Changes in the localization and levels of starch and lipids in cambium and phloem during cambial reactivation by artificial heating of main stems of Cryptomeria japonica trees
Changes in the localization and levels of starch and lipids in cambium and phloem during cambial reactivation by artificial heating of main stems of Cryptomeria japonica trees
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DOI：
10.1093/aob/mcq185
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发表时间：
2010-12-01
期刊：
影响因子：
4.2
通讯作者：
Funada, Ryo
中科院分区：
文献类型：
--
作者：
Begum, Shahanara;Nakaba, Satoshi;Funada, Ryo
树木的形成层重新激活发生在冬末到早春，此时光合作用很少或几乎不存在。储备材料对于树木的木材形成可能很重要。研究了冬季局部加热的柳杉树干从形成层休眠到木质部分化开始的整个过程中，淀粉和脂质（以液滴形式）在形成层和韧皮部中的定位和大致水平以及淀粉颗粒的数量。通过对共焦激光扫描显微镜获得的光学数字图像进行图像分析，确定淀粉和脂质（作为液滴）的定位和大致水平以及淀粉颗粒的数量。与未加热的茎相比，局部加热诱导柳杉茎较早形成层再激活和木质部分化。从形成层休眠到加热茎中木质部分化的开始，根据图像上的相对面积确定的淀粉和脂质（作为液滴）各自的定位和水平存在明显的变化。在加热的茎中，从形成层重新激活到木质部分化开始，淀粉颗粒的水平和数量下降。从形成层重新激活到加热茎木质部分化开始，形成层中脂滴所占的相对面积显着减少。结果清楚地表明，冬季加热茎中，从形成层重新激活到木质部分化开始，形成层和韧皮部细胞中储存淀粉颗粒的水平和数量以及形成层中脂质（作为液滴）的水平下降。观察结果表明，日本柳杉可能需要淀粉和脂滴作为形成层细胞分裂和木质部分化的能量来源。
Cambial reactivation in trees occurs from late winter to early spring when photosynthesis is minimal or almost non-existent. Reserve materials might be important for wood formation in trees. The localization and approximate levels of starch and lipids (as droplets) and number of starch granules in cambium and phloem were examined from cambial dormancy to the start of xylem differentiation in locally heated stems of Cryptomeria japonica trees in winter.Electric heating tape was wrapped on one side of the stem of Cryptomeria japonica trees at breast height in winter. The localization and approximate levels of starch and lipids (as droplets) and number of starch granules were determined by image analysis of optical digital images obtained by confocal laser scanning microscopy.Localized heating induced earlier cambial reactivation and xylem differentiation in stems of Cryptomeria japonica, as compared with non-heated stems. There were clear changes in the respective localizations and levels of starch and lipids (as droplets) determined in terms of relative areas on images, from cambial dormancy to the start of xylem differentiation in heated stems. In heated stems, the levels and number of starch granules fell from cambial reactivation to the start of xylem differentiation. There was a significant decrease in the relative area occupied by lipid droplets in the cambium from cambial reactivation to the start of xylem differentiation in heated stems.The results showed clearly that the levels and number of storage starch granules in cambium and phloem cells and levels of lipids (as droplets) in the cambium decreased from cambial reactivation to the start of xylem differentiation in heated stems during the winter. The observations suggest that starch and lipid droplets might be needed as sources of energy for the initiation of cambial cell division and the differentiation of xylem in Cryptomeria japonica.