Effects of Illumination on Growth and Development and Quality of Cut Flowers of Eustoma grandiflorum (Raf.) Shinners

Lucetta, a cultivar of Eustoma grandiflorum (Raf.) Shinners, was subjected to treatments of different light intensities (100%, 85%, 70% and 55% of natural light intensity) and different light durations (10-h natural lighting, 12-h natural lighting, 12-h natural lighting + 2-h LED lighting, 12-h natural lighting + 4-h LED lighting), and then its plant height, crown width, stem thickness, stalk thickness, total flower number, flowering period and growth situation were analyzed. The results show that E. grandiflorum (Raf.) Shinners is sensitive to the changes in light intensity. Under 85% of natural light intensity (40 000-50 000 lux), E. grandiflorum (Raf.) Shinners grew faster, bloomed earlier with more flowers, and was taller, thicker, more robust, higher in yield, larger in pedicel length, and better in cut flower quality, without rosette phenomenon. Long-term exposure to low-intensity light would led to slow growth, thin stalk, delayed flowering, low yield and reduced cut flower quality in E. grandiflorum (Raf.) Shinners. The illumination duration of more than 12 h could promote the differentiation of flower buds, increase the plant height, increase the length of pedicels of E. grandiflorum (Raf.) Shinners. Extending the light duration by 2-4 h at night, that is, 14-16-h of illumination was the most ideal illumination time for the growth of E. grandiflorum (Raf.) Shinners. A longer photoperiod could promote the growth and bring forward the blooming of E. grandiflorum (Raf.) Shinners. The longer the illumination time, the higher the plant. The optimum illumination time was between 14 and 16 h. When the illumination duration was shorter than 12 h, the growth of E. grandiflorum (Raf.) Shinners was retarded, and its flowering was also delayed.