| Casparian strip was frequently regarded as a specific structure of tracheophyta, which appeared as a lignified and suberized narrow zone encircling the radial and transverse walls of the endodermal cells. In this dissertation, the occurrence together with structure, chemical composition and the development of Casparian strips in the foliar endodermis of Pimts bungeana were studied by means of confocal microscope, TEM, FTIR and so on in the foliar endodermis of Pinaceae. The main results are as follows.1. The fluorescence micrographs of the isolates obtained after the enzymatic treatment (5% pectinase and 5% cellulase) of P. bungeana needle sections clearly showed that the isolated anticlinal cell walls of the foliar endodermis in fact formed a complete network surrounding the vascular tissue. The vascular tissue resisted enzymatic digestion and was enclosed by the cylindrical net of isolated endodermal cell walls. All kinds of micrographs revealed that the isolated Casparian strip were not free from cytoplasmic debris. The mesh size of the net differed in shape and size between each other, which reflected the difference of the morphology of endodermis cell. The enzymatic technique used here may indeed provide sufficient amounts of Casparian strips for detailed analytical investigations.2.The observation on the foliar endodermis by means of light microscope, fluorescence microscope, laser scanning confocal microscope, scanning electron microscope and transmission electron microscope indicated that the radial and transverse walls were visible as fluorescence bands, which occupied the cell wall about 1/2 to 2/3. Furthermore, numerous pit fields became clearly visible in the radial wall of endodermis. One of the most striking features of SEM was its pronounced undulation in thelongitudinal direction. Band plasmolysis, typical to the root Casparian strip, occurred in the foliar endodermis, and plasmodesmata connections across adjacent cell walls presented in the wall under TEM as well. The above evidence further confirmed that the endodermis of P. bungeana needle also possessed Casparian strip, similar to those isolated from roots endodermis.3. The chemical composition of Casparian strips was studied by histochemical method, Fourier transform infrared spectroscopy, ultraviolet spectrum, gas chromatography combined with mass spectrometry. It was concluded that Casparian strips were impregnated with lignin, suberin, cellulose and cell wall proteins. Thereinto, the content of lignin was highest and the main type was guaiacyl lignin.4. Based on the analysis of multiple regression, the development of Casparian strips was significantly correlative with the length of P. bungeana needle, a certain correlative with the occurrence of xylem and the expansion of radial wall of endodermis, and almost had few to do with phloem. The regression equation was:Y=-52252.615+0.351X1-0.02X2-0.28X3+0.912X4In the equation, Y was the length of Casparian strips in the radial wall of needle endodermis. Xh X2, X3 and X* stood for area of xylem, phloem, length of radial wall of endodermis and length of needle, respectively. The multiple correlation coefficient was 0.984 and a-level was 0.01. The result of test on the regression equation suggested the significance of multiple regression and the reliability of regression equation. The partial correlation coefficient between radial length of Casparian strips and length of needle, area of xylem, radial length of endodermal cell, area of phloem were 0.6589, -0.5057, 0.2608 and -0.0208, respectively.5. The result of enzymatic isolation and histochemical identification indicated that Casparian strips occurred in the species of Pinaceae except K. erelyniana of Keteleeria,P. amabilis of Pseudolarix, T. chinensis and T. longibracteata of Tsuga. The histochemical reactions of radial walls of endodermal cell in situ were indicative of lignification in most species of Pinaceae. The extent of difficulty in isolating Casparian strips from endodermal cell...
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