Anatomical Study On Secondary Xylem In 19 Species Of Sterculiaceae

This study used SEM to investigate vestured pits of 10 genus 19 species of Sterculiaceae. The photograph of SEM photos were measured by the Carnoy2.0 software to quantity characteristic index of border pits and richness index of vestured pits. The main results were as follows:1. The existence and distribution of vestured pits in secondary xylem of 19 species within SterculiaceaeThe SEM image of the secondary xylem of 10 genus 19 species within Sterculiaceae showed that various forms of vestured pits occurred in the secondary xylem of the 19 species of Sterculiaceae. Dot-shaped, dentate and irregular massive vestures were obversed in all the 19 species. Statistical analysis of richness index of vestured pits found that vestured pits varied considerably in distribution and micromorphology which might be one of the reasons why the previous researchers did not observe vestured pit within Sterculiaceae’s secondary xylem. Besides, statistical analysis of the richness indexes of intervascular vestured pits in the secondary xylem of 19 species within Sterculiaceae found that the mean of 3 richness indexes, namely, the frequency of the vestured vessel inner pit aperature, the frequency of the vestured pit chamber and the frequency of the vestured outer pit aperature varied considerably in different species. The standard deviations of richness indexes were larger than the mean, which suggests that vestured pits scatteredly dustrubyted in vessel elements of study species.2. The correlation between richness indexes of vestured pitsThe variance analysis and multiple comparison of the 3 richness index by means of SPSS found that the mean of the frequency of the vestured vessel inner pit aperature is larger significantly than that of the frequency of the vestured outer pit aperature and the frequency of the vestured pit chamber, the means of frequency of the vestured vessel outer pit aperature and the frequency of the vestured pit chamber had no significant differences. Partial correlation analysis showed that only the frequency of the vestured vessel outer pit aperature and the frequency of the vestured pit chamber had very significant positive correlation within 3 richness indexes.3. The correlation between the quantitative features of the bordered pits and richness indexes of the vestured pitsThe stepwise regression analysis between the 3 richness indexes of the vestured pits and 11 quantitative features of the bordered pits showed that the frequency of the vestured vessel outer pit aperature had notable correlation with the shortest axis of the inner pit aperture, the establishment of the model can be expressed by YFVOA=23.886+10.114XSAIA(R2=0.237, F=6.58, P=0.02,0.01<P<0.05); the frequency of the vestured vessel inner pit aperature had very notable correlation with vertical pit membrane diameter, the longest axis of the outer pit aperture, the shortest axis of the outer pit aperture, the shortest axis of the inner pit aperture and pit aperture area per pit membrance area, the establishment of the model can be expressed by YFVIA=-29.706+21.091XDh-19.709XLAOA-64.778XSAOA+10.309XSAIA+4.546XFap (R2=0.761, F=8.278, P=0.001, P<0.01);the frequency of the vestured vessel pit chamber had notable correlation with the shortest axis of the outer pit aperture, the establishment of the model can be expressed by YFVPC=71.391-34.045XSAOA(R2=0.280, F=6.603,P=0.020, 0.01<0.05). Therefore, presumably, the richness of vestured pits had notable correlation with the quantitative features of the vestured pits.4. The vestured pits’ significance of the study on the classification and growth habit within SterculiaceaeWe found that similar pits type in the same genus had contribution to the study on the classification of Sterculiaceae. On the other hand,11 species Sterculiaceae that distributed in the tropics had higher pits’frequency than other 8 species which distributed in the subtropical. It proved that vestured pits played an active role in water transportation in the warm humid heat or dry condition.5. Phylogenetic and functional significance of vestured pits within SterculiaceaeThis study found that the 10 genus 19 species of Sterculiaceae are characterised by stable and significant vestured pit, which is not in accordance with the previous experiment. Therefore, the point on the homogeneity of non-vestured pits in core families of Malvales, namely, Sterculiaceae, Malvaceae, Bombacaceae and Tiliaceae is untenable. The hypothesis that vestured pit can enhance the cohesion of moisture and prevent embolism was supported by our study in that the frequency of the vestured vessel inner pit aperature of Sterculiaceae was highest.