Fourth Seed Yam Is A Plant Morphological And Anatomical And Diosgenin Histochemical Localization Study

Dioscorea plants belongs to Dioscoreaceae,Monocotyledoneae. It is the biggest genera of Dioscoreaceae and most species have important edible and medicinal value. Diosgenin which was abundant in rhizome of Dioscorea can be used to synthesize contraceptive and steroid hormone. About 60% of the products of steroid hormone in the world are synthesized by diosgenin. D.zingiberensis C. H. Wright. and D. nipponica Makino from China are the best raw resource of diosgenin, because of their high content and fine quality. D.composite Hemsl. and D. spiculiflora Hemsl. from Mexico are also important raw resources of diosgenin and there are few researches about them.The morphology, anatomy and histochemical knowledge were used to research and compare this four Dioscorea species, in order to provide some scientific reference for further studies on genus, widen the resource utilizationd and evaluate the germplasm of Dioscorea. The major results are as follows:The plant appearance, leaf and rhizome section features of this four Dioscorea species show obvious difference which can provide some scientific reference in fast identification and distinction of the plants. The type of leaf venation is netted, with 7-11 primary vein and angle of their secondary veins' are different among the 4 species. Areola develops imperfect and square or polygon in shape and most marginal vein ateliosis.The ultrastructure of leaf epidermis cells, epidermis hair and stomatal of 4 Dioscorea species were observed by Environmental scanning electron microscope(ESEM). The results show that leaf epidermis cells of 4 species are irregular or polygon and covered with different shapes of wax layer as flake, crumbs, stripe, particle which are disperse or denseness. There are epidermis hairs both on nervure and mesophyll. The multicellular glandular hairs distributed on all species except D. nipponica. The hair density is more on leaf epidermis than that on secondary veine. The stomatal apparatus is anomacytic type which only distribute on lower epidermis.According the studies on morphology and anatomy, the results indicate that the leaves of the 4 species belong to dorsi-ventral leaf, the upper epidermis is thicker than the lower epidermis and both of them are monolayer cells and have multicellular glandular hairs and nonglandular hairs distribution. There was crystal cell (raphides) in sponge tissue. There are collenchyma and parenchyma distributed in the medial parts of epidermis at the veins. The stem is composed of epidermis, cortex, basic parenchyma and vascular bundle.The cells in outer ground tissue are smaller than cells in inner ground tissue.The collateral and closed vascular bundle of the stems are arranged in two circles,small vascular bundles arranged in outer circle contains 1 or 3 phloem units,big vascular bundles arranged in inner circle contains 2 phloem units and the size and arrangement of the phloem units and xylem vessels have some differences which can be used in further research.The rhizome is built up by periderm, ground tissue and vascular bundle.Only the periderm of D. nipponica is exfoliative. The outer ground tissue contains mucous cells(raphides),starch grains,tannin cells but no vascular bundle. The inner ground tissue occupy widely position,collateral and closed vascular bundle scattering, having bundle sheath.lt has the obvious monocotyledons characteristics of the vascular bundle. D. composite is different from the other 3 species about the distribution of starch grains and vascular bundle.Histochemistry studies of dioscin in 4 Dioscorea species show that the distribution of characteristic colors in the biennial rhizome are the same as in the annual rhizome.But the liquid drops in the biennial rhizome are more big,dark red and has a larger quantity.This shows that the accumulation and the distribution of the dioscin of the biennial rhizome are abundant than that of annual rhizome.The inner ground tissue especially the parts including and aroud vascular bundle are the main synthesis and stock parts of dioscin. The protective tissue and outer ground tissue produce no colors or light red,no distribution or some distribution of dioscin.The different degrees of producing colors show that the dioscin in rhizome is most abundant in D.composite, secondly in D.zingiberensis and D. spiculiflora and the least in D. nipponica.The result of determination of dioscin in 4 Dioscorea species by gravimetric method is the same as this.