## 4 Discussion  
The three pomegranate cvs. that we used in the present work differ in saline tolerance and provided a support for the study of the physiology and biochemistry of salt tolerance in pomegranates, avoiding the problem of comparisons between genetically unrelated cultivars. Salt stress usually affects the plant growth, development, and antioxidant capacity as well. This decrease in plant growth may occur due to excess accumulation of salts around the root zone, which affects the water uptake. Water plays an important role in the physiology of plants, and maintaining higher leaf water content is a physiological mechanism of enhancing salt stress tolerance. Water potential is a basic parameter that is commonly used to determine the tolerance for salinity stress. Our results showed that tolerant cvs. (Ermioni and Wonderful) had a lower reduction in \(\Psi\) compared with the sensitive cv. (Grenada) under salt stress. A similar decrease in \(\Psi\) under stress conditions was reported by many earlier researchers in other plants [24]. Salinity significantly reduced the carbohydrate concentration in all cvs. for all salts. The concentration of carbohydrates in the leaves was affected by salt treatments, suggesting that the salt affected some sugar-related metabolism in the leaves. Previous reports showed that exposure to abiotic stresses such as heavy metals [15] influenced the sugar metabolism. Our results agree with the findings of [3; 25], who observed a similar decrease in the carbohydrate concentration due to salinity in pomegranate plants. Furthermore, many authors [26] described related results in pomegranate plants. The porphyrin concentration was reduced at the highest KCl and K2 SO4 concentrations, and Grenada was the most susceptible among the three cvs. The decrease in porphyrin concentration could be ascribed to the decrease in Fe absorption, which is a basic component of the porphyrin molecule due to its competition with the K ion of salts (KC and, K2 SO4) and salt toxicity. Our findings are not in agreement with those of [27], that the Profeta Partanna pomegranate cv. did not show any differences in phenols and ellagic acid concentrations due to salinity. In addition, [28] reported similar results observing the salinity-activated biosynthesis of phenols in leaves. However, the close relationship between antioxidants and resistance to salinity in various plant species has been previously reported for peas [29], cotton [30], and rice [31]. The ability of plants to inactivate ROS mainly depends on the antioxidant defense system, including nonenzymatic components [32]. The nonenzymatic components of the antioxidant defense system consist of various secondary metabolites, such as hydrophilic phenols and flavonoids, organic acids, lipophilic carotenoids, and water-soluble ascorbate. The existence of phenol metabolism is considered as one of the responses to abiotic stress [16; 33]. Plant antioxidants are a source of bioactive compounds. They play an important role in plant functioning and mitigate the adverse effects of abiotic stresses, but they are also beneficial for human health [34]. Phenols are considered one of the most well-known antioxidants, and their increase in plant tissues under salinity probably explains their involvement in plant protection against oxidative damage due to salt stress [35; 36]. Many authors [37] have reported that salinity causes disorders to plant metabolism, leading to the increased biosynthesis of phenols. The phenol structure is aromatic rings and free hydroxyls that can detoxy free radicals (ROS) [38; 39]. In our experiment, the increase in phenol concentration was ascribed to antioxidant mechanisms in response to oxidative stress caused by salinity. However, the ROS produced by salinity were inactivated by various antioxidants from the photosynthetic electron transport chain within chloroplasts [40] and helped to detoxy ROS (S) [41; 42].