Determination of Optimal UV Stress Period before Harvest for Maximizing Phytochemical Production of Kale Cultivated in Plant Factories

antioxidant capacity;chlorophyll fluorescence image;total flavonoid content;total phenolic content;633

농업생명과학대학 식물생산과학부 ;

University:서울대학교 대학원

关键词: antioxidant capacity;    chlorophyll fluorescence image;    total flavonoid content;    total phenolic content;    633;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/137613/1/000000146418.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

Recently ultraviolet-B (UV-B) has been used to improve the secondary metabolites of kales grown in plant factories. However, it is still unclear whether UV-B stress will be effective in enhancing the secondary metabolites at harvest because most of UV-B stresses were applied at early growth stage. The objectives of this study were to analyze the secondary metabolites accumulation at uneven UV-B distributions in leaves of matured kales at harvest stage using spatial chlorophyll fluorescence images and to determine the optimal UV stress period before harvest for maximizing secondary metabolites production of kales cultivated in plant factories. Kales (Brassica oleracea L. cv ;;Manchoo Collad’) were grown at a temperature of 20oC, photosynthetic photon flux density of 350 μmol∙m-2∙s-1, and photoperiod of 16 h/8 h (light/dark) in a plant factory, and harvested at 42 days after transplanting. Light-emitting diodes (LED) with red:blue:white = 8:1:1 were used. At first, spatial chlorophyll fluorescence (Fv/Fm) of the plants at different UV-B intensities in leaves at harvest were measured by a leaf fluorescence image analyzer. And then, the plants were additionally exposed to 4.2 W·m-2 UV-B for 4 h a day from 5, 4, 3, 2, and 1 days before harvest (T5, T4, T3, T2, and T1, respectively). Fresh and dry weight, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity were compared at harvest. In the same leaves, Fv/Fm values were different according to locations exposed to different UV-B intensities, while no significances were observed in TFC and TPC. This indicated that accumulation of secondary metabolites is not always proportional to the local Fv/Fm values. UV-B stress decreased fresh and dry weights and increased secondary metabolites. TFC, TPC, and antioxidant capacity at T5 were significantly higher than any other treatments but dry weight was the lowest. Considering total amounts of secondary metabolites, T2 was the optimum treatment period, in which the concentration was lower but the dry weight higher than T5. This is because the dry weight had a greater effect on the total amount than the secondary metabolites concentration induced by UV-B radiation. To maximize the secondary metabolites of kales with UV-B treatment, it would be more efficient to use short-term stresses to minimize the loss of fresh and dry weights.