Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants

Drought is the main abiotic stress worldwide affecting harvest quality and quantity of numerous crops. To enable better water management, low field NMR (nuclear magnetic resonance) relaxometry was assessed as a developmental marker and a new method for early detection of water deficiency. The effect of a foliar biostimulant against water stress was also investigated. Two leaves of different ranks (four and eight) were studied. The leaves of different ranks were characterized by different NMR T-2 spectra which validated the ability of NMR to describe the developmental stage of tobacco. Results also showed that T-2 NMR relaxation spectra allow the detection of mild water stress (80% of the field capacity) through the precise characterization of the leaf water status while other water stress markers (relative water content, photosynthetic related parameters...) were not yet impacted. The agricultural impact of the mild water stress was determined through the nitrogen rate in shoots and amino acids assay six weeks after the beginning of the stress and results shows that foliar application of biostimulant limits the negative consequences of drought. Our results demonstrate the sensitivity of NMR to detect slight changes triggered in the leaf by water stress at the tissue level.