中文摘要：

以福建省平潭岛海岸不同演化阶段草丛沙堆表面典型沙生植物老鼠艻为对象,研究其叶水势日变化特征及其影响因素.结果表明：老鼠艻叶水势日变化以＂W＂型为主,午间出现短暂升高现象.发育阶段沙堆表面老鼠艻叶水势日均值较稳定阶段高,且夜间水分恢复能力更强;老鼠艻叶水势与大气水势和相对湿度呈显著正相关,与气温呈显著负相关,但与不同深度土壤水势无显著相关性;发育阶段沙堆丘间地老鼠艻叶水势在10：00—16：00皆高于迎风坡和背风坡,迎风坡除10：00和12：00外皆低于背风坡.不同坡位叶水势日变异程度表现为背风坡〉迎风坡〉丘间地,但无显著差异.沙堆迎风坡老鼠艻叶水势与大气水势和相对湿度呈显著正相关,与气温呈显著负相关;沙堆背风坡和丘间地老鼠艻叶水势与气象因子有一定相关性,但不显著.

英文摘要：

Diurnal variation and its influencing factors of leaf water potential（ ψl） of Spinifex littoreus on the nebkhas in two succession periods were measured on the coast of Pingtan Island,Fujian Province. The results showed that the diurnal variation of ψlof S. littoreus mainly demonstrated a ‘W＇curve pattern,with a temporary rise at midday. The mean ψlof S. littoreus on the nebkhas at developing stage was higher than that at stabilizing stage,and recovered better during the night. ψl of S. littoreus was positively related to the atmospheric water potential（ ψa） and relative humidity,negatively related to air temperature,but had no significant correlation with the soil water potential at different depthes. ψlof S. littoreus on the interdune depression at developing stage was higher than that on the windward slope and on the leeward slope from 10： 00 to 16： 00,and that on the windward slope was lower than that on the leeward slope all day long except at 10： 00 and at 12： 00.The variation of ψlof S. littoreus on the leeward slope was higher than that on the windward slope,and the minimal variation was found on the interdune depression,without statistical significance. ψl of S. littoreus on the windward slope was positively correlated with ψa and relative humidity,while negatively correlated with air temperature. ψlof S. littoreus on the leeward slope and the interdune depression were correlated with meteorological factors,but they had no significant relationship.