Abstract
The influence of climatic factors, e.g., low temperature, on the phytochemical composition and bioactivity of the arctic plant Dracocephalum palmatum Steph. ax Willd. (palmate dragonhead), a traditional food and medical herb of Northern Siberia, was investigated. D. palmatum seedlings were grown in a greenhouse experiment at normal (20 °C, NT) and low (1 °C, LT) temperature levels and five groups of components that were lipophilic and hydrophilic in nature were characterized. The analyses indicated that D. palmatum under NT demonstrates high content of photosynthetic pigments, specific fatty acid (FA) profile with domination of saturated FA (53.3%) and the essential oil with trans-pinocamphone as a main component (37.9%). Phenolic compounds were identified using a combination of high performance liquid chromatography with diode array detection and electrospray ionization mass-spectrometric detection (HPLC-DAD-ESI-MS) techniques, as well as free carbohydrates and water soluble polysaccharides. For the first time, it was established that the cold acclimation of D. palmatum seedlings resulted in various changes in physiological and biochemical parameters such as membrane permeability, photosynthetic potential, membrane fluidity, leaf surface secretory function, reactive oxygen species–antioxidant balance, osmoregulator content and cell wall polymers. In brief, results showed that the adaptive strategy of D. palmatum under LT was realized on the accumulation of membrane or surface components with more fluid properties (unsaturated FA and essential oils), antioxidants (phenolic compounds and enzymes), osmoprotectants (free sugars) and cell wall components (polysaccharides). In addition, the occurrence of unusual flavonoids including two new isomeric malonyl esters of eriodictyol-7-O-glucoside was found in LT samples. Data thus obtained allow improving our understanding of ecophysiological mechanisms of cold adaptation of arctic plants.
Highlights
Environmental stress is one of the most important factors limiting the productivity of the majority of economically important crops [1]
Seedlings were cultivated in growth chambers with photoperiod of 16 h light/8 h dark installed under normal temperature conditions (20 ◦C; NT) for two months
The present study demonstrated that long-term cultivation (20 days) of D. palmatum seedlings at low temperature (1 ◦C) damaged plant organ integrity that affected on the rising level of electrolyte leakage and reactive oxygen species misbalance resulting in increasing concentration of malondialdehyde and antioxidant enzyme
Summary
Environmental stress is one of the most important factors limiting the productivity of the majority of economically important crops [1]. Extreme growth conditions can damage the plant habitat, their inner ultrastructure and biochemical composition, causing dramatic changes incompatible with the functions of living organisms [2]. To elevate their vitality, plants have developed the remarkable ability to adapt to severe environmental conditions. Plants have developed the remarkable ability to adapt to severe environmental conditions These specific potentials have allowed the use of plants as crops even in areas with extremely uncomfortable climate conditions [3]. To understand agronomical events in regions with similar weather conditions, it is necessary to use specific cultures that are resistant to the effects of extreme abiotic factors, including temperature. Increased resistance to the effects of chilling temperatures and short-term frosts characterizes this plant species, and it can be defined as a cold-tolerant plant [6]
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