Sara Humphrey

Sara Humphrey

Effect of Broadband White Light Supplemented with Far-Red and Blue LEDs on Intumescence Injury of Compact Tomato Transplants


Sara Humphrey, Marlon Retana Cordero, Celina Gómez


Dr. Celina Gómez


College of Agricultural and Life Sciences


Intumescence is a cultivar-specific physiological disorder characterized by blister-like tumors on the surface of leaves, petioles, and stems of susceptible crops such as tomato (Solanum lycopersicum). Plants seem to develop intumescence injury in environments that lack ultraviolet (100 to 400 nm) radiation, but far-red (700 to 800 nm) and blue (400 to 500 nm) light have been shown to help mitigate this disorder. Although strategies to suppress intumescence injury with narrowband light-emitting diodes (LEDs) are promising, broadband white (400 to 700 nm) LEDs are often preferred for indoor plant production. Therefore, the objective of this study was to evaluate the effects of supplementing broadband white light with far-red and blue LEDs on intumescence injury and growth of six compact tomato cultivars susceptible to this disorder. ‘Patio’, ‘Sweet n’ Neat Yellow’, ‘Little Bing’, ‘Yellow Canary’, ‘Little Napoli’, and ‘Camaro’ transplants were grown in a growth chamber for 3 to 4 weeks under an average daily light integral of 13 mol·m‒2·d‒1 (200 µmol·m‒2·s‒1 for 18 h·d–1) provided by 1) broadband white (W); 2) W supplemented with blue (WB); 3) W supplemented with blue and far-red (WBFR); or 4) narrowband blue and red LEDs supplemented with far-red (BRFR). Across cultivars, WBFR and BRFR mitigated intumescence injury almost completely. ‘Camaro’ and ‘Little Napoli’ developed the highest degree of intumescence, with up to 69% and 46% of their leaves affected under W, and 53% and 35% under WB, respectively. All other cultivars had less than 40% of their leaves affected by intumescence. Our results also indicated that older leaves develop more intumescence than younger leaves, suggesting changes in susceptibility depending on the plant age. Although both treatments supplemented with far-red helped mitigate intumescence, transplants under WBFR were generally more compact than those under BRFR, which is a positive quality attribute that integrates height and biomass. WBFR also had the greatest relative leaf area, averaging 17% more than BRFR. In contrast, depending on the cultivar, WBFR produced 5% to 25% larger leaves than BRFR, which could contribute to whole-plant photosynthesis after transplanting. Although our findings have important implications for commercial growers and indoor home gardeners considering using the cultivars evaluated in our study, further work is needed to investigate the effectiveness of WBFR and BRFR at mitigating intumescence beyond the propagation stage, as it appears that plant growth and development help regulate the susceptibility to this disorder.


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