中文摘要：

了解木兰科植物的水分利用特点对提高其迁地保护的成功率具有重要作用。利用TDP探针（热消散探针）测定2种木兰科植物长蕊木兰（Alcimandra cathcartii）和醉香含笑（Michelia macclurei）的树干液流, 分析树干液流与环境因子的关系。结果表明：2树种整树蒸腾的日变化均为单峰格型，但夜间仍有液流发生；在1月长蕊木兰单位断面积液流通量（Fd）日峰值［（25.00±7.35） g·m-2·s-1］明显比醉香含笑高［（6.35±1.46） g·m-2·s-1］，在7月和1月长蕊木兰的Fd日平均值（6：00—18：00）也明显高于醉香含笑；2树种日蒸腾耗水量对环境因子的响应随季节变化而异，在干季（10月和1月）2树种对环境因子的响应比雨季（4月和7月）更明显；单位断面积日蒸腾耗水量可以有效区分个体间或种间的耗水差异；长蕊木兰的生理耗水量比醉香含笑大，在迁地保护时应注意长蕊木兰对水分需求较大的生理特征。

英文摘要：

To understand the water use characteristics of Magnoliaceae is of significance to improve its survival rate in exsitu conservation. By using thermal dissipation probe, this paper studied the dynamics of the diurnal and seasonal sap flow densities of Alcimandra cathcartii and Michelia macclurei as well as the relationships between the dynamics and environmental factors in Guangzhou of South China. A single peak pattern was observed in the diurnal variation of the transpiration of the two species, but there was still a visible sap flow after sunset. In January 2009, the daytime maximum sap flux density per unit basal area （Fd） of A. cathcartii （25.00±7.35 g·m-2·s-1） was obviously higher than that of M. macclurei （6.35±1.46 g·m-2·s-1）; in July 2008 and January 2009, the daytime mean Fd （6：00-18：00） of A. cathcartii was also obviously higher than that of M. macclurei. Partial correlation analysis indicated that the responses of the transpiration of the two species to environmental factors varied with seasons, being stronger in dry season （October and January） than in wet season （April and July）. The wholeday transpiration per unit area at breast height was an effective indicator to reveal the differences in the diurnal water consumption for transpiration among the individuals and the tree species. The water consumption of A. cathcartii was greater than that of M. macclurei, and thus, more attention should be paid to A. cathcartii in its exsitu conservation because of its high physiological demand for water.