Impact of Drought, Salinity, and Their Combination on Growth, Mineral Content, and Plant Secondary Metabolites of Tomatoes (Solanum lycopersicum L.).

Drought and salinity are significant challenges to tomato production under climate change. A 2-year experiment (2023-2024) with Solanum lycopersicum cv. Resi evaluated the effects of drought (25%, 12.5%, and 6.25% of soil weight) and salinity (0.5% and 1.0% NaCl), applied individually and in combination, on yield, mineral uptake, and secondary metabolism. Drought reduced yield by 28%, salinity by 17%, and their combination by 27%. Moderate drought and salinity increased potassium (K+) uptake, whereas severe stress reduced calcium (Ca2+) concentration and disrupted overall ionic homeostasis. Lycopene and β-carotene decreased under combined stress, whereas chlorogenic acid and naringenin chalcone increased, indicating enhanced antioxidant metabolism. Antioxidant activities (TEAC, DPPH, and TPC) rose under moderate stress, particularly in the warmer 2024 season. Correlation analysis showed that magnesium (Mg2+) accumulation was positively associated with antioxidants and carotenoids, supporting redox balance under stress conditions. Overall, these findings indicate that tomato adaptation to drought and salinity relies on coordinated ionic regulation and antioxidant adjustments, both influenced by environmental conditions.