Norikoshi Ryo, Yamada Kunio, Niki Tomoko, Ichimura Kazuo
NARO Institute of Floricultural Science, Fujimoto, Tsukuba, Ibaraki, 305-8519, Japan.
School of Agriculture, Tokyo University of Agriculture, Funako, Atsugi, Kanagawa, 243-0034, Japan.
Planta. 2015 Dec;242(6):1467-77. doi: 10.1007/s00425-015-2385-2. Epub 2015 Aug 28.
The role of mannitol differs from that of glucose, fructose and sucrose in sepal cell expansion associated with flower opening in Delphinium × belladonna. Sepals of Delphinium × belladonna are colored and much larger than the petals. To determine whether the role of mannitol in sepal growth associated with flower opening differs from those of ubiquitous metabolic sugars including glucose, fructose and sucrose, we investigated changes in cell number, subcellular concentrations of soluble carbohydrates, and osmotic potential in sepals during flower opening in Delphinium × belladonna cv. Bellamosum. The number of epidermal cells in the sepals did not increase from the stage when sepal pigmentation started, whereas the cell area increased during flower opening, indicating that petal growth during flower opening depends on cell expansion. Mannitol concentrations in the vacuole at three different stages were approximately 100 mM, which were much higher than the other carbohydrate concentrations, but they decreased slightly at open stage. In contrast, mannitol concentration in the cytoplasm was 56 mM at bud stage, but it increased to 104 mM at open stage. Glucose and fructose concentrations in the vacuole at open stage increased to 45 and 56 mM, respectively. Total osmotic potential in apoplast and symplast, which was partially due to soluble carbohydrates, was almost constant during flower opening. Therefore, mannitol may be acting constitutively as the main osmoticum in the vacuole where it may contribute to the maintenance of the osmotic balance between the cytoplasm and vacuole in open flowers. The role of mannitol differs from those of glucose, fructose, and sucrose in sepal cell expansion in Delphinium × belladonna.
在与毛茛科翠雀属植物‘贝拉多娜’花朵开放相关的萼片细胞扩展过程中，甘露醇的作用不同于葡萄糖、果糖和蔗糖。毛茛科翠雀属植物‘贝拉多娜’的萼片有颜色，且比花瓣大得多。为了确定甘露醇在与花朵开放相关的萼片生长中的作用是否不同于包括葡萄糖、果糖和蔗糖在内的常见代谢糖类，我们研究了毛茛科翠雀属植物‘贝拉多娜’品种‘贝拉莫苏姆’花朵开放期间萼片中的细胞数量、可溶性碳水化合物的亚细胞浓度以及渗透势的变化。从萼片开始色素沉着的阶段起，萼片中表皮细胞的数量就没有增加，而在花朵开放期间细胞面积增加，这表明花朵开放期间花瓣的生长依赖于细胞扩展。在三个不同阶段，液泡中的甘露醇浓度约为100 mM，远高于其他碳水化合物的浓度，但在开放阶段略有下降。相比之下，细胞质中的甘露醇浓度在花蕾期为56 mM，但在开放阶段增加到104 mM。开放阶段液泡中的葡萄糖和果糖浓度分别增加到45 mM和56 mM。质外体和共质体中的总渗透势在花朵开放期间几乎保持恒定，部分原因是可溶性碳水化合物。因此，甘露醇可能在液泡中持续作为主要渗透剂起作用，在开放花朵中它可能有助于维持细胞质和液泡之间的渗透平衡。在毛茛科翠雀属植物‘贝拉多娜’的萼片细胞扩展过程中，甘露醇的作用不同于葡萄糖、果糖和蔗糖。
