## 3 Results and Discussion  
Are the Morpho-Physiological Responses to Individual Stresses Different from the Combined Ones? Are Additive, Synergistic or Antagonistic Effects in the Combined Stress? The morpho-physiological results clearly indicated an opposite pattern in the response of the tomato plants to the single stresses with the ABIO treatment showing a more negative impact than the BIO one with respect to the CTR plants (Figures 1 and 2). In particular, the LFW, LDW, LWC, A, and iWUE were significantly reduced in the ABIO plants with respect to the control, whereas no significant differences were observed in the presence of herbivory except than for leaf water content and iWUE (Figures 1 and 2; Tables 1 and 2). Figure 1: Morphological traits. Leaf fresh (g), dry weight (g) and leaf water content (%) of tomato plants treated with different stress: drought stress plus N deficiency (ABIO), infestation by the insect _Tuta absolute_ (BIO) and their combination (COMB) for different times of exposure (0, 1, 3 and 8 days). Unstressed control plants (CTR). Each value and its error bar indicate the mean and the standard error of the mean, respectively (N = 4). Figure 2: Gas exchange parameters. Photosynthetic rate (\(\mu\)mol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-1}\)), stomatal conductance (mol H\({}_{2}\)O m\({}^{-2}\) s\({}^{-1}\)), transpiration rate (mmol H\({}_{2}\)O m\({}^{-2}\) s\({}^{-1}\)) and intrinsic water use efficiency (\(\mu\)mol CO\({}_{2}\) mol\({}^{-1}\) H\({}_{2}\)O) of the leaves of tomato plants treated with different stress for different time of exposure (0, 1, 3 and 8 days). Acronyms as in Figure 1. Each value and its error bar indicate the mean and the standard error of the mean, respectively (N = 4). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multirow{2}{*}{**Statistics**} & \multicolumn{6}{c}{**Time (Ti)**} \\ \cline{3-7}  & & **Treatments (Tr)** & **t0** & **t1** & **t3** & **t8** \\ \hline \multirow{4}{*}{\begin{tabular}{c} Photosynthetic rate \\ \end{tabular} } & Tr 17.60 *** & ABIO & a & b & bc & ab \\ \cline{2-7}  & Ti 2.73 \({}^{\text{NS}}\) & BIO & a & a & a & ab \\ \cline{2-7}  & BI 20.74 *** & COMB & a & b & c & b \\ \cline{2-7}  & TrxTi 0.76 \({}^{\text{NS}}\) & CTR & a & ab & ab & a \\ \hline \multirow{4}{*}{\begin{tabular}{c} Stomatal conductance \\ \end{tabular} } & Tr 5.38 *** & ABIO & a & a & ab & a \\ \cline{2-7}  & Ti 0.60 \({}^{\text{NS}}\) & BIO & a & a & a & a \\ \cline{2-7}  & BI 61.82 *** & COMB & a & b & b & a \\ \cline{2-7}  & TrxTi 0.57 \({}^{\text{NS}}\) & CTR & a & ab & ab & a \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} Transpiration rate \\ \end{tabular} } & Tr 6.94 *** & ABIO & a & a & ab & ab \\ \cline{2-7}  & Ti 0.79 \({}^{\text{NS}}\) & BIO & a & a & a & a \\ \cline{2-7}  & BI 55.73 *** & COMB & a & a & b & b \\ \cline{2-7}  & TrxTi 1.13 \({}^{\text{NS}}\) & CTR & a & a & ab & ab \\ \hline \multirow{4}{*}{
\begin{tabular}{c} iWUE \\ \end{tabular} } & Tr 6.23 *** & ABIO & a & b & a & b \\ \cline{2-7}  & Ti 0.47 \({}^{\text{NS}}\) & BIO & a & b & a & b \\ \cline{2-7}  & BI 136.54 *** & COMB & a & b & a & ab \\ \cline{2-7}  & TrxTi 1.52 \({}^{\text{NS}}\) & CTR & a & a & a & a \\ \hline \hline \end{tabular}  
* \(0.01<p<0.001\); *** \(p<0.001\); NS not significant.  
\end{table} 
Table 2: Results of two-way ANOVA [Treatment (Tr), time (Ti), block (Bl) TrxTi interaction (TrxTi)] on the gas exchanges traits. Abbreviations as in Figure 1. Statistics: F- and \(p\)-values. Within each gas exchanges traits and time of exposure, the different letters indicated statistical differences among the mean of the treatments (\(p<0.05\), test of Tukey).