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What it means to be an evergreen: Boreal pine trees have to cope with clear sunny skies and freezing temperatures. We study the physiological, biochemical and molecular mechanisms by which evergreen conifers adjust their photosynthetic machinery to changing environmental conditions in order to avoid photoinhibition and severe damage to the green needle tissue [photo: Ingo Ensminger] Dr. Ingo Ensminger
Global Change & Photosynthesis, Plant Physiology
Projects
Primary Research Results
My recent research focused on the effects of temperature and light on photosynthesis in boreal conifers in Central Siberia This work was pursued in the group of Prof. Lloyd at the Max-Planck-Institute for Biogeochemistry. We observed that the highest degrees of photoprotection occur during early spring in April, when light levels are high and temperatures are still below zero. (Ensminger et al. 2004 in Global Change Biology, Sveshnikov et al. submitted to Tree Physiology). During this transition period a class of “transitory” light induced proteins (Elips) occurs in the thylakoid membrane of the chloroplast, together with complementary changes in other key proteins of the thylakoid membrane. These observations partly contradicted earlier results obtained from conifers from milder climates. In addition, a relatively short time was sufficient to induce major functional changes (photochemical energy conversion, net gas exchange) of the photosynthetic machinery. This gave raise for a new hypothesis, that the winter acclimated chloroplast system is able to respond opportunistically to the changing environment and does not simply represent a winter dormant state. This would have major consequences in respect to anticipated future increases in spring temperatures.
Current and Future Research Directions: PhysConFor
Based on these results we have recently started on a new project “PhysConFor” (Physiology of Coniferous Forests) funded by the Marie Curie Program of the European Union. Through PhysConFor we are planning to develop into the new field of Global Change Molecular Physiology.
Beginning of spring in the Siberian Taiga near Zotino. [ photo:Ingo Ensminger]
Warmer temperatures are likely to increase physiological activity of the northern hemisphere vegetation. But this potentially increased productivity could be counteracted by the effects of changes in seasonal climate pattern. If developmental changes are not sufficiently synchronized with seasonal patterns of climate, this can cause detrimental effects to the conifers, as e.g. frost damage due to a too early dehardening in spring or a delayed hardening in autumn. In addition increased frequency of summer droughts may induce developmental changes or stress responses and alter photosynthesis. In our experiments we use the evergreen conifers Scots pine, Jack pine and White spruce. Our experimental design includes controlled environments (growth chambers) (photo 1 below), experimental field plots (photo 2 below) and sampling at longterm monitoring sites in natural forests (photo 3 below). Using this diverse approach allows us to evaluate our data on different levels of complexity.
 Photo 1: Typical phenotype of 1 year old Jack seedlings after four weeks exposure to different autumn growth conditions in controlled environments [photo:
Florian Busch
] |
 Photo 2: Experimental set up with Scots pine and Jack pine at the UWO field station near London/Ontario [photo: Ingo Ensminger] |
 Photo 3: View from a monitoring tower above the canpoy of a Jack pine forest (Saskatchewan) [photo: Ingo Ensminger] |
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The methods we use include physiological measurements (i.e. photosynthetic gas exchange, chlorophyll fluorescence), biochemical analysis (photosynthetic pigments, carbohydrates, proteins) and gene expression analysis. Using these techniques not only in controlled environments put also in outdoor experiments will improve our mechanistic understanding and help to develop new process based models of photosynthesis, carbon sequestration and forest production.
Florian Busch sampling conifer needles in the field (Saskatchewan) [photo: Ingo Ensminger]
