Effect of LED lighting on the growth of micropropagated pear plantlets (Pyrus communis L. OHF 333)

Light by their characteristics - the intensity, quality, and duration - is on the most important factors for plants. The light source used in plant tissue culture is fluorescence lamp (FL). But in recent years, 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 LED light on the growth of micropropagated pear plantlets (Pyrus communis L. OHF 333) was investigated. The plantlets were cultivated in vitro using Philips GreenPower LED research module. Four groups of LEDs emitting in white (W), red (R), blue (B), mixed (W:R:B:far-red = 1:1:1:1) (BR) and FL (control) lights were applied. Biometric parameters, content of photosynthetic pigments and chlorophyll fluorescence of the plants were measured after three four weeks passages under corresponding light treatment. Our results indicate that different LEDs specifically affect the growth and development of in vitro cultured pear plants. The highest fresh mass distinguishes the plants grown under white and blue LED light. There were also no significant variations in plantlet dry mass grown at the light sources studied. In plants grown under blue LED light, the highest values for plant height and length of lateral shoots are recorded. The highest number of lateral shoots is observed in white LED light, but a statistically proven difference reported only in the blue light variant. Plants cultivated under white LED light are distinguished by the largest number of leaves, followed by plants under blue and mixed light. The number of leaves in plants grown under red LED light is almost two times lower than that of white LED. The content of photosynthetic pigment is similar, except for the plants grown at red LED, which show a significant decrease in the content of chlorophyll and carotenoids.