UV-B Supplementation to Mitigate Intumescence Injury of Tomato Seedlings Grown Under White LEDs in a Plant Factory

다국어 초록 (Multilingual Abstract)

When growing tomato (Solanum lycopersicum Mill.) seedlings in ultraviolet (UV) light deficit environment, like a plant factory with artificial lighting (PFAL), intumescence can occur on leaf and stem surfaces. Supplementation of UV-B light can suppress the intumescence, and also can modulate morphology and photomorphogenic responses in plants. Therefore, researching UV-B supplementation should be required for suppressing intumescence injury and finding out morphological and growth reactions for each tomato cultivar cultivated in PFAL. Seeds of ‘B-blocking’ and ‘DoterangDia’, which is representative cultivars of rootstocks and scions for grafted tomato transplants, respectively were sown and subsequently cultivated in a PFAL with white LEDs at a light intensity of 180 μmol m<SUP>-2</SUP>·s<SUP>-1</SUP> for 16 h·d<SUP>-1</SUP> and air temperature of 25/20°C and relative humidity of 70/90% (photo-/dark periods) for 21 days. UV-B light was supplemented to each cultivar at 0 (control), 0.05, 0.1, or 0.15 W·m<SUP>-2</SUP> for three hours per day. Intumescence incidence was measured for all the leaflets longer than 1 cm. Intumescence incidence of ‘B-blocking’ decreased significantly in UV-B supplementation treatments and less than 1% of ‘B-blocking’ plants grown at supplemental UV-B intensity of 0.1 W·m<SUP>-2</SUP> and 0.15 W·m<SUP>-2</SUP> showed an intumescence incidence. Leaf area and dry weights of shoot and root increased at UV-B intensity of 0.05 and 0.1 W·m<SUP>-2</SUP> but decreased at 0.15 W·m<SUP>-2</SUP> comparing to those in control. ‘DoterangDia’ plants in all treatments showed low rates of intumescence incidence compared to that of ‘B-blocking’, but they also showed decreased intumescence incidence as the UV-B intensity increased. The stem length of ‘DoterangDia’ plants increased at UV-B intensity of 0.05 W·m<SUP>-2</SUP> compared to that in control. Results suggest that the response to supplementary UV-B light is cultivar-specific and the proper intensity for ‘B-blocking’ and ‘DoterangDia’ would be 0.1 W·m<SUP>-2</SUP> and 0.05 W·m<SUP>-2</SUP>, respectively. The different cultivar-specific responses to UV-B light between scion and rootstock cultivars would be due to the genetic differences among their major breeding resources.