海桑次生木质部导管解剖特征与土壤理化因子年内动态变化的关系研究

Relationship between the Vessel Anatomical Features of Sonneratia caseolaris Branches and Dynamic Changes of Soil Physicochemical Factors within One Year

为揭示海桑次生木质部导管解剖特征随土壤理化因子年内动态变动而变化的适应机制,该研究利用海桑具有生长轮的特点,通过显微技术界定了海桑采样枝条一年内10个不同连续时间段形成的新"生长层"(新形成的次生木质部),观测了10个不同连续时间段新"生长层"的导管解剖特征,并对10个新"生长层"形成阶段所对应的土壤理化因子数量特征进行了测定,用逐步回归法分析了10个不同连续时间段海桑新"生长层"管孔数量解剖特征与对应土壤理化因子数量特征之间的关系。结果显示:(1)10个不同连续时间段海桑形成新"生长层"管孔数量特征指标,除相邻管孔间接触壁长占比无显著差异外,其他8项指标包括管孔径向直径、管孔弦向直径、导管壁厚、导管长度、管孔密度、单孔率、导管聚合度和相邻管孔间接触壁长等均具有显著差异(P<0.05);多重比较显示,10个不同连续时间段海桑形成新"生长层"管孔数量特征8项指标具不同程度的变动。(2)海桑新"生长层"形成阶段(10个不同连续时间段)土壤理化因子,包括土壤有机质含量、土壤全氮含量、土壤全磷含量、土壤pH值和土壤全盐量等5项指标均具有显著差异(P<0.05);多重比较显示,海桑新"生长层"形成阶段(10个不同连续时间段)土壤理化因子指标均具有不同程度变动。(3)10个不同连续时间段海桑形成新"生长层"的管孔数量解剖特征,与所对应新"生长层"形成阶段土壤理化因子数量特征的逐步回归分析表明,随着土壤全盐含量的升高,海桑导管弦向直径和导管聚合度同时呈显著增大趋势(P<0.05)。研究表明,海桑在一年内不同连续时间段,随土壤全盐量增加,土壤渗透势将增大,水分在次生木质部导管中输导的安全性将下降,而海桑导管分子随一年内不同连续时间段土壤全盐量的增加呈增大趋势,根据木材生态解剖学的观点,水分输导的安全性将进一步降低,但导管聚合度随一年内不同连续时间段土壤全盐量的增加而增大,具有增进水分输导安全性的作用,这可能是海桑对土壤盐含量变化的生态适应策略。

In this study,the new growth layers(the new formed secondary xylem)were demarcated from Sonneratia caseolaris branches collected in10different continuous time spans within one year under a microscope since S.caseolaris was characterized by growth ring in the secondary xylem.The quantitative vessel anatomical features in new growth layers developed in10different continuous time spans was observed and measured by means of microscopy,and variations in soil physicochemical factors corresponding to formation periods of new growth layers in10different continuous time spans within one year were determined as well,the relationship between the quantitative vessel anatomical features in new growth layers developed in10different continuous time spans within one year and corresponding soil physicochemical factors was analyzed by stepwise multiple regression to explore variations in quantitative vessel anatomical features of S.caseolaris branches with dynamic changes of soil physicochemical factors within one year and their adaptive significance.The results showed:(1)ANOVA indicated that8quantitative vessel anatomical feature indexes including radial vessel diameter,tangential vessel diameter,intervessel wall thickness,vessel element length,vessel density,solitary vessel index,vessel grouping index and intervessel wall length in new growth layers developed in10different continuous time spans within one year showed significant difference(P<0.05),with exception of intervessel contact fraction,which showed no significant difference(P>0.05).LSD multiple comparisons indicated that8quantitative vessel anatomical feature indexes which show significant difference(P<0.05)varied to some extend.(2)ANOVA indicated that Soil physicochemical factors including soil organic matter content,soil total nitrogen content,soil total phosphorus content,soil pH value and total soil salt content corresponding to the formation period of new growth layers in10different continuous time spans within one year show significant difference(P<0.05),and LSD multiple comparisons indicated that5soil physicochemical factor indexes varied to some extend.(3)The stepwise multiple regression analysis between the quantitative vessel anatomical features in new growth layers developed in10different continuous time spans within one year and corresponding soil physicochemical factors indicated the trends that the tangential vessel diameter is larger and vessel grouping index is higher with the increasing total soil salt content which show significant difference at0.05level.We drew some In conclusions,from the relationship between the vessel anatomical features of S.caseolaris branches and dynamic changes of soil physicochemical factors in10different continuous time spans within one year,the osmotic potential increased in the soil with the increase of soil salt content within one year,which led to reduction of the safety of water transport in the secondary xylem vessels of S.caseolaris,and the safety of water transport might decrease further if the larger tangential vessel diameter developed under conditions of higher soil salt content within one year.However,the higher vessel grouping index with the increasing soil salt content within one year would ensure safety of water transport in xylem vessel of S.caseolaris based on the viewpoints of ecological wood anatomy,which might be an adaptive strategy for S.caseolaris to adjust its xylem vessel anatomy to the variable soil salt content within one year.