Biochemical Strategy of Drought Resistance of Dry Habitat Plants of Georgia
Abstract
The climatic cataclysms taking place indifferent corners of the world are clear confirmation of the climate negative change in our planet. Especially disturbing is the temperature rise, accompanied by hot waves, forest fires, intensive melting of the ice cover, and other undesirable aftereffects. Under these conditions chances of dying of many plant species significantly increases. Drought resistant plants have the highest potential of adaptation to increased temperature and water deficiency. Thus, knowledge of their biology will be especially important in deserted regions restoration. The nonspecific mechanisms of resistance, especially antioxidant system, are concerned as one of the leading in plants drought resistance. The presented study aimed the comparative study of the indices of antioxidant system of drought resistant species-Astragalus microcephalus Willd. (Astracantha microcephala (Willd.) Podlech) - goat’sthorn, Theucrium polium L. – felty germander, Euphorbia seguieriana Neck. - spurge, Capparis spinosa L. – caper bush, Paliurus spina-christi Mill. – Christ’sthorn, growing indifferent arid habitats of the East Georgia (Iagludja and Kvernaqi hills). The defence mechanisms of the antioxidant system appeared to be partially different in one and the same species of various habitats, as well as indifferent species of the same habitats. Activation of phenolic substances and anthocyanins synthesis against extreme conditions of both habitats (water deficiency, high temperature and intensive irradiation) was common for all tested species. Additionally, activation of peroxidase in Kvernaqi species and intensive accumulation of soluble carbohydrates in Iagludja plants was mentioned.
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Introduction
The latest scientific documentations demonstrating evident negative changes allover the world has been presented in the preliminary report of the world meteorological organization on the climate global situation in 2021. Especially disturbing is the temperature rise, accompanied by hot waves, forest fires, intensive melting of the ice cover, and other undesirable aftereffects. According to data last seven years were regarded as the hottest through the whole history of climate observation (WHO report, 2021).
Climate warming significantly rises the risk of plants dying off under the increased stresses (Allen et al., 2015; Overpeck and Udall, 2010; McDowell et al., 2008). Presumably the area of distribution of many plant species will change. The migration rate will depend on species features, competition, climate conditions, etc. (Garamvolgyi and Hufnagel, 2013) Drought resistant species will have the highest potential of adaptation to increased temperatures and accompanying water deficiency. Thus, the knowledge of their biology will be very important in the restoration of deserted areas; moreover, most of them are used in medicine Drought resistant plants possess evolutionary developed physiological and biochemical mechanisms of stability against water deficiency and high temperature. The nonspecific mechanisms of resistance are regarded as one of the principle under stress conditions; the antioxidant system is of special importance among them (Li, and Liu, 2016; Laxa et al., 2019). Characteristics of the antioxidant system of drought resistant plants of the arid territories of Georgia are practically unexplored.
The presented work aimed comparative studying of some characteristics of drought resistant species growing at different arid habitats of east Georgia (Yagludja and Kvernaqi hills). The study may be regarded as the continuation of previous year’sinvestigations (Badridze et al., 2021).
Content of ascorbic acid, tocopherol, carotenoids, anthocyanins, soluble phenols, proline, total proteins and soluble carbohydrates, as well as the activity of catalase, peroxidase, nitrate reductase and the total antioxidant activity in percents of inhibition have been studied in leaves of experimental plants,
Conclusion
1. Inspite of similarity of climatic conditions of Kvernaqi and Iagludja hills, obtained results let assume that Iagludja conditions are more extreme for plants; which may be linked with soil conditions as well.
2. The antioxidant defence mechanisms of experimental species appeared to be partly diverse following habitats.
3. It is evident that stress-adaptive mechanisms have specific peculiarities; athough these mechanisms are determined by those factors which plant has to adapt.
4. Activation of the phenol-anthocyanin antioxidant defense mechanism against the stress conditions of both studied habitats was common in all tested plants.
5. Together with the phenol-anthocyanin mechanism of stress-protection, activation of peroxidase was expressed in all tested species of Kvernaqi hill; while in Iagludja accumulation of soluble carbohydrates was evident.
