Preliminary study on the effect of LED light and cytokinine on the growth of pear plants in vitro

In the past two decades, light emitting diodes (LED) have become an alternative source of light for plant tissue culture, due to their low energy consumption, low heat emission,  specific wavelength irradiation etc. The effect of three LED lights (white, blue and mixed) and two cytokinines (6-benzylaminopurine or meta-Topolin) on the growth of pear (Pyrus communis L. ‘OHF 333’) in vitro was studied. The plantlets were cultivated in microboxes (SacO₂, Belgium) on a modified MS (Murashige and Skoog, 1962) solid medium supplemented with 2.5 µM 6-benzylaminopurine (BAP) or meta-Topolin (mT). The plantlets were grown in controlled room using Philips GreenPower LED research module. Three groups of LEDs emitting in white (W), blue (B), mixed (W:R:B:far-red=1:1:1:1) (BR) lights were applied. Biometric parameters, content of photosynthetic pigments and gas-exchange analysis of the plants were measured after three four weeks passages under corresponding light/cytokinine treatment. The results obtained indicated that different LEDs and cytokinine specifically affected the growth and development of in vitro cultured pear plants. The highest fresh and dry mass distinguished the plants grown under white LED light with both cytokinines studied. The maximum values for plant height was achieved in plants grown under white LED light with BAP and blue LED light with mT.  The leaf sizes of plants grown on mT enriched medium were larger than those grown on BAP enriched medium, regardless of light and the largest were the leaves of plants grown under white LED light. Also, plants grown with mT in the nutrient medium showed more intensive photosynthesis, with the difference between the white and mixed LED light being insignificant.