## 4 Discussion
The results of this study showed that the WUE of the tested tomato cultivars was in the range of 33-52 kg m\({}^{-3}\) with respect to the salinity treatments, while an overall WUE value of 36-47 kg m\({}^{-3}\) was obtained with respect to the nutrient treatments. Low-salinity environments ease the uptake of irrigated nutrient solutions, which can enhance the vigor of vegetative parts and tomato fruit yields [16; 17; 18]. In general, salinity stress induces a reduction in the uptake of nutrients, resulting in a low fruit yield. In this study, it was also observed that there was a significant reduction (32.6-39.2%) in total fruit yield in the plants treated with high salinity (i.e., S3) compared with the plants treated with low salinity (S1). This could be due to the reduction in vegetative growth and flower development under high-salinity stress conditions [28; 29]. In the present study, concentrations of Na\({}^{+}\), Ca\({}^{2+}\), and K\({}^{+}\) decreased in leaf tissues with increasing salinity stress, and this led to lower availability of nutrient solution to the plants (Table 5). These results are in line with those reported by [PERSON] and [PERSON] [48], who reported a trend of decreasing concentrations of several minerals, such as Na\({}^{+}\), Ca\({}^{2+}\), and K\({}^{+}\), in tomato leaf tissues with increasing water stress, due to high salinity. In general, salinity stress leads to a decrease not only in nutrient uptake by the plant's root system, but also in nutrient transfer from roots to shoots. This is the result of factors such as limited transpiration rate, decreased active transport, and decreased membrane permeability [24; 25]. When plants are exposed to high salt concentrations, this causes a water deficit in the plants, which is detrimental to growth. As a result of the increased accumulation of Cl\({}^{-}\) and N\({}^{+}\), plants start to experience phytotoxicity and are prevented from absorbing certain nutrients, which leads to nutritional imbalances [8; 9]. These elements have an adverse effect on the physiological and metabolic functions of plants, including cell division, respiration, and photosynthesis [10; 11; 12; 13], all of which lead to a decrease in vegetative growth and crop yield. In previous studies, the decrease in tomato yield under high EC was attributed to smaller fruit weight and lower number [48; 49]. Another problem often seen in tomato grown under high EC is the increased incidence of blossom-end rot (BER) caused by decreased calcium (Ca\({}^{2+}\)) uptake by roots and increased resistance to xylem transport inside the fruit. However, increasing levels Ca\({}^{2+}\) in the nutrient solution reduced the incidence of BER [50]. [PERSON] et al. [49] reported that tomato yields under salinity conditions of 4.6, 8.0, and 12.0 dS m\({}^{-1}\) were lower compared with those under 2.3 dS m\({}^{-1}\). Fruit yields under salinity conditions of 4.6 and 8.0 dS m\({}^{-1}\) were reduced because of fruit weight, whereas under 12.0 dS m\({}^{-1}\), both fruit number and weight were reduced by 5.1% per dS m\({}^{-1}\) above 2 dS m\({}^{-1}\)[51]. The levels of chlorophyll, Ca\({}^{2+}\), and K\({}^{+}\) concentrations in the leaves of the Feisty-Red cultivar were significantly higher compared with the Valouro-RZ cultivar. However, the concentration of Na\({}^{+}\) was higher in Feisty-Red leaves, although it was not significantly different when compared with other cultivars (Table 9). These results are in line with those reported by [PERSON] and [PERSON] [48], who reported significant and insignificant differences between three tested tomato cultivars in terms of K\({}^{+}\) and Na\({}^{+}\) concentrations, respectively. The plants grafted onto Maxifort rootstock showed significantly higher levels of chlorophyll content in their leaves compared with the non-grafted plants. Furthermore, the grafted plants showed lower Ca\({}^{2+}\) and K\({}^{+}\) concentrations in their leaves than the non-grafted plants (Table 5).