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A study of the effect of various light intensity (75, 135, 230, and 382 µmol/(m2 s)) on the morphogenesis of Stevia rebaudiana (Bertoni) Bertoni in vitro was carried out using a unique LED light source Sun Box (wavelength range of 440–660 nm) developed at the Institute of Automation and Control Processes (Far East Branch, Russian Academy of Sciences). The light spectrum of the Sun Box was close to the solar spectrum. Luminescent light with an intensity of 49 µmol/(m2 s) was used as a control. It was shown that the cultivation of plantlets using an LED source with an intensity of 75 and 230 µmol/(m2 s) promoted the development of plantlets with a combination of morphological and mesostructural parameters important for microclonal reproduction and/or adaptation to the ground. Such plantlets accumulated the maximal weight of the aerial parts and roots, which was especially important for their subsequent transfer into open ground conditions. Plantlets cultivated at a given light intensity with a developed root system would pass the adaptation process faster and it, in turn, would reduce the percentage of plant mortality. The use of a composite LED light source with a certain intensity during in vitro cultivation of S. rebaudiana would allow optimization of the growing and propagation of plantlets and would reduce energy costs compared with the use of fluorescent lamps. [ABSTRACT FROM AUTHOR]

The effect of light-emitting diode (LED) lamps with five different spectra on L. sativa plants (variety Aficion) grown in protected soil conditions was studied. Warm white light (WW) was used as the control (the ratio of blue, green, and red portions in the spectrum was 14 : 48 : 38%). The maximum values of the leaf size and the fresh weight of the aerial parts were found in the RGB group (blue–green–red ratio 32 : 19 : 49%), and the highest values of the dry weight and ash content were in the FS group (blue–green–red ratio 27 : 11 : 62%). The stomatal size and density on the abaxial side of the leaf was the highest in SB plants (blue–green–red ratio 33 : 41 : 38%). This was the most effective combination of parameters in terms of leaf architectonics. An increase in the portion of red light in the spectrum with a decrease in the portion of green light had a positive effect on the development of L. sativa plants, while an increase in the portion of green light in the spectrum positively affected the formation of the stomatal apparatus. [ABSTRACT FROM AUTHOR]

The development of tomato plants (Solanum lycopersicum L., variety Bonsai) under illumination with various LED lamps was studied. Four illumination options—warm white (WW) as control, solar box (SB), red–green–blue (RGB), and red–blue (FS)—were used in the experiment. They were characterized by different combinations of blue (B), green (G), and red (R) proportions in the spectrum: 14% B : 48% G : 38% R (WW), 26% B : 41% G : 33% R (SB), 32% B : 19% G : 49% R (RGB), 27% B : 11% G : 62% R (FS). The photon flux density was 150 μmol quanta/(m 2 s). It was found that the difference in the R : G : B ratio in the spectra did not affect the accumulation of raw and dry mass of the aboveground parts and roots and the water and dry matter content in the green parts of plants. However, significant differences in the structure of the stomatal apparatus were found depending on the ratio of the main wavelengths (R : G : B) in the spectrum. The density of stomata distribution on the underside of the leaf was the highest in plants under WW conditions and the lowest in plants under FS conditions; the spectral composition of the latter was characterized by a decrease in the proportion of green illumination by 4 times and an increase in the proportions of red and blue illumination by almost two times. As expected, the size of stomatal guard cells was the largest in plants under FS conditions and the smallest in plants under WW conditions. The values for plants grown under RGB and SB were intermediate between minimum (WW) and maximum (FS) values. The response of plants to an increase or decrease in the proportions of the main wavelengths (R : G : B) in the spectrum in the range of 20–30% was flexible and did not affect changes in habitus but promoted acclimation to uncomfortable conditions through physiological parameters. It is concluded that a large proportion of green in the spectrum can have a certain effect on the accumulation of water and dry matter in the aboveground parts of plants and the structure of the stomatal apparatus. [ABSTRACT FROM AUTHOR]

The effect of light emitting diode (LED) light sources with different spectra on Eruca sativa Mill., cv. Dikovina plant development was investigated. Experiments were conducted with four types of LED lamps of our own assembly: solar box (SB), red-green-blue (RGB), red-blue (FS), and warm white (WW) used as a control with an energy ratio in the blue-green-red range of 14% : 48% : 38%. Spectra of SB (26% : 41% : 33%), RGB (32% : 19% : 49%), and FS (27% : 11% : 62%) lamps were used to obtain nine different types of lighting ensuring modification of spectra in the course of growing. The plants exposed to FS-RGB, SB-FS, and RGB-SB light sources were characterized with the greatest values of the shoot fresh weight. Transfer of plants to SB resulted in a decrease in development of the plants root system. Transformation of leaf mesostructure after transfer to SB showed that light conditions therein promoted the formation of leaf structure with lower membrane indexes and deformed mesophyll cells. At the same time, cultivation of plants for 2 weeks in SB with subsequent transfer to FS for 4 more weeks stimulated development of internal assimilatory surface of the leaf with the greatest integral indexes of the outer membrane surface of leaf cells (Ames/A) and chloroplasts (Achl/A) as compared with other treatments. As a result, SB-FS plants produced maximal dry shoots and roots biomass. Without alteration of the lighting pattern, plants from box FS were inferior to control plants (module WW) in parameters of leaf mesostructure and ranked second among other types of treatment. The greatest accumulation of P and Ca was observed in FS-RGB where a maximal percentage of shoots and roots dry matter and the greatest concentration of ascorbic acid were found. Transfer of plants from other boxes to FS caused a decrease in accumulation of macroelements in E. sativa plants. Thus, the dynamic lighting applied for growing of E. sativa plants affected their characteristics and could be used for optimization of plant cultivation. [ABSTRACT FROM AUTHOR]

Mesostructure of the photosynthetic apparatus was investigated in the wild plants of ginseng ( Panax ginseng C.A. Mey, Araliaceae) taken from various habitats. The revealed features of the structure of phototrophic tissues (large cells, small number of photosynthesizing cells and chloroplasts per leaf area unit, low values of membrane indices of the cells and chloroplasts) point to stress-tolerant type of ecological strategy ginseng pursues in Nature. [ABSTRACT FROM AUTHOR]