Monitoring water and nitrogen stress-induced senescence through NMR relaxometry in oilseed rape

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE

International audience

English. We have recently shown that Nuclear Magnetic Resonance (NMR) relaxometry represented an accurate means to describe water distribution and status at the cellular level and to follow leaf structural changes associated with senescence process. For instance variation in the relative intensities and transverse relaxation times of the NMR signal components associated with vacuole water was positively correlated with water uptake and cell enlargement occurring in parenchyma layer of senescing leaf. Such approach can be used to assess carbon and nitrogen recycling processes in relation to water and nitrogen use efficiency in oilseed rape. In the present study, effect of drought and nitrogen depletion on water distribution among senescing leaf tissues was investigated. Plants (Brassica napus L. cultivar Aviso) were grown under glasshouse conditions in 4L pots filled with high (N+) or low (N-) nitrogen content soil. At pod set, N+ plants were kept well watered or water stressed for three weeks by stop watering and harvested triweekly over the water shortage period. Measurements were performed at different leaf ranks. Physiological status and stress were followed by measuring chlorophyll content, photosystem II activity, stomatal conductance, relative water content and water and osmotic potential. NMR relaxometry and light microscopy were used to describe water distribution and status and corresponding structural organization at the cellular levels. It was possible to detect slight variations in the evolution of water distribution during senescence and to show the effect of nitrogen and water stress. The results are discussed from the perspective of development of a tool for plant phenotyping for oilseed rape growing under environmental stress.