Pony Express HM® cv tomato seedlings of semi-indeterminate growth, from Yurecuaro, Michoacanwere used. The roots of the seedling were removed from peat moss using tap water. The experimental units consisted of an airtight container with a capacity of 3.5 L⁻¹, and 2.5 L⁻¹ distilled water was added to each container. Each container contained 20 plants, and five replicates were used. Tomato plants were grown for three weeks in modified Hoagland nutrient solution containing 1.2 mM KNO₃, 0.8 mM Ca(NO₃)₂, 0.2 mM KH₂PO₄, 0.2 mM MgSO₄, 50 mM CaCl₂, 12.5 µM H₃BO₃, 1 µM MnSO₄, 1 µM ZnSO₄, 0.5 µM CuSO₄, 0.1 µM (NH₄)₆Mo₇O₂₄, 10 µM Fe-EDTA, and 0.1 µM NiCl [21] [23].

Hoagland solution was supplemented with four concentrations of Ca (25, 50, and 100 mM), and Hoagland solution served as the control. To avoid root hypoxia, oxygen was supplied by a pump (Elite® 802). The roots were pretreated with 10 mM H₂O₂ for 8 hours. Plants were conditioned again in the nutrient solution containing the corresponding treatment for one week. The average CO₂ level in the experiment was 502 ppm. The relative humidity was 37%, and the temperature was 23˚C (WatchDog model A160 temp/HR/CO₂, Spectrum Technologies Inc.).

Data were analyzed using SAS software ver. 9.3. An analysis of variance (Proc ANOVA) was performed. The comparison of means was made using the Tukey test with a significance value of 95% (P ≤ 0.05) in order to determine the significant differences between the variables.

The statistical analysis showed that root length, seedling height, stem diameter, chlorophyll content and fresh root biomass did not present statistically significant differences (P ≤ 0.001) with the NS or with the additions of the levels of Ca (Table 1). There were statistically significant differences in fresh stem and leaf

Means followed by different letters in each column indicate significant differences among treatments (***P ≤ 0.001; **P ≤ 0.01). C.V coefficient of variation.

biomass when 100 mM Ca was added to the SN, the increase was 25% and 38% compared to the control (Table 1). There were no significant statistical differences (P ≤ 0.001) between treatments with the variables dry biomass of leaves, stem and root (Table 1).

In the multi-elemental microanalysis for the leaves, only nine nutrients (macro- and micronutrients) were detected among the treatments (Table 2). Statistical analysis showed that there were no statistically significant differences for C, O, N, P, K, Mg, and S with NS and the different levels of Ca (Table 2). However, it was observed that as the level of Ca (100 mM) in the NS increased, the Ca content in the leaf increased by 34.50% compared to the control treatment (Table 2). There were statistically significant differences (P ≤ 0.001) for Cl, since with the addition of 50 mM Ca in the NS, it increased by 13.15% compared to the control.

The statistical analysis showed that the immersion of roots in peroxide in a period of 8 hours had no effect on the variable root length, stem diameter, chlorophyll content, fresh root biomass and fresh stem biomass (Table 3). There were statistically significant differences in seedling height, with the 25 mM Ca treatment, the increase was 19.75% compared to the control. There were statistically significant differences for the fresh biomass of leaves with 100 mM Ca, the increase was 60.80% compared to the control (Table 3). There were no statistically significant differences for the variables of dry biomass of leaf, stem, and root. A

Means followed by different letters in each column indicate significant differences among treatments (***P ≤ 0.001; **P ≤ 0.01). C.V coefficient of variation.

Means followed by different letters in each column indicate significant differences among treatments (***P ≤ 0.001; **P ≤ 0.01). C.V coefficient of variation.

study by Souri and Dehnavard [24] on 17-week-old tomato plants found that Ca nitrate significantly affected plant height, leaf area, and number of lateral roots compared to urea, and sulfate of ammonium.

When the roots are exposed to peroxide and then restored in nutrient solution, it was shown that those with 25 mM Ca, carbon in leaves increased by 1.46% compared to the control and by 7.33% compared to the treatment with 50 mM Ca (Table 4). There were no statistically significant differences for O and N. The

Means followed by different letters in each column indicate significant differences among treatments (***P ≤ 0.001; **P ≤ 0.01). C.V coefficient of variation.

statistical analysis showed that with 50 mM of Ca in the NS, the concentration of P and K in leaf tissue increased by 44.11% and 29.85% compared to the control (Table 4). The Ca concentration in the leaf increased with the 100 mM Ca treatment by 41.29% compared to the control (Table 4), and higher by 29.35% compared to the Ca concentration in the treatment without peroxide immersion (Table 2). There were no significant differences for Mg and Cl between treatments. The S and Fe in leaf tissue was significantly higher in the control treatment by 56.14% and 8.33% compared to the treatment with 100 mM Ca (Table 4).

The values in tomato roots once exposed to peroxide and its reconditioning to NS are shown in Table 4. The multielemental microanalysis detected 10 nutrients in the root (macro- and micronutrients). The statistical analysis showed that there were no significant statistical differences for C, O, N, P, and S. The root control treatment presented significant statistical differences for K and Cl, as it was higher by 47.61% and 55% with respect to the treatment with 100 mM Ca (Table 4). The statistical analysis showed that with 100 mM of Ca in the NS, the Ca and Mg in the root increased by 83.48% and 40.47% (Table 4).

Although, in the experiment without root immersion to peroxide, it presented statistically significant differences for fresh stem biomass and fresh leaf biomass (2.89 g and 2.31 g) (Table 1). However, the values in the growth parameters and dry weights were lower than the results observed in the experiment with root immersion (Table 3), for example, H₂O₂ induced an increase in root length and seedling height in a 12.01% and 17.36% (Table 3 and Figure 2), with respect to the treatment without immersion (Table 1 and Figure 1). While H₂O₂ had a positive effect on growth, however, when tomato plants are subjected to salinity stress (NaCl), it is accompanied by significant reductions in shoot weight, plant height and number of sheets [25].

Plants uptake and translocate nutrients from the root to the conducting vessels (xylem and phloem) [20]. Nutrients are redistributed to the entire system, and in the case of the tomato, the greatest demand for nutrients is given to developing organs such as leaves, flowers, and fruits [20].

The O and N values did not differ between the experiments with and without H₂O₂ in the leaf tissue (Table 2 and Table 4). For the case of P, K, and Mg (0.75, 2.51, 0.40%) the concentration in foliar tissue was higher (Table 2), with respect to plants with root immersion for the same macronutrients P, K, and Mg (0.68, 2.11, and 0.34%, respectively) (Table 4). H₂O₂ induced the concentration of C, Ca, S, Cl and Fe (51.15%, 4.02%, 0.57%, 0.49% and 0.12%) in the leaves (Table 4) being higher than the same nutrients C, Ca, S and Cl (49.96, 2.84, 0.31 and 0.38%) reported in the experiment without immersion in peroxide (Table 2).

The majority accumulation of nutrients in the root due to the effect of immersion in H₂O₂ were C, O, N, K, Ca, Mg, P, S, Cl, and Fe (50.59%, 43.60%, 3.22%, 2.52%, 2.06%, 0.42%, 0.40%, 0.21%, 0.20%, and 0.13%, respectively). However, in this case K, Ca, Mg, S, Cl, and Fe presented statistically significant differences (Table 4). Bautista et al. [20] performed a multi-element analysis on roots, stem/branches and leaves in cherry tomato plants in fruiting stage. They found that the concentration of mineral nutrients in roots such as C, O, N, P, K, and Ca, were below the values observed in roots with immersion in H₂O₂ (Table 4).

Some nutrients were below the optimal range reported, such as, P, K, and Cl (Table 2). The N, Ca, Mg, and S in leaves without root immersion were within the optimal range reported (Table 2). Nutrient levels in tomato leaves during the five-leaf phenological stage were 3.0% N, 1.0% Ca, 0.3% Mg, and 0.3% S [26]. In the case of seedlings with root immersion in H₂O₂, K was below the optimal range reported (Table 4).

The N, P, Ca, Mg, and S were within the optimal range reported (Table 4), according to the values described by Hochmuth et al. [26]. For their part, Bautista et al. [20] in the multielemental profile in tomato leaves, found in their values that Mg, S, Cl and Fe were higher than the values reported in our experiment with and without the addition of H₂O₂ (Table 2 and Table 4). While C, O, N and P the highest values were in our experiment, possibly due to the phenological stage (seedling). According to Hartz et al. [27] the optimal ranges for the main macronutrients in tomato leaf tissue are 3.89% N, 0.32% P, 2.24% K, 3.04% Ca, 1.25% Mg, and 0.97% S. On the other hand, Campbell [28] reports that the optimal ranges for tomato are 3.5% N, 0.30% P, 3.5% K, 3.0% Ca, 0.35% Mg, and 0.2% S respectively.