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The Secret of the Black Dahlia
by Helen Fields 胡德良 译
| Gardeners can choose from more than 20,000 varieties of dahlias, including whites, yellows, deep reds, and magentas. But the rarer black dahlias are especially alluring. Now, a team of researchers in Austria has turned the eye of science on what makes a dahlia black. The team collected 14 varieties of black dahlia—with names such as "Black Barbara," "Arabian Night," "Karma Choc" (left), and "Tisa" (right)—and five varieties with tamer colors, then extensively analyzed their petals. They measured the activity of enzymes that make pigments, investigated gene expression, and measured the pigments themselves. Their conclusion: The black color comes from high levels of anthocyanins, the pigments that—at lower levels—also give orange and red dahlias their colors. The team reports in BMC Plant Biology that they think that most black dahlias raise their anthocyanin levels by blocking an enzyme in the pathway that makes flavones, another molecule that has the same precursor as anthocyanins. If scientists could figure out that trick, they might be able to engineer dahlias to make more black varieties. |
园艺爱好者可以从两万多个品种中选择大丽花，包括白色的、黄色的、深红色的和洋红色的。但是，比较罕见的黑大丽花是特别迷人的。现在，一个奥地利的研究团队将科学的目光转向大丽花是如何变黑的。研究小组搜集了14种黑色大丽花——它们的名字为“黑色芭芭拉”、“阿拉伯之夜”、“命运巧克力（见左图）”和“苔萨（Tisa见右图）”等，还搜集了五个颜色更加沉闷的品种，然后广泛地分析了它们的花瓣。研究人员测量了色素制造酶的活性，研究了基因表达，并且计量了色素本身的含量。他们的结论是：黑色来自于花青素，较少量的这种色素也可以使大丽花呈现出橙色和红色。研究小组在《BMC植物生物学》杂志上报道说：他们认为，多数黑大丽花通过阻断制造黄酮的通路来提高花青素的水平。黄酮是另外一种分子，跟花青素有着相同的前体。如果科学家们能够弄清其中的诀窍，他们就有可能通过生物工程制造出更多的黑大丽花。 |
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