| In this study,the new growth layers(the new formed secondary xylem)were demarcated from Rhizophora stylosa and Kandelia candel branches collected in 10 different continuous time spans within one year under a microscope since Rhizophora stylosa and Kandelia candel were characterized by growth ring in the secondary xylem.The quantitative wood anatomical features in new growth layers developed in 10 different continuous time spans was observed and measured by means of microscopy,and variations in soil physicochemical factors corresponding to formation period of new growth layers in 10 different continuous time spans within one year were determined as well.The monthly variations in anatomical characteristics of intervessel pits of two study species were observed and measured by scanning electron microscope,and the corresponding monthly variations in soil physicochemical factors were determined and the corresponding monthly variations in meteorologic data were collected as well.Some conclusions were drawn as follows:The relationship between the quantitative wood anatomical features in new growth layers developed in 10 different continuous time spans within one year and corresponding soil physicochemical factors.The quantitative anatomical features of vestured vessel outer aperature and vestured pit chamber in new growth secondary xylem in every month of one year was observed and measured by scanning electron microscope(SEM),and variations in soil physicochemical factors corresponding to formation period of new growth secondary xylem in every month of one year were determined as well,and variations in soil physicochemical factors corresponding to meteorological data for each month of one year.The main conclusions obtained through statistical analysis method are as follows:1)The relationship between monthly variations in soil physicochemical factors within one year and corresponding monthly variations in meteorological data was analysized by stepwise multiple regression analysis.The results showed:the soil contents of K,Na,Mg,Zn,Ca,Cl-,the total salt content and soil pH value in Rhizophora stylosa sampling spots increased with the increase of the monthly mean maximum temperature.the soil contents of Mn,Fe,Ca in Kandelia candel sampling spots increased with the increase of monthly mean maximum temperature,total soil salt content in Kandelia candel spots decreased with increase of the monthly rainfall.Presumably the monthly mean maximum temperature and the monthly rainfall had effect on variations of salt content in soil physicochemical factors.2)The morphological features of secondary xylem in two mangrove species was observed by means of scanning electron microscope(SEM).The results showed the ecological adaptation of the two mangrove species is very similar.Vestured pits and ray cells with starch granules were presumly contribute to conductive safety.3)The relationship between variations in soil physicochemical factors in 10 different continuous time spans within one year and the corresponding quantitative vessel anatomical features in new growth layers developed in 10 different continuous time spans was analysized by canonical correlation analysis(CCA)in Rhizophora stylosa spots.The results showed tangential pore diameter,radial pore diameter and solitary pore ratio of secondary xylem of Rhizophora stylosa decreased with the increase of total salt content and the Na contents in the soil,vessel cluster size,conducting area and ray area increased with the increase of total salt content and the Na contents of soil,the results showed the trends that the vessel diameter is smaller and vessel grouping index is higher with the increasing total soil salt content and the soil contents of Na,presumably variations of the quantitative vessel anatomical features enhance the safety of water transport in high soil salinity environments.Radial pore diameter of Rhizophora stylosa increased with the increase of the soil contents of K,Vessel elements of Rhizophora stylosa showed a larger trend with the increase of the content of K,presumably the content of Na and the content of K had effect on secondary xylem with checks and balances.Ray height and Ray width of Rhizophora stylosa increased with the increase of the soil contents of Ca,Fiber of Rhizophora stylosa showed a trend of larger with the increase of the content of Ca,presumably this trend may be an effective way to indirectly promote water transmission.4)The relationship between variations in soil physicochemical factors in 10 different continuous time spans within one year and corresponding to the quantitative vessel anatomical features in new growth layers developed in 10 different continuous time spans was analysized by canonical correlation analysis(CCA)in Kandelia candel sampling spots.The results showed tangential pore diameter,pore area,ray height and ray area of Kandelia candel increased with the increase of the soil contents of organic matter and total nitrogen.Vessel and Fiber of Kandelia candel showed a trend of larger with the increase of the content of organic matter and total nitrogen,presumably favorable environment and high nutritive soil conditions is conducive to the growth of Kandelia candel.Pore area and vessel cluster size increased with the increase of the soil contents of total salt,solitary pore ratio would decrease with total salt content of soil increasing,Vessel of Kandelia candel showed a trend of larger and higher vessel grouping index with the increase of the soil contents of total salt,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 Kandelia candel based on the viewpoints of ecological wood anatomy,which might be a adaptive strategy for S.caseolaris to adjust its xylem vessel anatomy to the variable soil salt contents within one year.Ray height,ray width and ray area increased with the increase of the soil contents of Ca,K,ray height,ray width and ray area would decrease with the Na contents of soil increasing;pore area,fiber wall thickness would decrease with pH of soil increasing,which might be a adaptive strategy for Kandelia candel to adjust tidal wave and storm surge.5)The relationship between variations in soil physicochemical factors in every mouth of one year and corresponding to the quantitative anatomical features of vestured vessel outer aperature and vestured pit chamber in new growth secondary xylem in every month of one year was analysized by stepwise regression analysis for two mangrove plants.The results showed:The longest axis of the outer aperture,the longest axis of the inner aperture in new growth secondary xylem of Rhizophora stylosa in every month of one year decrease with the the soil contents of total nitrogen increasing,frequency of vestured vessel inner aperature of Rhizophora stylosa decrease with the soil contents of total salt increasing;the shortest axis of the inner aperture in new growth secondary xylem of Kandelia candel in every month of one year increased with the increase of the soil contents of total salt,frequency of the lining of the catheter and frequency of vestured vessel outer aperature in new growth secondary xylem of Kandelia candel in every month of one year increased with the increase of the soil contents of organic matter.Because of the limitations of the experiment,the ecological mechanism between soil physicochemical factors in every mouth of one year and corresponding to the quantitative anatomical features of vestured vessel outer aperature and vestured pit chamber needs further study.In conclusion,the changes in the anatomical characteristics of secondary xylem from two mangrove plants were the results of acclimating changes in their habitats,which tended towards coordination in structure-function-ecology under the adverse conditions. |
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