自然和人工生境被子植物枝木质部结构与功能差异

Differences in anatomical structure and hydraulic function of xylem in branches of angiosperms in field and garden habitats

水是植物生存与生长的基础条件,水分有效性影响植物木质部解剖结构、水力功能,使之形成特定的适应特征。因此,对比自然与人工生境中同一植物的水力功能与解剖结构差异,有助于理解植物对水分环境的适应机理。该研究以湿润区三角槭(Acer buergerianum)、青冈(Cyclobalanopsis glauca)和女贞(Ligustrum lucidum)为研究材料,对比分析了自然和人工生境中各物种的栓塞抗性(导水率损失50%时的水势(P_(50)))、输水效率(比导率(Ks))和解剖结构(导管直径(D)、导管壁厚(T)、导管密度(N)、木质部密度(WD)、厚度跨度比(t/b)^(2))特征,探究了同生境种内与跨生境、跨物种水平的效率-安全权衡关系,量化分析了水力功能与解剖结构的关系。结果发现:1)3种被子植物在自然生境中Ks更大,P_(50)更小,与其更大的D、更小的(t/b)^(2)有关。2)同生境种内Ks与P_(50)不存在权衡。3)功能性状和解剖结构相关分析表明:同生境种内D与P_(50)不存在显著的相关关系;除自然生境女贞外,T、(t/b)^(2)均与P_(50)正相关。相对于人工生境,在水分有效性低或无额外浇灌的自然生境中,植物通过增大导管直径显著提高其输水效率,从而避免水势下降、降低潜在栓塞风险。

Aims Water is essential for plant survival and growth.Water availability affects the anatomical structure and hydraulic function of xylem,and finally makes trees form specific acclimating characters.Therefore,comparing the differences of hydraulic function and anatomical structure between plants growing in field and garden habitats,can facilitate a better understanding on the acclimation of plants to water conditions.Methods We compared hydraulic safety(water potential at 50%loss of conductivity,P_(50)),hydraulic efficiency(specific hydraulic conductivity,Ks)and xylem anatomy(vessel diameter(D),double thickness of vessel wall(T),vessel density(N),xylem density(WD)and thickness-to-span ratio of vessels((t/b)^(2))),between field and garden plants of Acer buergerianum,Cyclobalanopsis glauca and Ligustrum lucidum.We also analyzed the differences of the relationship between xylem hydraulic function and anatomical structure in field and garden habitats.Important findings We found that:1)The Ks was higher and P_(50) was lower in field habitat of the three angiosperms,which were related to the larger D and smaller(t/b)^(2).2)The intraspecific correlation analysis between Ks and P_(50) showed that there were no efficiency-safety trade-offs.3)Intraspecific correlation analysis of anatomical structure and functional traits showed that there was no significant correlation between D and P_(50);except for L.lucidum in garden habitat,the T and(t/b)^(2) of the other trees was positively correlated with P_(50).Comparing to garden habitat,plants in field habitat with low water availability or no additional irrigation increased their diameter of vessels to improve water transport efficiency,so as to avoid the decrease of water potential and effectively reduce the potential risk of embolism.