Effect of different led spectrum regimens on growth and development of Betula pubescens Ehrh. and Rubus idaeus L. in culture in vitro

Light-emitting diodes (LEDs) have shown high efficiency in growing plants both in vivo in greenhouses and in vitro, including clonal micropropagation. The purpose of this study was to analyze the effect of the spectral composition of LED irradiators with different proportions of red (RL) and blue (BL) light on the morphogenesis of microplants of the remontant form of common raspberry (Rubus idaeus L.) cv. Hercules and the selection valuable cultivar of downy birch (Betula pubescens Ehrh.), which is the object of a unified genetic breeding complex (UGBC), previously selected on the basis of drought resistance. In the variant 1, the RL/BL ratio was 80/20%, in the variant 2 it was 70/30%, in the control it was 50/50%. The LED in variant 1 contributed to the greatest increase in morphometric and anatomical characteristics in raspberry microplants, increasing the height of shoots, the number of leaves, stomata density, the height of the leaf epidermis and mesophyll. At the same time, an increase in the proportion of RL/BL led to an increase in the leaf area, leaf surface, and stomatal density in birch microclones; however, the anatomical characteristics of the leaf indicate a decrease in the height of epidermal cells and the size of mesophyll cells. Thus, the LED of option 1 can be recommended for use in clonal micropropagation of raspberries in greenhouses, to optimize growth processes and obtain healthy, normally formed plants, while birch requires additional selection of optimal spectral illumination conditions.