关键词: 20 cm蒸发皿, 日光温室, 滴灌, 灌溉制度

Abstract: 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 (F_d) 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 F_d (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.

Key words: 20 cm pan, solar greenhouse, drip irrigation, irrigation scheduling.