Xylem ray parenchyma cells in boreal hardwood species respond to subfreezing temperatures by deep supercooling that is accompanied by incomplete desiccation
Xylem ray parenchyma cells in boreal hardwood species respond to subfreezing temperatures by deep supercooling that is accompanied by incomplete desiccation
复制标题
DOI：
10.1104/pp.011601
复制
发表时间：
2003-02-01
期刊：
影响因子：
7.4
通讯作者：
Fujikawa, S
中科院分区：
文献类型：
--
作者：
Kuroda, K;Kasuga, J;Fujikawa, S
阔叶树种的木质部射线薄壁细胞(XRPC)对深过冷或胞外冷冻的反应是公认的。用低温扫描电子显微镜研究了五种北方硬木：沙柳Salix sachalinensis Fr.的XRPC的冷冻反应。Schmit、小叶杨、白桦。Var Japan onica Hara，Betula pubescens Ehrh.，和红木(Cornus Sericea)，其中XRPC已被报道通过细胞外冷冻来反应。低温扫描电子显微镜观察表明，木质部缓慢降温至-80℃时，导致大部分XRPC在细胞内冻结，这表明这些XRPC已经被深度过冷。相反，在白杨、白杨、毛竹和山茱萸的大多数XRPC中，缓慢降温到-80℃时会产生轻微的胞质收缩，但没有明显的细胞内冻结的证据，这表明这些XRPC可能通过细胞外冻结来响应。在这些XRPC中，假定细胞外冻结；然而，深度蚀刻显示在受限的局部区域明显形成细胞内冰晶。为了确认细胞内冻结的发生，我们在冷却后重新加热这些XRPC，并观察到由于重结晶而产生的非常大的细胞内冰晶。因此，我们研究的所有北方硬木中的XRPC都以深度过冷反应，并伴随着不完全干燥。从这些结果来看，XRPC深度过冷能力的限制似乎可能是硬木适应寒冷气候的限制因素。
It has been accepted that xylem ray parenchyma cells (XRPCs) in hardwood species respond to subfreezing temperatures either by deep supercooling or by extracellular freezing. Present study by cryo-scanning electron microscopy examined the freezing responses of XRPCs in five boreal hardwoods: Salix sachalinensis Fr. Schmit, Populus sieboldii Miq., Betula platyphylla Sukat. var japonica Hara, Betula pubescens Ehrh., and red osier dogwood (Cornus sericea), in which XRPCs have been reported to respond by extracellular freezing. Cryo-scanning electron microscopy observations revealed that slow cooling of xylem to -80degreesC resulted in intracellular freezing in the majority of XRPCs in S. sachalinensis, an indication that these XRPCs had been deep supercooled. In contrast, in the majority of XRPCs in P. sieboldii, B. platyphylla, B. pubescens, and red osier dogwood, slow cooling to -80degreesC produced slight cytorrhysis without clear evidence of intracellular freezing, suggesting that these XRPCs might respond by extracellular freezing. In these XRPCs exhibited putative extracellular freezing; however, deep etching revealed the apparent formation of intracellular ice crystals in restricted local areas. To confirm the occurrence of intracellular freezing, we rewarmed these XRPCs after cooling and observed very large intracellular ice crystals as a result of the recrystallization. Thus, the XRPCs in all the boreal hardwoods that we examined responded by deep supercooling that was accompanied with incomplete desiccation. From these results, it seems possible that limitations to the deep-supercooling ability of XRPCs might be a limiting factor for adaptation of hardwoods to cold climates.