AgreenSkills session, year: 1st session, 2015
Receiving laboratory: EGFV Ecophysiology and Grape Functional Genomics Bordeaux Aquitaine
Country of origin : Austria
Impacts of water stress on forest and agro-ecosystems: understanding and modeling key mechanisms of drought tolerance
Adaptation to climate change, and specifically water stress, is one of the most important topics in plant biology. Water stress reduces plant growth and crop yield, and for perennial crop and tree species there is an added consideration; their long-term ability to tolerate and recover from stress. A species’ resilience truly embodies two attributes: (1) the means to maintain productivity over the short term under stress, (2) the long term ability to recovery from periods of severe stress. The ideal for a plant is to maximize both of these attributes. This project will quantify the resilience of various winegrape and forest tree species through elucidating whole plant relationships of the loss and recovery of hydraulic capacity in response to water stress. These experiments will identify particular winegrape and tree species with an increased ability to tolerate and recover from this stress. Finally, these results will be used to model the extent to which water stress will reduce water uptake and gross ecosystem productivity in these ecosystems.
I am a tree ecophysiologist, whose research interest focuses on the impact of abiotic stress on plant physiology and respective avoidance and adaptation strategies. Resistance to abiotic stress is a key factor limiting productivity, survival and distribution in many agro-ecosystems. Whereas most studies are restricted to one particular aspect, I aimed to embrace all processes involved in stress resistance (e.g. loss of xylem hydraulic conductivity and repair, cellular damages, bud dormancy, physiological determinism, hydraulic vulnerability segmentation).
Although during my early carrier, I used destructive methods to assess the impact of freezing stress on living cells (frost acclimation, dormancy release and related physiology) and xylem components (winter embolism ad repair) in different tree species, I focused on the use of non-destructive methods to monitor abiotic stress.
New insights were especially enabled by ultrasonic emission analysis, which was used to study ice nucleation and propagation, cavitation during and after freeze-thaw cycles, as well as for monitoring of cell damages. My findings improved our knowledge of freezing and thawing in plants and led to a general framework of involved processes: During freezing, cavitation and water fluxes are induced by the low water potential of the ice front. On thawing, enclosed bubbles may expand while potential gradients caused by transpiration and/or remaining ice blockages cause further cavitation. Overall, drought- and frost-induced cavitations are based on surprisingly similar mechanisms, and accordingly, resistance to drought and freezing were found to be interlinked.
During my Agreenskills project, I applied my background to study grapevine’s water relations, unraveling the confusion surrounding its hydraulic behavior under drought. I defined water stress thresholds for specific physiological events, such as stomatal closure, stem embolism, and leaf mortality.
1. Charrier G.*, Nolf M.*, Leitinger G., Charra-Vaskou K., Tappeiner U., Améglio T., Mayr S. Freezing in timberline trees: a simple phase shift causes complexity. Plant Physiology (doi:10.1104/pp.16.01815).
2. Charrier G., Chuine I., Bonhomme M., Améglio T., Assessing frost damages using dynamic models in walnut trees: exposure rather than vulnerability controls frost risks. Plant, Cell and Environment (doi:10.1111/pce.12935).
3. Charrier G., Torres-Ruiz J.M., Badel E., Burlett R., Choat B., Cochard H., Delmas C.E.L., Domec J.C., Jansen S., King A., Lenoir N., Martin-StPaul N., Gambetta G.A., Delzon S. 2017. High resolution X-ray microtomography provides evidence for hydraulic vulnerability segmentation, and lack of refilling under tension in grapevine. Plant Physiology 172:1657–1668 (doi:10.1104/pp.16.01079).
4. Guàrdia M., Charrier G., Vilanova A., Savé R., Ameglio T., Aletà N. Genetics of frost hardiness in Juglans regia L. and relationship with growth and phenology. 2016. Tree Genetics & Genomes 12: 83 (doi:10.1007/s11295-016-1038-3).
5. Lens F., Vos R., Charrier G., van der Niet T., Merckx V., Baas P., Aguirre Gutierrez J., Jacobs B., Chacon Dória L., Smets E., Delzon S., Janssens S. 2016. Scalariform-to-simple transition in vessel perforation plates triggered by differences in climate during the evolution of Adoxaceae” Annals of Botany 118: 1043-1056 (doi: 10.1093/aob/mcw151).
6. Chuine I., Bonhomme M., Legave J.M., Garcia de Cortazar-Atauri I., Charrier G., Lacointe A., Améglio T. 2016. Can phenological models predict tree phenology accurately in the future? The unrevealed hurdle of dormancy break. Global Change Biology 22: 3444–3460 (doi: 10.1111/gcb.13383).
7. Charra-Vaskou K., Badel E., Charrier G., Mayr S., Améglio T. 2016. The dynamics of embolism formation in trees during freeze-thaw cycles. Journal of Experimental Botany 67, 739-750 (doi: 10.1093/jxb/erv486).
8. Charrier G., Ngao J., Saudreau M., Améglio T. 2015. Effects of environmental factors and management practices on microclimate, winter physiology and frost resistance in trees. Frontiers in Plant Science 6, 259 (doi: 10.3389/fpls.2015.00259).
9. Charrier G., Pramsohler M., Charra-Vaskou K., Saudreau M., Améglio T., Neuner G., Mayr S. 2015. Ultrasonic emissions during ice nucleation and propagation in plant xylem. New Phytologist 207, 570-578 (doi: 10.1111/nph.13361).
10. Kasuga J., Charrier G., Uemura M., Améglio T. 2015. Characteristics of ultrasonic acoustic emissions from walnut twigs during freeze-thaw-induced embolism formation. Journal of Experimental Botany 66, 1965-1975 (doi: 10.1093/jxb/eru543).
11. Charrier G.*, Charra-Vaskou K.*, Kasuga J., Cochard H., Mayr S., Améglio T. 2014. Freeze-thaw stress. Effects of temperature on hydraulic conductivity and ultrasonic activity in ten woody angiosperms. Plant Physiology 164: 992-998 (doi:10.1104/pp.113.228403).
12. Charrier G., Charra-Vaskou K., Legros B., Améglio T., Mayr S. 2013. Changes in ultrasound velocity and attenuation indicate freezing of xylem sap. Agricultural and Forest Meteorology, 185: 20-25 (doi:10.1016/j.agrformet.2013.10.009).
13. Charrier G., Poirier M., Bonhomme M., Lacointe A., Améglio T. 2013. Frost acclimation in different organs of walnut trees Juglans regia L.: How to link physiology and modelling? Tree Physiology 33: 1229-1241 (doi:10.1093/treephys/tpt090).
14. Charrier G., Cochard H., Améglio T., 2013. Evaluation of the impact of frost resistances on potential altitudinal limit of trees. Tree Physiology 33: 891–902 (doi:10.1093/treephys/tpt062).
15. Charra-Vaskou K.*, Charrier G.*, Wortemann R., Beikircher B., Cochard H., Améglio T., Mayr S. 2012. Drought and frost resistance of trees: a comparison of four species at different sites and altitudes. Annals of Forest Science. 69: 325-333 (doi 10.1007/s13595-011-0160-5).
16. Charrier G., Bonhomme M., Lacointe A., Améglio T. 2011. Are budburst dates, dormancy and frost acclimation in walnut trees mainly under genotypic or environmental control? International Journal of Biometeorology. 55: 763–774 (doi:10.1007/s00484-011-0470-1).
17. Charrier G., Améglio T. 2011. The timing of leaf fall affects cold acclimation by interactions with air temperature through water and carbohydrate contents. Environmental and Experimental Botany. 72: 351-357 (doi:10.1016/j.envexpbot.2010.12.019).
2012 – Silver medal from the French Academy of Agriculture