琵琶柴和沙拐枣茎的木质部结构的差异性及空间变异特征

Differences and spatial variation in the stem xylem structural traits of Reaumuria soongarica and Calligonum mongolicum

木质部结构性状是植物适应不同水分条件的基础,也是植物响应环境条件变化的核心属性之一。以西北荒漠区的典型灌木琵琶柴(Reaumuria soongarica)和沙拐枣(Calligonum mongolicum)为研究对象,对其木质部结构和水力功能性状进行对比分析,以期了解同一生境中不同物种的差异性或相似性,以及同一物种在不同环境条件下的木质部结构性状的可塑性。结果表明:(1)琵琶柴和沙拐枣的木质部结构性状存在显著差异,沙拐枣平均导管直径、脆弱性指数显著高于琵琶柴,而导管密度、导管分组指数则相反。(2)琵琶柴和沙拐枣的木质部结构性状随气候变化的规律具有差异,随年均降水量和干旱指数的增加,沙拐枣的平均导管直径与导管厚跨比显著下降,而琵琶柴的平均导管直径与导管厚跨比与之无关,仅理论导水率与年均降水量和干旱指数呈显著正相关关系。(3)琵琶柴木质部导水系统存在效率与安全的权衡,而沙拐枣中没有表现出效率和安全的权衡关系。(4)性状网络分析结果表明,琵琶柴和沙拐枣的中心性状均为平均导管直径,平均导管直径的变化介导了性状网络的变化。琵琶柴和沙拐枣的木质部结构性状存在显著差异,相对于沙拐枣,琵琶柴水分利用策略更加保守。

Xylem structure traits are the basis for plant adaptation to different water conditions and are core plant traits in response to changes in environmental conditions.The typical shrubs Reaumuria soongarica and Calligonum mongolicum in the northwest desert region were selected as the subjects for comparison between stem xylem structure and functional traits to understand the differences or similarities of different species in the same habitat and the xylem structure plasticity of the same species under different environmental conditions.The results showed that(1)Xylem structure traits of R.soongarica and C.mongolicum were significantly different.The mean vessel diameter and vulnerability index of C.mongolicum were significantly higher than those of R.soongarica,whereas the opposite was true for vessel density and vessel grouping index.(2)The patterns of xylem structure traits in response to climate change differed between R.soongarica and C.mongolicum.The mean vessel diameter and vessel thickness-to-span ratio of C.mongolicum significantly reduced with increasing mean annual precipitation and aridity index,whereas that of R.soongarica were unrelated,and only the theoretical hydraulic conductivity had a significant positive correlation with the mean annual precipitation and aridity index.(3)There was a trade-off between efficiency and safety in the xylem hydraulic conductivity system of R.soongarica,whereas none was observed in C.mongolicum.(4)The trait network analysis results indicated that the central traits of both R.soongarica and C.mongolicum were mean vessel diameters.Changes in mean vessel diameter mediate changes in the trait network.Xylem structure traits between R.soongarica and C.mongolicum were significantly different,with R.soongarica having a more conservative water use strategy than C.mongolicum.