Pate John, Shedley Erica, Arthur David, Adams Mark
Department of Botany, The University of Western Australia, Nedlands, Western Australia 6907, Australia Fax: +61-8-93801001, , , , , , AU.
Oecologia. 1998 Dec;117(3):312-322. doi: 10.1007/s004420050664.
Spontaneous bleeding of sugar-rich sap from cambial-deep incisions in the bark of trunks was demonstrated for Eucalyptus globulus and other eucalypts across a range of localities and seasonal conditions in south-west Australia. High levels of sucrose and raffinose (up to 31% w/v total sugars) were present in the exudates, and upward and downward gradients in exudate sugar concentrations were recorded between samples obtained at different heights up trunks of E. globulus. The data indicated a phloem origin for the exudates, with source:sink pressure gradients driving translocation. Concentration ratios of sugars to amino acids were consistently lower in exudate from upper (distal) than basal regions of trunks, suggesting preferential partitioning of nitrogen upwards towards the trunk apex. A comparison of phloem and xylem sap composition from one plantation over a season showed nitrate in xylem but not phloem and substantial amounts of sodium, and high concentrations of chloride and sulphate relative to phosphate in xylem and phloem. Phloem sap sampled across a range of 29 contrasting plantations of E. globulus at peak stress (autumn) showed great inter-site variability in concentrations of amino acids, sulphur, sodium and certain trace elements and in C:N and Na:K ratios of sap. Carbon isotope ratios (δC) were strongly correlated with sugar concentrations of the sap samples from these and other plantations. Use of sap compositional attributes of phloem and δC values of translocated carbon is suggested for assessing the current nutritional condition and water status of E. globulus plantings.
在澳大利亚西南部的一系列地点和季节条件下，对蓝桉和其他桉树进行了实验，结果表明，从树干树皮形成层深处切口处会自然渗出富含糖分的汁液。渗出液中含有高水平的蔗糖和棉子糖（总糖含量高达31% w/v），并且在蓝桉树干不同高度采集的样本之间，记录到了渗出液糖浓度的上下梯度。数据表明渗出液起源于韧皮部，源 - 库压力梯度驱动着物质运输。树干上部（远端）渗出液中糖与氨基酸的浓度比始终低于基部区域，这表明氮优先向上分配至树干顶端。对一个种植园在一个季节内韧皮部和木质部汁液成分的比较显示，木质部中有硝酸盐而韧皮部中没有，还有大量的钠，并且木质部和韧皮部中氯化物和硫酸盐的浓度相对于磷酸盐较高。在压力峰值期（秋季），对29个不同的蓝桉种植园采集的韧皮部汁液样本显示，氨基酸、硫、钠和某些微量元素的浓度以及汁液的C:N和Na:K比在不同地点之间存在很大差异。碳同位素比率（δC）与这些种植园以及其他种植园的汁液样本中的糖浓度密切相关。建议利用韧皮部汁液的成分属性和运输碳的δC值来评估蓝桉种植园当前的营养状况和水分状况。
