Effect of Cold Stress on Carotenoids in Kale Leaves (Brassica oleracea)

BACKGROUND: Kale (Brassica oleracea) biosynthesizes various phytochemicals including glucosinolates, flavonoids, and carotenoids. Phytochemicals of plants are influenced by light, temperature, carbon dioxide, and growing conditions. Specifically, carotenoids are affected by temperature, light, and oxygen. The aim of this study was to investigate the effect of cold stress (day/night: $25^{\circ}C/20^{\circ}C$, $20^{\circ}C/15^{\circ}C$, $15^{\circ}C/10^{\circ}C$) on carotenoids in kale leaves. METHODS AND RESULTS: Kale was grown in pots for up to 50 days after sowing (DAS) in a greenhouse. For cold acclimation experiments, kale grown in growth chambers for 3 days and was subjected to low temperature for 4 days. The conditions maintained in the growth chambers were as follows: photoperiod, 12/12 h (day/night); light, fluorescent; and relative humidity, 60%. Carotenoid (lutein, ${\alpha}-carotene$, zeaxanthin, ${\beta}-carotene$) contents were analyzed by high-performance liquid chromatography (HPLC). The total carotenoid content gradually increased during cold acclimation for 3 days. When kale was subjected to cold stress, the total carotenoid content was high at $25^{\circ}C/20^{\circ}C$ treatment, but low at $15^{\circ}C/10^{\circ}C$ treatment. The total carotenoid content of kale leaves continuously grown in greenhouse decreased from 50 to 57 DAS (1,418 and 1,160 mgkg-1 dry wt., respectively). The lutein, ${\alpha}-carotene$, and ${\beta}-carotene$ contents were very low and the zeaxanthin contents were very high at $15^{\circ}C/10^{\circ}C$ treatment. When kale was subjected to cold stress, the ratio of individual to the total carotenoid contents of kale leaves was 4553% for -carotene and 210% for zeaxanthin. CONCLUSION: The ${\beta}-carotene$ and zeaxanthin contents in kale leaves indicate their sensitiveness toward cold stress.

저온처리가 케일(Brassica oleracea)잎 내 Carotenoid에 미치는 영향