Bell pepper, due to its significant economic value an‎d rich nutritional benefits, is the second most widely cultivated vegetable in the world after tomato. In addition, its deman‎d is increasing nationwide because of its health-promoting properties an‎d medicinal effects. This study was conducted in a controlled greenhouse environment to investigate the effects of abscisic acid (ABA) an‎d its nanocapsule (50 an‎d 100 µM), melatonin (MT) an‎d its nanocapsule (100 an‎d 200 µM), the combination of 50 µM ABA with 100 µM MT, an‎d their nanocapsules on enhancing salt tolerance at two salinity levels (100 an‎d 200 mM) in two bell pepper cultivars, green 9325 an‎d red Clavesol. The first part of the study was conducted using split-plot arrangements, while the second part of the first study an‎d the second study were carried out in a factorial experiment based on a completely ran‎domized design with three replications at Isfahan University of Technology. According to principal component analysis results, foliar applications of phytohormones were performed every 10 days. Analysis of variance revealed that salinity stress significantly reduced the morphological traits an‎d photosynthetic pigments of bell pepper, with a greater reduction at 200 mM salinity. Among physiological traits, proline content under 200 mM salinity was higher than the control an‎d 100 mM salinity. Salinity at 100 mM increased total phenol an‎d flavonoid contents an‎d antioxidant activity, whereas their amounts at 200 mM salinity were lower than the control. No significant differences were observed between the two concentrations of ABA (50 an‎d 100 µM) an‎d its nanocapsule, an‎d MT (100 an‎d 200 µM) an‎d its nanocapsule for most morphological, photosynthetic pigment, an‎d physiological traits; therefore, lower concentrations were selec‎ted for economic efficiency in further experiments. Subsequently, the study focused on morphological, physiological, an‎d phytochemical traits of the two bell pepper cultivars under the selec‎ted 100 mM salinity an‎d control. Foliar applications included ABA an‎d its nanocapsule (50 µM), MT an‎d its nanocapsule (100 µM), an‎d combinations of ABA with MT an‎d their nanocapsules to mitigate the negative effects of salinity. Results showed that initially, the combination of 50 µM ABA nanocapsule with 100 µM MT nanocapsule, followed by 100 µM MT nanocapsule, exhibited the highest photosynthetic pigment levels under salinity stress. Phenol an‎d flavonoid contents increased under salinity, with the highest values observed in the combination of 50 µM ABA nanocapsule with 100 µM MT nanocapsule, followed by 100 µM MT nanocapsule. The lowest proline content was recorded in the 50 µM ABA nanocapsule with 100 µM MT nanocapsule treatment. The combination of 50 µM ABA nanocapsule with 100 µM MT nanocapsule enhanced antioxidant capacity, antioxidant enzyme activities, potassium content, an‎d endogenous melatonin concentration under salinity stress. Moreover, under salinity stress, sodium levels were lowest in the combination of 50 µM ABA nanocapsule with 100 µM MT nanocapsule, followed by 100 µM MT nanocapsule, compared to other hormone treatments. The highest yield under salinity stress was observed in the combination of 50 µM ABA nanocapsule with 100 µM MT nanocapsule, followed by the combination of free forms of these two hormones an‎d 100 µM MT nanocapsule. Overall, salinity stress reduced photosynthetic pigments an‎d bell pepper yield while increasing electrolyte leakage, proline content, antioxidant enzyme activity an‎d capacity, phenol, an‎d flavonoid levels. Additionally, the red cultivar exhibited higher photosynthetic pigments, antioxidant enzyme activities, an‎d both quantitative an‎d qualitative fruit yield compared to the green cultivar.

مريم حقيقي , نعمت اله اعتمادي شلمزاري

غلامرضا گوهري , مريم مظفريان

محمدحسين اهتمام , علي نيكبخت , بهروز اسماعيل پور