Wood Anatomy Of Several Mangrove Species Studied

STUDIES ON WOOD ANATOMY OF SOME MANGROVE SPECIESDeng Chuanyuan(School of life science. Xiamen University, Xiamen 361005)Wood anatomical features of 15 mangrove species belonging to Sonneratia, Lumnitzera, Rhizophoraceae including Bruguiera, Ceriops. Kandelia, Rhizophora were surveyed and analyzed. The morphological features of vessels (pores),fibers, rays and axial parenchyma in secondary xylem were described thoroughly by means of optical microscopy, scanning electronic microscopy and laser scanning confocal microscopy. The quantitative features of vessels (pores), fibers, rays in secondary xylem were measured by means of software Lasersharp. These results were used for the identification of species, related to systematic position and correlated with ecological adaptation to intertidal habitats. Variations in the qnantitative wood anatomical features of vessel elements (pores) of R. stylosa, S. caseolaris, B. sexangula, K. candel with different habitats along estuary were studied. Relationship between physicochemical variables in soil and quantitative wood anatomical features were analyzed by means of statistical methods.1. Wood anatomical features of all Sonneratia species native to China were surveyed systematically for the first time. The results showed:A) The specialized wood structures in Sonneratia, which can coordinate conductive capacity with conductive safety, are adaptive to intertidal habitats. These character states include: (1) wide and narrow vessel elements (pores) co-occur; (2) the high pore density and a great percentage of pores in clusters occur; (3) the vesturing and helical structure in Sonneratia improve conductive safety; (4) starch grains in ray cells and septate fibers may have the effect of facilitating conduction by providing a source for sugar transfer into vessels; (5) the wide lumen in fiber is obviously a water storage. 8) Some wood structures are indicative of diagnostic features. S. alba and S. apetala characterized by sclerosed tyloses can be distinct from the other Sonneratia species. Compa/ed to the other Sonneratia species, ray height in S. ovata is significantly higher and ray width is significantly wider. These characters can be used for subsidiary diagnostic features considering that quantitative features in ray are relative to ontogeny.C) Data from wood anatomy supports inclusion of Sonneratia in Lythraceae, which accords with recent results from phylogenetic analysis based on ITS sequences of rDNA. Wood structures relative to main trends in xylem evolution in both Sonneratia and Lagerstroemia showed great similarity except for axial parenchyma types.D) Clustering based on quantitative characters of vessel elements (pores) indicated two clades contain: (\) S. caseoalris and S. caseolaroides\ (2) S. alba, S. ovata, S. apetala and S. hainanensis, which suggests the significance of phytogeny, namely, the Sonneratia species formed into two clades in the course of evolution, one including S. caseoalris and S. caseolaroides by formation of the wider vessel and lower pore131density means high conductive efficiency, the other including S. alba, S. ovata, S. apetala and S. hainanensis by formation of the narrower vessel and higher pore density means high conductive safety.2. The results of comparative wood anatomy between L. littorea and L. racemosa can be used to explain why two species occupy different ecological sites reasonably. Under similar habitats, estimated specific conductance relative to conductive efficiency in L. littorea is 3 times more than that in L. racemosa, which suggests that L. littorea can obtain nutrition and water more readily in the suitable habitats, and thus L. littorea supplant L. racemosa by competition. However, narrower pores and higher pore density occur in L. racemosa, these character states relative to conductive safety are adaptive to saline habitats (water stress), and then can survive more easily under more saline habitats. According to the above description, the difference in wood structure...