The aim of our study was to evaluate the effect of the change in photoperiod and the plant growth regulators on the characteristics of seedlings for stone cultures under in vitro conditions. Cultivation of the explants was carried out on three variants of nutrient media according to the protocol of Murashige and Skoog: without growth regulators (control), with the addition of 0.5 mg/l of kinetin (Kn), and with the addition of 0.5 mg/L of indole-3-oil acid (IBA). The study was conducted on 6 photoperiod variants (8/16, 12/12, 14/10, 16/8, 20/4, and 24/0 h). VSL-2 microshoots’ growth characteristics (shoot length and root length, number of leaves, number of roots, number of shoots/ejection, percentage of rooting, the total chlorophyll) after 6 weeks of cultivation in the climate chamber Ve-Farm Clima 2 under a lighting intensity of 40 μmol m–2 s–1 and the spectral ratio of red, blue, and green components of the spectrum as 2.5 : 1.0 : 0.4 and a temperature of 25 ± 0.2°C were determined. A variance analysis of the results of the two-factor experiment showed that parameters such as the wet and dry weight, the number of leaves and the length of the shoot were more dependent on the photoperiod with a factor of 56.6‒80.7%. In conditions of long daylight, photoperiodic sensitivity was manifested in an increase in shoot length by 3.1‒4.5 times and the leaf plates’ area by 2 times on MS medium. Although the absence of a dark phase increased the growth characteristics of shoots in vitro by 2 times in variant with IBA, it had a negative effect on the morphology of leaf plates. A photoperiod of 20/4 hours was found to be optimal for the development and rooting of VSL-2 microshoots under in vitro conditions when using a nutrient medium without growth regulators, and in combination with IBA, the maximum rooting percentage was fixed and 11.4 roots per shoot.
Mogilevskaya et al. (Wed,) studied this question.
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