Differential regulation of anthocyanin pigmentation by temperature in Cymbidium orchid flowers

和其他植物一样，蕙兰花瓣和萼片中的花青素积累也受到低温的刺激。另一方面，唇瓣内的酶活性不是由低温促进的，而是由高温促进的。以三种蕙兰杂交品种（红宝石之眼‘金星’、樱花‘春野’、谷花‘三唇M_rchen’）为研究对象，研究了这种有趣的花青素色素沉着的温度差异调控机制。在高温处理开始时（31ºC光照/23ºC暗温，16 h光周期），花期唇瓣色素沉着模式随花蕾发育阶段的不同而变化。在幼嫩花蕾中，高温对唇瓣色素沉着有强烈的刺激作用。即使高温仅持续3天，花青素在唇瓣的积累也不可逆。随着花芽发育，高温的影响逐渐减弱。高温对发育良好花蕾唇瓣花青素积累的影响很小或没有影响。在谷花“三唇青”花的两个唇瓣中，花青素的色素沉着也与真唇瓣中一样，在高温下得到促进。高温诱导的大花蕙兰杂种唇瓣花青素色素沉着似乎与授粉和/或去势诱导的唇瓣着色不同。花青素生物合成途径的步骤在唇瓣和其他花被之间受温度的差异调节仍有待确定。

As in other plants, anthocyanin accumulation in the petals and sepals of Cymbidium flowers is also stimulated by low temperature. On the other hand, that in the labellum is promoted not by low temperature but by high temperature. This interesting differential regulatory mechanism of anthocyanin pigmentation by temperature was investigated with three Cymbidium hybrids (Ruby Eyes 'Golden Star', Sazanami 'Haru-no-umi', Valley Flower 'Three Lip M_rchen'.Pigmentation pattern of the labellum at anthesis varied with developmental stages of flower buds at the onset of high temperature treatment (31ﾟC light/23ﾟC dark temperatures, 16 h photoperiod). In younger flower buds, labellum pigmentation was strongly stimulated by high temperature. Anthocyanin accumulation in the labellum was induced irreversively even by high temperatue for only 3 days. The influence of high temperature decreased with flower bud development. High temperature had little or no effect on the anthocyanin accumulation in the labellum of well-developed flower buds. Also in the two labellum-like petals of Valley Flower 'Three Lip M_rchen' flowers, anthocyanin pigmentation was promoted by high temperature as in the true labellum. The high temperature-induced stimulation of anthocyanin pigmentation in the labellum of Cymbidium hybrids seems to be a different phenomenon from pollination- and/or emasculation-induced labellum coloration.The step(s) of the anthocyanin biosynthetic pathway which is differentially regulated between the labellum and the other perianths by temperature remains to be determined.