AUTHOR=Wang Shunli , Liu Xiaoting , Liu Xiaoning , Xue Jingqi , Ren Xiuxia , Zhai Yanning , Zhang Xiuxin 

TITLE=The red/blue light ratios from light-emitting diodes affect growth and flower quality of Hippeastrum hybridum ‘Red Lion’

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1048770

DOI=10.3389/fpls.2022.1048770

ISSN=1664-462X

ABSTRACT=<p>Light quality strongly impacts the growth and flower quality of ornamental plants. The optimum light quality for the growth and flowering of <italic>Hippeastrum</italic> remains to be validated. In the present study, we investigated the effect of the red/blue light ratio of LEDs on the growth and flowering quality of <italic>H. hybrid</italic> ‘Red Lion’. Two LEDs with red/blue light ratio of 1:9 (R<sub>10</sub>B<sub>90</sub>) and 9:1 (R<sub>90</sub>B<sub>10</sub>) were designed. LEDs of white light were the control. In the earlier vegetative and reproductive growth phase, R<sub>90</sub>B<sub>10</sub> increased the biomass of the bulbs, leaves, and flowers. Compared with the control and R<sub>10</sub>B<sub>90</sub> group, R<sub>90</sub>B<sub>10</sub> LEDs delayed flowering by 2.30 d and 3.26 d, respectively. Based on chlorophyll contents, photosynthetic capacity, chlorophyll fluorescence parameters, and carbohydrate contents, the photosynthesis rate was higher in the R<sub>10</sub>B<sub>90</sub> group. Optimal red and blue light intensity promoted the accumulation of carbohydrates and early flowering and prolonged the flowering period of <italic>H. hybrid</italic>. Microscopic analysis showed that stomatal density was high, and the number of chloroplasts was large in the R<sub>10</sub>B<sub>90</sub> treatment group, which enhanced photosynthesis. Particularly, R<sub>10</sub>B<sub>90</sub> promoted the expression of seven key genes related to chlorophyll synthesis. R<sub>10</sub>B<sub>90</sub> also promoted early overexpression of the <italic>HpCOL</italic> gene that promotes early flowering. Thus, higher blue light and 10% red light intensities promote early and extended flowering, while higher red light and 10% blue light promote vegetative plant growth but delay flowering.</p>