Study On The Mechanism Of Leaf Color Formation In Ornamental Kale (Brassica Oleracea Var. Acephalea F. Tricolor)

Twenty one cultivars of ornamental kale were used to study the content of chlorophyll,carotenoid and anthocyanin in inner (colored leaves) and outer leaves (non-colored leaves), theactivity of anthocyanin biosynthesis enzyme in order to explore the relationship between leaf colorand pigment profile. The effect of pigment content and temperature on chlorophyll fluorescencecharacteristics of those21cultivars were also studied. High performance liquid chromatography(HPLC-DAD) and HPLC electrospray ionization mass spectrometry (HPLC-ESI-MS) methods wereemployed for quantitative and qualitative analysis of anthocyanins. The results were shown asfollows.The content of total chlorophyll, and carotenoid in outer leaves for all cultivars graduallydecreased during developmental stages. The chlorophyll content in outer leaves decreased apparentlyat ornamental stage. Total chlorophyll content in inner leaves decreased more quickly than that inouter leaves. The carotenoid content of inner leaves at bolting stage was higher than that ofornamental stage. Pigment contents were also different among different cultivars. Anthocyanin wasnot detectable in all cultivars at seedling stage. It could only be detected in inner leaves of purplecultivars at ornamental and bolting stage. Flavonoids was detectable in yellow cultivars. The changesof flavonoids content is not regular between ornamental and bolting stage. Overall flavonoids contentof inner leaves was higher than that of outer leaves. The anthocyanin composition in all purplecultivars was same, with only cyanidin detected as a aglycone. Three predominant anthocyaninsdeteced in purple ornamental kale were cyanidin-3-diglucoside-5-glucoside, cyanidin-3-(sinapoyl)-diglucoside-5-glucoside, and cyanidin-3-(sinapoyl)-(feruloyl) diglucoside-5-glucoside. The maincoloring pigment of yellow varieties are flavonoids, flavonols and a small amount of carotenoids.The activity of anthocyanin biosynthesis related enzymes were changed at color transition stage.With the increase of anthocyanin content, CHI activity was kept at a high level with a minor change,however the activity of PAL was firstly increased and then reduced at last. DFR activity were differentamong cultivars. Change of DFR activity in purple cultivars was similar as that of anthocyanin.The chlorophyll fluorescence parameters were influenced by temperature. There was a littledecrease in Fv/Fm, Y(II) and ETR for all cultivars with the decrease of temperature. Y(NPQ) andNPQ increased in Nagoya red and Osaka red with the decrease of temperature, not for other cultivars. This indicates that these two cultivars have good heat dissipation mechanisms, relatively strongresistance to cold.