Changes in Ecophysiology, Osmolytes, and Secondary Metabolites of the Medicinal Plants of Mentha piperita and Catharanthus roseus Subjected to Drought and Heat Stress

Abstract

Global warming contributes to higher temperatures and reduces rainfall for most areas worldwide. The concurrent incidence of extreme temperature and water shortage lead to temperature stress damage in plants. Seeking to imitate a more natural field situation and to figure out responses of specific stresses with regard to their combination, we investigated physiological, biochemical, and metabolomic variations following drought and heat stress imposition (alone and combined) and recovery, using Mentha piperita and Catharanthus roseus plants. Plants were exposed to drought and/or heat stress (35 °C) for seven and fourteen days. Plant height and weight (both fresh and dry weight) were significantly decreased by stress, and the effects more pronounced with a combined heat and drought treatment. Drought and/or heat stress triggered the accumulation of osmolytes (proline, sugars, glycine betaine, and sugar alcohols including inositol and mannitol), with maximum accumulation in response to the combined stress. Total phenol, flavonoid, and saponin contents decreased in response to drought and/or heat stress at seven and fourteen days; however, levels of other secondary metabolites, including tannins, terpenoids, and alkaloids, increased under stress in both plants, with maximal accumulation under the combined heat/drought stress. Extracts from leaves of both species significantly inhibited the growth of pathogenic fungi and bacteria, as well as two human cancer cell lines. Drought and heat stress significantly reduced the antimicrobial and anticancer activities of plants. The increased accumulation of secondary metabolites observed in response to drought and/or heat stress suggests that imposition of abiotic stress may be a strategy for increasing the content of the therapeutic secondary metabolites associated with these plants.

PEG 6000-Stimulated Drought Stress Improves the Attributes of In Vitro Growth, Steviol Glycosides Production, and Antioxidant Activities in Stevia rebaudiana Bertoni

“…ROS are signalling moieties that play a significant role in the controlled response against stress and programmed cell death. The defensive response is created under appropriate concentration of stress elicitor whereas concentration above threshold causes death of cells [26][27][28].…”

Melatonin Counteracts Drought Induced Oxidative Damage and Stimulates Growth, Productivity and Fruit Quality Properties of Tomato Plants

“…These steps are essential to modulate a wide array of plant responses. These influences include the development of enzymatic and non-enzymatic antioxidative systems, alteration of endogenous phytohormones, accumulation of osmolytes and expression of specific stress-related genes [ 17 , 18 , 19 , 20 ].…”

Regulation of Agronomic Traits, Nutrient Uptake, Osmolytes and Antioxidants of Maize as Influenced by Exogenous Potassium Silicate under Deficit Irrigation and Semiarid Conditions

“…Currently, water scarcity is predicted to become the most severe environmental challenge that affects the agricultural sector and multiple socio-economic activities in many regions worldwide, especially with frequent climatic changes [3]. The harmful effects of drought stress on plants are usually associated with several events at cellular, biochemical, physiological and molecular levels that may enable the plants to adapt or tolerate such conditions [4][5][6]. These responses include the rapid generation of reactive oxygen species (ROS) [7], development of an array of complex antioxidant (nonenzymatic and enzymatic) systems [8], regulation of the expression of tolerance related genes [9] and alternation of nutrient uptake [10].…”