利用电子探针技术观测果实组织钙原位分布(英文)

Application of electron probe to the observation of in situ calcium distribution in fruit tissues

【目的】矿质营养元素的组织分布可以反映元素的运输和利用特点,以钙元素为例,介绍一种利用电子探针结合图像处理的精确直观展示元素组织原位分布的分析方法。【方法】以成熟期‘怀枝’荔枝和‘砂糖橘’柑橘的果柄和果皮,及‘次郎’柿的果柄为材料,将真空下镀铂的果柄或果皮薄片在扫描电子显微镜下采集二次电子图像,同时用波谱仪采集钙X-射线信号分布图像。用Photoshop图像处理软件提取钙分布点阵图,将白色光点改为红色光点,将之与二次电子图像合并。【结果】合并的图像可以精确直观显示钙组织原位分布,发现果柄中韧皮部钙含量明显高于木质部,韧皮部中纤维细胞含钙低,而薄壁细胞含量高,并有大量的薄壁细胞内含有富钙颗粒(草酸钙结晶)。荔枝果皮的表皮含钙高,也有钙富集细胞,而柑橘果皮钙分布相对较均匀。【结论】电子探针分析结合图像处理是精确分析植物组织元素原位分布的有效手段。从果柄钙原位分布的结果看,钙有可能是通过韧皮部向果实运输。

【Objective】 Distribution of mineral nutrition in plant tissues reflects the patterns of nutrient transportation and utilization. Using calcium analysis in fruit tissues as an example, this paper demonstrates a method that combines electron probe microanalysis and image processing technique, which generates a direct view of in situ mineral distribution in plant tissues. 【Method】 Pedicels and pericarps of mature fruits of litchi ‘Huaizhi' and citrus ‘Shatangju' and pedicels of persimmon ‘Cilang' were used as materials for this study. Tissue slices coated with platinum were observed under scanning electron microscope equipped with an electron probe(wave dispersive spectroscopy, WDS). Secondary electron images and Ca-specific X-ray signal mapping images(Ca mapping image) were separately collected. The map of bright dots representing abundance of Ca was extracted using image processing Photoshop and combined with the secondary electron image. 【Result】 The combined image provided a direct view of detailed in situ Ca distribution in fruit tissues. In the pedicels of all the three fruit speciess, Ca abundance in the phloem is significantly greater than in the xylem. Within the phloem, fiber cells have the lowest Ca content, while the parenchyma cells contain higher calcium. Many of these cells have Ca-rich bodies(calcium oxalate crystals). The epiderm of litchi pericarp has high calcium and also contains Ca-rich bodies. Pericarp of citrus has a relatively even Ca distribution. 【Conclusion】 Electron probe combined with image processing technique provides an effective method for observing in situ nutrition distribution in plant tissues. According to the distribution pattern of Ca in fruit pedicel, it is suggested that Ca transport to fruit is likely through the phloem instead of xylem.