How LED light rooting in vitro affected Gerbera acclimatization efficiency

The objective of this study was to evaluate the acclimatization efficiency of Gerbera shoots, in vitro rooted under LED lights. For the experiment, Gerbera jamesonii 'Big Apple' shoots were rooted on a MS medium with 1 µM IAA, 30 g dm^-3 sucrose and 5 g dm^-3 BioAgar, pH 5.7. Three different LED lights were tested (B - blue, R - red, RB - blue and red mixture 70/30) and fluorescent light (Philips TL-D 36W/54) as a control. PPFD was 35 µM m^-2 s^-1. After 6 weeks, all shoots formed adventitious roots and they were prepared for acclimatization. The agar remains were washed off and the plants were immersed in a 0.1% Topsin M 500 SC and planted in containers filled with TS2 substrate (Klasmann-Deilmann). The plantings were covered with a polypropylene transparent film and were kept in a greenhouse at a temperature of 19/22°C. After 10 days, the boxes were gradually uncovered to reduce humidity, while the light intensity was increased. At the end of the acclimatization, biometrical observation and analyses, the dry mass of the leaves and roots, and the stomata features of the acclimatized plants were recorded. After 6-week ex vitro culture, all gerbera plants were 100% acclimatized. The longest shoots had plants rooted under red light, while those rooted under monochromatic blue light had the highest number of leaves and the leaf blades had the largest surface. The control plants showed the lowest number of roots when compared to the plants rooted under all LED combinations. The shortest roots after acclimatization were observed in gerbera rooted under RB, while the highest dry mass was recorded in those rooted under monochromatic light. There were no differences in the stomata frequency in acclimatized plants rooted under different light spectra. Stomata and their pores of plants rooted on RB light were shortest and had the smallest area.