Anatomical Study On Secondary Xylem Of 4 Mangrove Species And Their Garden Application

Four mangrove species (Sonneratia caseolaris, Bruguiera gymnoihiza, Rhizophora stylosa and Aegiceras corniculatum) were used to study the variations in anatomical features of secondary xylem in different time periods within a year and their adaptive significance to variable soil physicochemical factors in corresponding time. Soil physicochemical properties representing 8 different time periods within a year were determined. The anatomical characteristics of the secondary xylem of four mangrove species were studied in details in 8 time periods within a year by means of light microscopy and scanning electron microscopy through distinctive plant sectioning methods for sampling preparation. Variations in the quantitative wood anatomical features in four mangrove species were assessed in details. Relationships between soil physicochemical variables and the quantitative wood anatomical features were analyzed by means of statistical methods. The main conclusions are as follows:1. Vessel element diameter in S.caseolaris varies to some extend in 8 different time periods within a year based on PI values of tangential pore diameter and radial pore diameter that are 0.34 and 0.31. Presumably S.caseolaris is diffuse-porous wood characterized by occurrence of wide and narrow vessel elements, which can both efficiently and safely conduct water; Pit chambers of S.caseolaris in samples collected from 8 different time periods within a year are completely occluded by a net woerk of larger, branched vestures and frequency of vestured vessel outer aperature and frequency of vestured vessel pit chamber showed no difference in 8 different time periods within a year by LSD analysis (P>0.05), therefore, persistent occurrence of vestured vessel outer aperature and vestured pit chamber is the important guarantee to water transport in saline habitat based on functional explanation of vestured pits. The pore area in S.caseolaris in 8 different time periods within a year increased with the increase of soil organic matters determined in corresponding time by stepwise regression analysis (Y=72.412XOM-336.801. R2=0.577, P=0.029＜0.05), which indicated larger pore area that are conducive to more efficient water transport might develop one of structural basis to promote growth in saline habitat; Fiber wall thickness in S.caseolaris in 8 different time periods within a year increased with decrease of total soil salt content (Y=-0.123Xtsc+5.184, R2=0.586, P=0.027<0.05) and fiber lumen width decreased with increase of total soil potassium content (Y=-16.985XTK+47.454, R2=0.709. P=0.009<0.01) by stepwise regression analysis, presumably total soil salt content and total soil potassium content had effect on mechanic support with checks and balances, thinner fibre wall thickness in higher total soil salt content might be more prone to cavitation and block the water transport, however, higher total soil potassium content can prevent S.caseolaris from cavitation to some extent.2. B.gymnorrhiza, of which the pore diameter has some changes within a year (The PI value of the tangential diameter is 0.35, and the PI value of the radial diameter is 0.34).Presumably,B..gymnorrhiza has wide and narrow vessel elements,it is good for coordination between water transporting safety and water transporting efficiency;The progressively regression analysis showed that the diameter of secondary xylem of B.gymnorrhiza increases with the increase of pH of soil in different time periods of one year (RD:Y=8.114XpH+381.835XTN-69.68,R2=0.916,PpH=0.027<0.05,PTN=0.016<0.05; TD:Y=14.731XpH-52.792,R2=0.539,P=0.038<0.05),vessel pore area would increase with the increase of pH value of soil (Y=1031.584XpH-5183.154,R2=0.675,P=0.012< 0.05).its vessel cluster size would decrease with pH value of soil increasing (Y=-0.328XpH+3.697,R2=0.762,P=0.005＜0.01),this result indicates that the higher soil pH could promote pore size, it could be a structural basis for promoting the growth of B.gymnorrhiza in saline environment, but it will decrease vessel cluster size so that it is not beneficial to water transporting safety;The fiber wall thickness of B.gymnorrhiza would increase with the increase in soil organic matter content in different time periods of one year(Y=0.175XOM-2.523.R2=0.593,P= 0.025<0.05),the results suggested that soil organic matter content has a positive effect on the mechanical strength.and it is conducive to the transport of water.3.The pore size of R.stylosa has also some variation during a year (the PI value of tangential pore diameter is0.36. the radial pore diameter is 0.41, the pore area is 0.53).which show that R.stylosa not only have wide vessel but also have narrow vessel.which can both efficiently and safely conduct water;By stepwise regression analysing.we can find that the vessel cluster size of secondary xylem of R.stylosa would decrease with pH value of soil increasing in different times of a year (Y--0.204XPH+2.603,R2=0.509.P=0.047<0.05).and its vessel wall thickness would decrease with pH value of soil increasing (Y=-1.893XpH+17.866,R2=0.537,P=0.039< 0.05).the results showed that the pH value of soil could promote the ability of mechanical support,but it is not beneficial to the water transporting safety;The pore density of R.stylosa would increase with total salt content of soil and total potassium conten of soil decreasing in different times of a year,and increase with total nitrogen contenincreasing (Y=181.006XTN-0.818XTSC-99.485XTK+253.745,R2=0.996,PTk=0< 0.01;PTSC=0.001<0.01;PTNn=0.009<0.01).according to the results.the conductive efficiency of R.stylosa effected by variaty factors.such as total salt content of soil.total potassium conten of soil and total nitrogen conten.4.The pore size of A.corniculatum has some variation during a year (the PI value of tangential pore diameter is0.38, the radial pore diameter is 0.41, the pore area is 0.46),which show that A.corniculatum not only have wide vessel but also have narrow vessel,which can both efficiently and safely conduct water;The radial pore diameter of secondary xylem of A.corrmiculatum would decrease with the total potassium conten of soil increasing in different times of a year by stepwise regression analysis (Y=-56.02Xtk+149.857.R2=0.684,P=0.011<0.05).the results showed that the total potassium conten of soil could effect the pore diameter and be beneficial to the validity of water transport;Fiber lumen width would increase with soil organic matter increasing and decrease with pH value increasing (Y=0.259XOM-1.74XpH+8.123,R2=0.860PpH= 0.004<0.01;POM=0.034<0.05).the results showed that the soil organic matter and pH value of soil would be the opposite on effecting the mechanical supporting ability of A. corniculatum.the increasing of soil organic matter is not beneficial to the water transport safety due to vessel embolization.but the pH value of soil would alleviate it.5.Mangrove plants which is potential landscape species in coastal cities not only have high ecological value,but also form the distinctive mangrove landscape in beach.