酸枣荆条耗水特征及其茎木质部解剖构造

目的]研究酸枣和荆条耗水特征与其茎木质部解剖构造之间的关系,为中国北方干旱区造林树种的选择提供技术支持。方法]采用热扩散式液流探针(TDP)法对酸枣和荆条的树干液流进行监测,并于监测完成后,采用切片法,观察其茎木质部解剖构造。结果](1)不同季节2树种的耗水特征存在差异,与湿润季节相比,干旱季节两树种树干液流变化均具有较强的波动性,其日均液流速度和日均耗水量均较小;2树种相比,干旱季节时酸枣的最大液流速度、日均液流速度以及日均耗水量均显著大于荆条,而湿润季节与之相反。(2)就其茎木质部解剖构造而言,酸枣的导管形状大小比较均一,而荆条的导管形状大小参差不齐;酸枣的导管直径、长度、面积平均值及边材相对输导面积均小于荆条,而其导管密度大于荆条。(3)酸枣的相对输导率和脆性指数均小于荆条,说明酸枣的水分输导的有效性小于荆条,而其安全性和抗旱性大于荆条;另外,在湿润季节,二者的耗水特征主要取决于其水分输导的有效性,而在干旱季节,主要取决于其安全性和抗旱性,进而阐明了二者在不同季节表现出不同耗水差异的原因。结论]与荆条相比,酸枣的茎解剖构造更有利于其在干旱季节维持较高的树干液流,进而得以正常的生长,因此更适合于干旱区造林。

Water-Consumption Characteristics and Stem Xylem Anatomical Structure of Zizyphus Jujuba and Vitex Negundo var. Heterophylla

Objective] To study the relationships between water-consumption characteristics and stem xylem anatomical structures of Zizyphus jujuba and Vitex negundo var. heterophylla, in order to provide technical support for the selection of afforestation species in arid regions of North China.Methods] The water consumption characteristics of Z. jujubavar and V. negundo. var. heterophylla were studied with the thermal dissipation probe (TDP), and then the xylem anatomical structures of their stem were observed with slicing method.Results] (1) The water consumption characteristics were different for the two trees in different seasons. In dry season, there were more fluctuating changes both for the two trees as compared with the ones in wet season, and the averages of daily sap flow velocity and daily water consumption were lower. In dry season, the max of sap flow velocity and the average of daily sap flow velocity, and daily water consumption of Z. jujuba were all higher than the ones of V. negundo var. heterophylla. In wet season, these were vice versa. (2) As for xylem anatomical structure of stem, compared with the ones of V. negundo var. heterophylla, the shape and size of Z. jujuba vessel were more uniform. And the average of vessel diameter, vessel length, vessel area and the sapwood relative cross-sectional area of Z. jujuba were all lower than the ones of V. negundo var. heterophylla. Only the vessel density of Z. jujuba var. spinosa was higher than that of V. negundo var. heterophylla. (3) The relative conductivity and the vulnerability indexes of Z. jujuba were lower than the ones of V. negundo var. heterophylla. It showed that the water conduction efficacy of Z. jujuba was lower than that of V. negundo var. heterophylla, and the safety and drought resistance of Z. jujuba were all higher than those of V. negundo var. heterophylla. In wet season, their water-consumption characteristics were mainly determined by the efficacy of water conduction. In dry season, however, their water-consumption characteristics were mainly determined by the safety and drought resistance. These might be the reason that the difference of their water-consumption in different seasons.Conclusion] Compared with V. negundo var. heterophylla, stem xylem anatomical structure of Z. jujubavar was more capable to transport sap as high as possible, which can made it grow normally. So Z. jujuba was more suitable for the afforestation in arid regions.