Photosynthetic parameters and stem strength of Gerbera jamesonii ‘Bayadere’ plants were studied after foliar application with calcium chloride (0, 0.5, 1, and 1.5 g L-1) under natural light (NL), red light LEDs (R), blue light LEDs (B) and red + blue light LEDs (RB). Chlorophyll content increased under LED lights and foliar application with calcium chloride. The maximal quantum yield of PSII efficiency (Fv/Fm) and performance index (PI) reached the lowest value under NL conditions. The highest values of photosynthesis rate, stomatal conductance, and transpiration rate (E) were achieved by RB lighting. Under the RB light and calcium chloride spraying, the plants showed the lowest leaf nitrate content, compared to NL conditions. This resulted in the highest leaf nitrate content. The higher the nitrate content, the lower the stem strength. However, the leaf calcium content showed an opposite trend. Sprays of 1.5 g L-1 calcium chloride in combination with RB lighting significantly increased the flower stem strength and reduced stem bending, compared to non-treated plants. In summary, the RB lighting and foliar application with calcium chloride enhanced the growth and flower stem firmness of cut gerbera.
