No abstract

This paper presents the comparative anatomical and morphological characteristics of plants of two subgenera: Haworthia and Hexangularis. The study revealed two different strategies of adaptation to arid conditions of the growth of different subgenera of the genus Haworthia. Plants of the subgenus Haworthia adapted to arid conditions by increasing the accumulation of water, the presence of "windows", a smaller stoma size, and a thinner outer wall of the epidermis cells. On the other hand, plants of the subgenus Hexangularis adapted to arid conditions by reducing overheating and transpiration as well as by the presence of papillae and a thickened outer wall of the epidermis cells.

An increase in environmental temperature is one of the most common stress factors for plant organisms. The study of the plants’ adaptation to stress factors remains extremely important and relevant. This article presents the results of a acute short-term influence of hyperthermia on species of two subgenera of the genus Haworthia Duval. We investigated the different levels of antioxidant protection and damage degree of the members of two subgenera of the genus Haworthia at the biochemical level, measuring the lipid peroxidation, superoxide dismutase and peroxidase activities, total flavonoid content and content of photosynthetic pigments with a spectrophotometer. To determine the drought tolerance of plants, the water supply of tissues, water shortage and loss of water after an hour of wilting were measured. The values for different groups were compared by ANOVA followed by the Tukey multiple comparison test. The studied plants were warmed in a thermostat at temperatures of 40 °C and 50 °C for three hours under the conditions of natural light. The control group of plants was kept at 25 °C. The research has shown that H. attenuata, H. limifolia and H. cymbiformis are characterized with the increase of concentration of malonic dialdehyde at 40 °C and 50 °C, but a significant difference of values wasn’t received,which indicates the relative resistance of these plants to the influence of high temperatures. The sharp increase of temperature causes the highest level of lipid peroxidation in H. parksiana plants, along with which, warming to 50 °C launches a mechanism of activation and synthesis of superoxide dismutase and flavonoids for the plants. The studied species of the subgenus Haworthia have a photosynthetic system relatively resistant to thermal stress in comparison to the subgenus Hexangulares. H. limifolia plants have a slight inhibition of photosynthesis. The adaptation of H. cymbiformis to thermal stress is due to the strategy of accumulation of a pool of active enzymes, superoxide dismutase, peroxidase, flavonoids under normal conditions and the activation of new peroxidase enzymes as a result of stress. H. attenuata is characterized by activation of new enzymes of superoxide dismutase and peroxidase under stress. It was found that H. cymbiformis and H. attenuata are more heat resistant in comparison with the other two species. Acute short-term hyperthermia has a different influence on the antioxidant system of different species of Haworthia. H. limifolia has the highest drought tolerance, H. cymbiformis has the lowest, the other two species from different subgenera have similar drought tolerance indicators. We did not find any dependence of the mechanisms of action of the antioxidant system under hyperthermia on the type of adaptation to arid conditions at the anatomical level in plants of different subgenera of the genus Haworthia.

New technologies of reintroduction of plant species presuppose implementing both traditional and biotechnological methods for obtaining certain planting materials. However, plants cultivated in vitro exist in specific conditions that lead to changes in their structural and functional state. This explains why it is hard for them to adapt to ex vitro and in situ conditions. Therefore, there is a need for the development of a multistage method of cultivating in vitro plants that would make the influence on their adaptive mechanism in ex vitro and in situ conditions possible. One of its stages is the optimization of the light regime of cultivation which can both initiate the change of the state of the photosynthetic apparatus of plants and increase their bioproductivity stimulating the work of their protective system. This work studies changes in the morphogenesis, growth data and pigment composition of the rare species of Gentiana lutea L. of three populations in the Ukrainian Carpathian (mountains Pozhyzhevska and Sheshul-Pavlyk, plateau Lemska) in vitro focusing particularly on the cultivation light regime. The research has proved the inefficiency of using fluorescent lamps of daylight lamps (LD) type as source of illumination because the low intensity of luminous flux in the area of photosynthetically active radiation (PAR), as well as high proportion of wavelength of blue (400–500 nm) and green (500–600 nm) range in the spectrum cause specific reactions of photomorphogenesis, which, despite the high content of pigments in plastids, lead to poor development of root systems, stretching the stems, formation of small leaves with thin leaflet plate, generally low productivity and low adaptive potential of G. lutea plants to ex vitro and in situ conditions. Complement of cold white light lamps to the fluorescent lamps LD type in the ratio of 1 : 1 enables one to increase the intensity of illumination in the field of PAR and raise the fraction of wavelength of red range (600–700 nm). Such light conditions both improve the bio-productivity of G. lutea plants of all three populations cultured in vitro in comparison to the LD type regimen, reducing the content of chlorophyll b and carotenoids in light-harvesting complexes of photosystems and facilitate an increase in the microclonal multiplication factor without using higher concentrations of exogenous growth regulators,which significantly reduces the cost of the process of obtaining planting materials. It was proved that a combination of LD type lamps, cold white light lamps and phytolamps in the ratio 1 : 1 : 0.6 should be used on the final stages of preparation of the planting material of G. lutea before transferring it to ex vitro and in situ conditions. This relates to the fact that the increase of the wavelength of the red range results in the widening of the active surface of the leaves, rise in the content of photosynthetic pigments, and the noticeable growth of the aboveground and underground parts of the plants. The article assumes that the use of such illumination mode will ensure a faster transition of cultured in vitro G. lutea plants from heterotrophic to autotrophic nutrition, improving their adaptive potential and enabling easier adaptation to non-sterile ex vitro and in situ conditions.

Peppermint grass, as a raw medicinal plant material, has great importance for the pharmaceutical industry. The influence of clonal micropropagation and chemotherapy has been established in vitro on six breeds of Ukrainian selection peppermint plants, in particular on the sprouts’ conductive system structure and tissue development, general biomass accumulation, and in vivo productivity of breeds. The influence of clonal micropropagation and chemotherapy on important productivity indices of the plants has been established in vitro in six breeds of Ukrainian selection peppermint plants as pharmacopeial plants. The linear meter method, the microscopic method, the standard histochemical methods, and the statistical analysis method were used in the studies. A clear tendency to increase in the leaf cover, air-dry leafage and rhizome was observed in breeds of Ukrainian selection peppermint to which propagation and in vitro improvement technology was applied. The air-dry leafage yield significantly increased after in vitro culture from 7.6% in the Lidiia breed to 51.4% in the Chornolysta breed recognized as a state mint standard in Ukraine. The leaf cover increased from 8% to 21% in peppermint plants improved in іn vitro culture. This method promoted essential oil quantity increase from 9.8 to 28.6 kg per hectare. The rhizome yield increased by 6.3–40.4% in all peppermint plants breeds after improvement in in vitro culture on average within one vegetation year. The Lebedyna Pisnіa and Mama breeds were characterised by the most intensive development of all investigated anatomic and morphological indices after in vitro culture: rhizomes yield increased by 40.4% and 40.1%, air-dry leafage by 37.1% and 26.6%, leaf cover by 21.0% and 13.0%, and essential oil quantity per hectare increased by 38.1% and 28.5% accordingly. Anatomical and histochemical studies of sprouts of Ukrainian selection peppermint plants breeds confirmed increase in xylogenesis intensity in the majority of the studied breeds (except Lidiia and Ukrains’ka Pertseva) after in vitro culture improvement. The xylogenesis process was most expressed in the Mama and Chornolysta breeds. Air-dry leafage, rhizome yield, and leaf cover increased in all peppermint plants breeds after in vitro improvement, which could be critical for the pharmaceutical industry.