Effects of LED light spectra and intensity on winter citrus nursery production

Authors: BISI, RAYANE - University Of Florida; ALBRECHT, UTE - University Of Florida; Niedz, Randall; Bowman, Kim

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2026
Publication Date: 4/30/2026
Citation: Bisi, R.B., Albrecht, U., Niedz, R.P., Bowman, K.D. Effects of LED light spectra and intensity on winter citrus nursery production. PLOS ONE. 21(4): e0347764. 2026. https://doi.org/10.1371/journal.pone.0347764.
DOI: https://doi.org/10.1371/journal.pone.0347764

Interpretive Summary: This study looked at how different colors and brightness levels of LED lights can help young citrus trees grow better during the winter, when there’s less natural sunlight. The main question was: how do red, blue, white, and far-red LED lights, used alone or in combination, affect when new buds start growing and how long and how large the shoots get? Two types of rootstocks were tested – Carrizo (a cross between sweet orange and trifoliate orange) and Rich 16-6 (trifoliate orange) - both grafted with Washington Navel orange. The trees were grown in a greenhouse where the temperature stayed the same, and they got natural sunlight during the day. Extra LED lights were added so that the plants got 16 hours of light each day. Different combinations of light colors and brightness levels were used, and eight different measurements were made, including how many buds grew, the size of the shoots and leaves, and the amount of chlorophyll in the leaves. The results were clear: both the color and brightness of the lights made a big difference. Blue and white light, especially when bright, encouraged more buds to grow. Red and far-red light on their own slowed down bud growth. The best shoot growth happened when red, blue, and white light were combined at their brightest. Far-red light alone didn’t help much, but when used with red or white light, it made shoots longer and leaves bigger. Blue and white light produced the greenest leaves (highest chlorophyll levels), while far-red led to the least green. In short, the right combination of LED colors and brightness can help citrus nurseries grow healthier trees faster during winter. These results could help growers produce more plants even when natural daylight is short.

Technical Abstract: This study investigated the effects of supplemental light-emitting diode (LED) light spectra and intensity on the winter growth of grafted citrus nursery plants. The primary objective was to determine how different combinations of red, blue, white, and far-red LED light, applied at varying intensities, influence vegetative budbreak and scion shoot growth in young citrus trees during short winter days. The experiment used two citrus rootstocks, Carrizo (a hybrid of sweet orange and trifoliate orange) and Rich 16-6 (trifoliate orange), each budded with Washington Navel orange. Plants were grown in a temperature-controlled greenhouse and received natural sunlight, with supplemental LED lighting used to extend the photoperiod to 16 hours. The study employed a 4-factor response surface design, testing multiple combinations of light spectra and intensity. Eight plant growth and physiological responses were measured, including percentage budbreak, scion shoot length and diameter, rootstock diameter, internode length, leaf area, scion dry weight, and leaf chlorophyll index. Results showed that both the quality and intensity of supplemental LED light significantly affected all measured responses. Blue and white light, particularly at higher intensities, increased vegetative budbreak in both rootstocks, while red and far-red light reduced budbreak. The greatest scion shoot growth was observed when red, blue, and white light were combined at maximum intensity. Far-red light alone did not enhance growth, but when combined with red or white light, it further increased shoot elongation and leaf area. Chlorophyll content was highest under blue and white light and lowest under far-red light. These findings demonstrate that optimizing supplemental LED light spectra and intensity can improve winter nursery production of grafted citrus by enhancing budbreak and shoot growth. The results provide a basis for refining light management strategies in commercial citrus nurseries to increase propagation efficiency during periods of limited natural light.