对 100% 、40% 和 8% 自然光照条件下一年四季观光木( Tsoongiodendron odorum Chun) 幼树茎干液流密度(SFD)以及叶片蒸腾速率(Tr)和气孔导度(Gs)的日变化规律进行了比较,并对 SFD 与 Tr、Gs 及部分环境因子的相关性进行了分析。 结果表明:一年四季观光木的 SFD、Tr 和 Gs 均随光照的减弱而降低。 在不同光照条件下,一年四季观光木的 SFD 均呈昼高夜低的日变化规律,且 SFD 日均值和日峰值均在 100% 自然光照条件下最高、在 8% 自然光照条件下最低。 在 100% 和 8% 自然光照条件下 SFD 的日变化趋势基本一致,多数情况下在液流启动时即达到峰值;而在 40% 自然光照条件下其日变化曲线则为“单峰型”,峰值出现在 9:15 至 13:30。 除春季外,其他季节在不同光照条件下 SFD 日均值和日峰值总体上均有显著(P<0. 05)或极显著(P<0. 01)差异。 夏季在 100% 自然光照条件下 Tr 的日变化曲线呈“双峰型”,其他季节在不同光照条件下 Tr 的日变化曲线均呈“单峰型”。 在 40% 和8% 自然光照条件下不同季节 Gs 的日变化曲线也呈“单峰型”,且其峰值出现时间与 Tr 基本相同;而在 100% 自然光照条件下,冬季 Gs 的日变化曲线也为“单峰型”,但在其他季节则呈“双峰型”,并出现明显的“午休”现象。 相关性分析结果表明:在不同光照条件下一年四季观光木的 SFD 与叶片 Tr 均呈显著或极显著正相关;但与叶片 Gs 的相关性在不同季节及不同光照条件下有一定的差异。 在不同光照条件下,一年四季观光木 SFD 与叶片水汽压亏缺、大气温度及光合有效辐射强度(PAR)呈正相关, 与大气相对湿度呈负相关;其中,与 PAR 的相关性均达到显著或极显著水平。 研究结果显示:在不同光照条件下,PAR 是影响观光木 SFD 四季变化的最主要环境因子。

The daily change rules of sap flux density (SFD) of Tsoongiodendron odorum Chun saplings and its transpiration rate ( Tr) and stomatal conductance( Gs) of leaf under 100% , 40% and 8% of natural light conditions in four seasons of a year were compared, and also, the correlation of SFD with Tr, Gs and some environmental factors was analyzed. The results show that SFD, Tr and Gs of T. odorum in four seasons of a year decrease with light reducing. Under different light conditions, SFD of T. odorum in four seasons of a year appears a daily variation regularity of high in day time and low in night time, and daily mean and peak values of SFD all are the highest under 100% of natural light condition and the lowest under 8% of natural light condition. The daily variation trends of SFD are basically identical under conditions of 100% and 8% of natural light, and the peak value presents at starting time of sap flux under most conditions. While that of SFD under 40% of natural light condition appears the “single-peak type” and the peak value appears at 9:15 to 13:30. Except spring, daily mean and peak values of SFD under different light conditions in other seasons generally have significant ( P < 0. 05 ) or extremely significant (P<0. 01) differences. The daily change curve of Tr under 100% of natural light condition in summer appears the “double-peak type”, while that under different light conditions in other seasons all appear the “single-peak type”. The daily change curve of Gs under conditions of 40% and 8% of natural light in four seasons also appears the “ single-peak type” and the appearance time of peak value is basically the same as that of Tr. While, under 100% of natural light condition, the daily change curve of Gs is also the “ single-peak type” in winter but that is the “ double-peak type” in other seasons with obvious “ midday depression “. The correlation analysis result shows that SFD under different light conditions in four seasons of a year has significant or extremely significant positive correlation with Tr of leaf, but the correlation between SFD and Gs has a certain difference among different seasons or light conditions. Under different light conditions, SFD of T. odorum in four seasons of a year has a positive correlation with leaf vapor pressure deficit, air temperature and photosynthetically active radiation intensity (PAR), but a negative correlation with relative air humidity, in which, the correlation with PAR reaches the significant or extremely significant levels. It is suggested that PAR is the most important environmental factor for affecting on SFD of T. odorum in four seasons under different light conditions.