Cramer Viki A, Schmidt Susanne, Stewart George R, Thorburn Peter J
School of Environmental Science, Murdoch University, Murdoch, WA 6150, Australia.
Tree Physiol. 2002 Oct;22(14):1019-26. doi: 10.1093/treephys/22.14.1019.
It is predicted that dryland salinity will affect up to 17 Mha of the Australian landscape by 2050, and therefore, monitoring the health of tree plantings and remnant native vegetation in saline areas is increasingly important. Casuarina glauca Sieber ex Spreng. has considerable salinity tolerance and is commonly planted in areas with a shallow, saline water table. To evaluate the potential of using the nitrogenous composition of xylem sap to assess salinity stress in C. glauca, the responses of trees grown with various soil salinities in a greenhouse were compared with those of trees growing in field plots with different water table depths and groundwater salinities. In the greenhouse, increasing soil salinity led to increased allocation of nitrogen (N) to proline and arginine in both stem and root xylem sap, with coincident decreases in citrulline and asparagine. Although the field plots were ranked as increasingly saline-based on ground water salinity and depth-only the allocation of N to citrulline differed significantly between the field plots. Within each plot, temporal variation in the composition of the xylem sap was related to rainfall, rainfall infiltration and soil salinity. Periods of low rainfall and infiltration and higher soil salinity corresponded with increased allocation of N to proline and arginine in the xylem sap. The allocation of N to citrulline and asparagine increased following rainfall events where rain was calculated to have infiltrated sufficiently to decrease soil salinity. The relationship between nitrogenous composition of the xylem sap of C. glauca and soil salinity indicates that the analysis of xylem sap is an effective method for assessing changes in salinity stress in trees at a particular site over time. However, the composition of the xylem sap proved less useful as a comparative index of salinity stress in trees growing at different sites.
据预测，到2050年，旱地盐碱化将影响澳大利亚多达1700万公顷的土地，因此，监测盐碱地区树木种植和残余原生植被的健康状况变得越来越重要。海滨木麻黄具有相当强的耐盐性，通常种植在浅层盐碱地下水位的地区。为了评估利用木质部汁液的含氮成分来评估海滨木麻黄盐胁迫的潜力，将温室中在不同土壤盐分条件下生长的树木的反应与田间不同地下水位深度和地下水盐分条件下生长的树木的反应进行了比较。在温室中，土壤盐分增加导致茎和根木质部汁液中脯氨酸和精氨酸的氮分配增加，同时瓜氨酸和天冬酰胺减少。尽管根据地下水盐分和深度将田间地块按盐分增加进行了排序，但仅田间地块之间瓜氨酸的氮分配存在显著差异。在每个地块内，木质部汁液成分的时间变化与降雨、降雨入渗和土壤盐分有关。降雨和入渗少以及土壤盐分高的时期，对应着木质部汁液中脯氨酸和精氨酸的氮分配增加。在计算降雨已充分入渗以降低土壤盐分的降雨事件之后，瓜氨酸和天冬酰胺的氮分配增加。海滨木麻黄木质部汁液的含氮成分与土壤盐分之间的关系表明，分析木质部汁液是评估特定地点树木盐胁迫随时间变化的有效方法。然而，事实证明，木质部汁液的成分作为不同地点生长树木盐胁迫的比较指标不太有用。
