PEG-induced osmotic stress in Mentha x piperita L.: Structural features and metabolic responses

Abstract

The present study investigated whether osmotic stress induced by the exposure of peppermint (Mentha x piperita L.) to moderate and severe stress for short periods of time changes the plant's physiological parameters, leaf anatomy and ultrastructure and essential oil. Plants were exposed to two levels of polyethyleneglycol (50 g L(-1) and 100 g L(-1) of PEG) in a hydroponic experiment. The plants exposed to 50 g L(-1) maintained metabolic functions similar to those of the control group (0 g L(-1)) without changes in gas exchange or structural characteristics. The increase in antioxidant enzyme activity reduced the presence of free radicals and protected membranes, including chloroplasts and mitochondria. In contrast, the osmotic stress caused by 100 g L(-1) of PEG inhibited leaf gas exchange, reduced the essential oil content and changed the oil composition, including a decrease in menthone and an increase in menthofuran. These plants also showed an increase in peroxidase activity, but this increase was not sufficient to decrease the lipid peroxidation level responsible for damaging the membranes of organelles. Morphological changes were correlated with the evaluated physiological features: plants exposed to 100 g L(-1) of PEG showed areas with collapsed cells, increases in mesophyll thickness and the area of the intercellular space, cuticle shrinkage, morphological changes in plastids, and lysis of mitochondria. In summary, our results revealed that PEG-induced osmotic stress in M. x piperita depends on the intensity level of the osmotic stress applied; severe osmotic stress changed the structural characteristics, caused damage at the cellular level, and reduced the essential oil content and quality.

Morpho-Physiological Responses of Alamo Switchgrass During Germination and Early Seedling Stage Under Salinity or Water Stress Conditions

“…Structural changes in the first leaf were similar under both stress situations and they mainly affected the thickness of the mesophyll and the cuticles. The increase in mesophyll thickness match the findings in Mentha x piperita plants treated with PEG 100 g.L -1 [57] and in most plants [58] under salinity stress but is opposite to observations made in Cynodon dactylon [42]. At the epidermal level, both stresses increased the thickness of the cuticle, which is an effective mechanism against water loss under stress [59].…”

Calcium and Calmodulin Are Involved in Nitric Oxide-Induced Adventitious Rooting of Cucumber under Simulated Osmotic Stress

“…It has been reported that osmotic stress significantly reduced the fresh weight and water content in leaf blade and leaf petiole of sugar beet ( Beta vulgaris L.) ( Wu et al, 2016 ). Osmotic stress interfered with various metabolic processes ( Búfalo et al, 2016 ) in plants such as photosynthesis ( Bündig et al, 2016 ) and respiration ( Zorrilla-Fontanesi et al, 2016 ). Previous study has shown that Ca 2+ and CDPK could be involved in adventitious rooting, which was induced by NO in cucumber ( Lanteri et al, 2006 ).…”

Chemical Composition andIn VitroAntioxidant, Cytotoxic, Antimicrobial, and Larvicidal Activities of the Essential Oil ofMentha piperitaL. (Lamiaceae)

“…In the preliminary phytochemical analysis of the essential oil, there was the presence of the main constituents: the majority were menthol, menthone, and menthofuran compounds which were responsible for pleasant odor [8–11]. …”