Lighting source as cause of changes in cucumbers’ physiology and morphology

The demand of fresh fruits and vegetables is growing. Therefore cultivation of them is essential all year round. The growth in the dark period of a year is not imaginable without artificial lighting sources. Therefore the experiments were carried out to investigate the effects of three different lighting sources on the growth of cucumbers at the early stages of development. Plants were grown in the polycarbonate greenhouse under three different lighting sources: Led cob Helle top LED 280, induction lamp and high pressure sodium lamp Helle magna. Cucumbers were grown in 16h photoperiod with PAR at the tips of plants 200 ± 20 µmol m-2 s -1 . Plant growth parameters, specific leaf area, pigments, phenols and flavonoids content in leaves, leaf light reflection parameters were determined. Results showed that cucumber plants grown under Led cob Helle top LED 280 in average were smaller, with less chlorophyll, carotenoids and phenols, but leaves have higher chlorophyll a and b ratio and specific leaf area in comparison with traditionally used in greenhouses High Presure Sodium Lamps (HPSL). Cucumber plants grown under Induction lamp in average were shorter, but with larger leaf area, with higher chlorophyll and carotenoids content, but decreased phenols content in comparison with HPSL. Lichtenthaler index 1 (LIC1) and NDVI are useful for assessing the physiological state of cucumber plants. Despite the fact that the plants grow well and develop normally under all lamps, the results show that sodium lamps are the most suitable for cucumbers. Further research is needed to adjust LED lighting for cucumber cultivation