Adaptive Responses of Four Medicinal Plants to High Altitude Oxidative Stresses through the Regulation of Antioxidants and Secondary Metabolites

Abstract

The conservation of medicinal plants, particularly endangered or endemic species, is of the utmost importance, especially in light of inevitable climate change and its consequences. Species inhabiting high altitudes adopt exceptional defense mechanisms in response to abiotic stresses as a survival strategy. The objective of the current study was to investigate the effects of altitudinal variations on secondary metabolite accumulation and antioxidant enzyme capacity in four plants (Cotoneaster orbicularis, Crataegus x sinaica, Echinops spinosissimus subsp. Spinosissimus, and Tanacetum sinaicum) growing naturally on the Sinai Peninsula’s high mountains. Plant leaves and soil samples were collected from three altitudes between 1500 and 2250 m a.s.l. to evaluate the adaptive responses of these species in relation to high-altitude oxidative stresses. The results showed that at higher altitudes, the electrical conductivity and the micronutrient contents of the soil decreased, which may be due to the prevalence of silt and clay decreasing at higher altitudes. Chlorophyll a, chlorophyll b, ascorbic acid, and total soluble protein showed similar results in relation to higher altitudes for all species. On the other hand, proline, total soluble sugars, carotenoids, phenols, tannins, and flavonoids increased in response to high altitudes. The activity levels of catalase and ascorbic acid peroxidase showed a significant increase aligned with higher altitudes, while a significant decrease in activity levels was obtained for polyphenol oxidase. In conclusion, the present findings showed that Cotoneaster orbicularis exhibited the maximum response for coping with high-altitude stresses, followed by the remaining three species regarding the level of biochemical and physiological responses. The present work will help formulate conservation plans for important medicinal species.

Light-Dependent Regulatory Interactions between the Redox System and miRNAs and Their Biochemical and Physiological Effects in Plants

“….− in Arabidopsis [42,43]. Induction of ROS formation by high light intensity is accompanied by the accumulation of various antioxidant compounds, as observed for the increasing level of carotenoids, phenols, tannins, and flavonoids with increasing altitudes and light intensity in shoots of four medicinal plant species grown at natural habitats [44]. Similar results were obtained for carotenoids, phenols, tannins, and flavonoids in shoots of other five species collected at various altitudes [45].…”

“…The enzymatic antioxidants also have an important role in the removal of excess ROS under high light. Under natural conditions, the activity of catalase and APX became greater at higher altitudes (greater light intensity) in four plant species [44]. In addition, the catalase, SOD, and peroxidase activities also increased with increasing altitudes in Leymus secalinus [57].…”