## 3 Results
### NMR Monitoring of Mild Drought Stress  
The distribution of water proton T\({}_{2}\) in the leaf shown in Figure 3a was a general feature of NMR spectra obtained for the leaves of the two leaf ranks under the different treatments at the two stages. This spectrum describes the distribution of the NMR transverse relaxation times of water molecules in leaf tissue and the surface area of each peak is directly related to the specific water fraction and can be expressed in g of water per leaf area in m\({}^{2}\). All T\({}_{2}\) distributions presented three distinct peaks; the first one centered around 18 ms, the second one centered between 100 to 150 ms, and the last one centered between 250 ms for LR 8 and 500 ms for LR 4. The two leaves rank studied presented different T\({}_{2}\) and LWW for all conditions. At both stages and for all peaks, the T\({}_{2}\) is always longer for older leaves (LR4) than the mature one (LR8) (Figure 4). The developmental stage of leaves mainly affected the last peak of the spectrum. The T\({}_{2}\) value of the third peak increased with the age of the leaf. Figure 3b) shows the correlation between relative intensities of the second (RI-2) and third peaks (RI-3) (expressed as a percentage of the total signal). This high correlation represented by these two peaks reflects the strong interaction involving a diffusional process between the two water compartments. The correlation between RI-2 and RI-3 was observed in both leaf ranks studied, showing that the interaction between water pools was not affected by the age of the leaf. Nevertheless, a clear difference in water distribution was observed between the two leaf ranks during plant development. Indeed, the relative intensity of the third peak IR-3 decreased between stages for LR 8, and increased in older leaves (LR 4) confirming that two different developmental processes were occurring in the two leaves studied. The values of the T\({}_{2}\) and intensity (expressed in water g\(\cdot\)m\({}^{-2}\)) of each peak as a function of the different treatment are presented in Figures 4 and 5. \begin{table}
\begin{tabular}{c c c c c} \hline
**Leaf** & **Treatment** & **FW per Leaf Area** & **FW per Leaf Area** & **DW per Leaf Area** & **DW per Leaf Area** \\
**Rank** & **Treatment** & **42 DAS** & **57 DAS** & **42 DAS** & **57 DAS** \\ \hline \multirow{3}{*}{**4**} & **Control** & 72.8 \(\pm\) 5.6 \({}^{\text{a,1}}\) & 76.3 \(\pm\) 2.1 \({}^{\text{a,1}}\) & 2.55 \(\pm\) 0.15 \({}^{\text{a,1}}\) & 2.55 \(\pm\) 0.45 \({}^{\text{a,1}}\) \\  & **Stress** & 72.6 \(\pm\) 2.5 \({}^{\text{a,1}}\) & 77.1 \(\pm\) 0.2 \({}^{\text{a,2}}\) & 2.41 \(\pm\) 0.15 \({}^{\text{a,1}}\) & 2.61 \(\pm\) 0.09 \({}^{\text{a,2}}\) \\  & **Stress-Ti** & 76.2 \(\pm\) 5.3 \({}^{\text{a,1}}\) & 80.7 \(\pm\) 7.4 \({}^{\text{a,1}}\) & 2.88 \(\pm\) 0.43 \({}^{\text{a,1}}\) & 3.12 \(\pm\) 0.20 \({}^{\text{b,2}}\) \\ \hline \multirow{3}{*}{**8**} & **Control** & 36.6 \(\pm\) 0.6 \({}^{\text{b,1}}\) & 49.6 \(\pm\) 6.4 \({}^{\text{b,2}}\) & 2.65 \(\pm\) 0.12 \({}^{\text{a,1}}\) & 2.53 \(\pm\) 0.22 \({}^{\text{a,1}}\) \\  & **Stress** & 40.4 \(\pm\) 3.6 \({}^{\text{b,1}}\) & 45.7 \(\pm\) 4.3 \({}^{\text{b,1}}\) & 2.60 \(\pm\) 0.20 \({}^{\text{a,1}}\) & 2.77 \(\pm\) 0.16 \({}^{\text{a,1}}\) \\ \cline{1-1}  & **Stress-Ti** & 40.5 \(\pm\) 3.6 \({}^{\text{b,1}}\) & 52.0 \(\pm\) 4.7 \({}^{\text{b,2}}\) & 2.42 \(\pm\) 0.14 \({}^{\text{a,1}}\) & 2.92 \(\pm\) 0.06 \({}^{\text{b,2}}\) \\ \hline \end{tabular}
\end{table} 
Table 2: Fresh Weight per leaf area (FW) and Dry Weight per leaf area (DW) of the LR4 and LR8 at two stages and for different treatments. Different letters means statistical differences (\(p\) \(<\) 0.05) between treatments or leaf ranks and different numbers means statistical differences (\(p\) \(<\) 0.05) between stages for the same leaf.