High accumulation of soluble sugars in deep supercooling Japanese white birch xylem parenchyma cells
High accumulation of soluble sugars in deep supercooling Japanese white birch xylem parenchyma cells
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DOI：
10.1111/j.1469-8137.2007.02025.x
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发表时间：
2007-01-01
期刊：
影响因子：
9.4
通讯作者：
Fujikawa, Seizo
中科院分区：
文献类型：
--
作者：
Kasuga, Jun;Arakawa, Keita;Fujikawa, Seizo
研究了日本白色白桦（Betula platyphylla var.比较了可溶性糖对深度过冷机制的影响，深度过冷使细胞内的水在极低温度下长期保持液态。通过高效液相色谱法（HPLC）分析了两种组织中的可溶性糖，并通过组织学观察每个组织中薄壁细胞的占有率来估计细胞中糖的浓度。用差热分析和低温扫描电镜分别测定了薄壁细胞的相对熔点和平衡熔点，结果表明：在木质部和皮层薄壁细胞中，蔗糖、棉子糖和水苏糖的含量在冬季增加，而果糖和葡萄糖的含量全年变化不大。此外，没有发现糖对任一组织是特异性的。结合HPLC分析、组织学观察和熔点分析的结果，证实了木质部细胞中的糖浓度远高于皮层细胞，认为木质部细胞中较高的可溶性糖浓度可能通过降低成核温度而促进了木质部细胞的深过冷。
Seasonal changes in the accumulation of soluble sugars in extracellular freezing cortical parenchyma cells and deep supercooling xylem parenchyma cells in Japanese white birch (Betula platyphylla var. japonica) were compared to identify the effects of soluble sugars on the mechanism of deep supercooling, which keeps the liquid state of water in cells under extremely low temperatures for long periods.Soluble sugars in both tissues were analyzed by high-performance liquid chromatography (HPLC), and the concentrations of sugars in cells were estimated by histological observation of occupancy rates of parenchyma cells in each tissue. Relative and equilibrium melting points of parenchyma cells were measured by differential thermal analysis and cryoscanning electron microscopy, respectively.In both xylem and cortical parenchyma cells, amounts of sucrose, raffinose and stachyose increased in winter, but amounts of fructose and glucose exhibited little change throughout the entire year. In addition, no sugars were found to be specific for either tissue. Combined results of HPLC analyses, histological observation and melting point analyses confirmed that the concentration of sugars was much higher in xylem cells than in cortical cells.It is thought that the higher concentration of soluble sugars in xylem cells may contribute to facilitation of deep supercooling in xylem cells by depressing the nucleation temperature.