Effect of coherent radiation on the morphometric and functional characteristics of valuable lavender and lavandin regenerants in vitro, ex vitro and in vivo

Lavender (Lavandula sp.) cultivars and hybrids are valuable fragrant plants widely cultivated in countries with an arid climate and used for ornamental gardening, perfume and the pharmaceutical industry. The main cultivated plants in the Crimea are Lavandula angustifolia Mill. and L. angustifolia × L. latifolia Medie. The monitoring of phytopathogens at lavender and lavandin collection plots and industry fields revealed that many of them were damaged by viral diseases. To clean up and obtain qualitative planting material, explants of valuable cultivars ('Belyanka', 'Record', 'Rabat', 'Snezhnyi Bars') were introduced into the in vitro culture on modified B5 and MS media at 24±1°C, 16-h photoperiod with light intensity 37.5 μmol m^-2 s^-1. Samples were collected after 2 and 4 months of culture. From one explant 2-5 adventitious microshoots, 2.3-6.4 cm in height, were regenerated. In order to improve the ways of in vitro multiplication for the unique lavender and lavandin genotypes laser light (computerized laser irradiation system for plant objects LPI-2/C650/60) was used, morphometric indexes were estimated and the functional state of plants was analyzed with the parameters for slow chlorophyll fluorescence induction (with fluorometer LPT-3/CFL). The growth and adaptability of the plant material ex vitro and in vivo were examined. Various irradiation power densities were used: from 2 to 15 mW m^-2 and the time of exposure from 60-480 s. The observations were carried out every 5 days for 30 days after the influence of coherent radiation, and 2 months after the material was transferred to the soil substrate. An increased growth of 30-65%, compared to the control, and the formation of new clustering nodes were noticed at lower power densities 2-4 mW m^-2 and under shorter durations of exposure (60 s). Photoinhibition wasn't observed. The relative indexes of slow fluorescence (F_m-F_st)/F_m were 0.43-0.71 a.u., the viability index (F_m/F_st) 1.12-2.03 a.u. Active rhizogenesis was noted after 15-20 days. The maximum growth increase in vivo was observed in cultivars 'Rabat' and 'Snezhnyi Bars' (height 10.3-14.2 cm, on a single regenerant 6-10 shoots were formed from the axillary buds). The obtained results can be used to accelerate breeding processes and the production of virus-free planting material of lavender and lavandin.