Physiological responses and antioxidant properties of Citrus reticulata under different abiotic stresses mitigated by endogenous melatonin

Abstract

A major commercial fruit in Pakistan, citrus plays an important role in the economy of the country. The current study examined antioxidant responses in citrus plants exposed to various abiotic stresses like industrial pollution, dust pollution, water logging, drought, and salinity, varying in soil properties and agro-climatic conditions, citrus species and cultivars are most susceptible to abiotic stresses in most citrus-producing countries. The effects of abiotic stresses on citrus plants and fruit physiology were studied in six different sites like Thal desert and pollution stressed areas of Faisalabad. A study of the physiological characteristics of various plants has revealed that citrus plants contain more chlorophyll as the concentration of melatonin increases. Integrative elemental and metabolic techniques have been used to study the potential role of melatonin in citrus defense against abiotic stress and to understand the interactions between melatonin and stress-related phytohormones at the elemental and metabolic levels. Citrus plants sensed abiotic stresses based on morphological observations and physiological analysis. Morphological analysis shows that the abiotic stresses adversely affected the leaves, stems and roots. Physiological analysis shows that antioxidant and micronutrients concentrations (boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), chlorine (Cl)) were also adversely effected in citrus plants. Iron concentration was also found higher in healthy plants with a slight difference. Results show that the activity of antioxidants was increased in stressed plants but the activity of melatonin was slightly changed in healthy plants.