynthesis when exposed to room temperature within two hours. While after long-term frost period the photosynthesis was drastic effected and the measured electron transport rates of field-grown Ilex trees were reduced up to 50% compared to the control plants in the greenhouse. The results indicating that the photosynthesis performance in winter and its recovery is influenced by minimum air temperature and frost duration. In general, during winter the evergreen holly was still able to maintain its photosynthesis, to react flexible to frost-free days. Therefore, holly was able to photosynthesise in the understory during mild day in winter and spring, when deciduous trees are leafless, and a sufficient light quantity reaches the soil.