Development Anatomy Of Vegetative Organs And The Ultrastructural Changes Of Laticifers In Euphorbia Helioscopia L.

Euphorbia helioscopia L. is a biennial herbaceous species in Euphorbia. The whole plant of E. helioscopia has been used as medicinal material for a long history. They are widely distributed in all the provinces besides xinjiang and Tibet. At present, the researches about E. helioscopia were mostly focused on the biology, chemical constituents, pharmacological action and clinical application and so on. But its structure and development of vegetative organs, and ultrastructure changes of laticifers during its development had not been reported. Experimental methods of plant anatomy, histochemistry and transmission electron microscopy were used to investigate the structure and development of vegetative organs, the distribution characteristics of laticifers and the ultrastructural changes of laticifers during its development process in this paper. The results were as follows:1. The developing process of vegetative organs in E. helioscopia is similar to general development laws of herbaceous of dicotyledonous plants. The primary xylem was triarch in the root of E. helioscopia. The secondary growth mainly relied on the activities of vascular cadmium and cork cadmium, and the secondary structure was composed of periderm and secondary vascular tissue. The development of the stems could be divided into four stages: promeristem, primary meristem, primary structure and secondary stage of growth, its primary structure was consists of the epidermis, cortex, vascular bundle ring and pith, and there had some cavities in pith. The activities of vascular cambium of the stems were inactive and only produced a few secondary vascular tissues. Furthermore, the stem had no periderms formed. However, the development of E. helioscopia leaves could be divided into three stages: promeristem, primary meristem and mature structure. The leaf was the typical bifacial one.2. The laticifers in E. helioscopia is non-articulated. In roots, laticifers were mainly distributed around phloem and few were observed in the cortex, and some laticifers may extend into the xylem by apical growth. In the stem, latcifers were mainly distributed in the outside of phloem and cortex close to the phloem. In the leaf, laticifers were mainly distributed in the phloem of the main veins; the mesophyll tissues have also the distribution of laticifers. The diameter of laticifers varied slightly in three organs, whose descending order lists as root, stem and leaf. From the results of PAS reaction, the mature root had not the distribution of starch grains; starch grains scattered in some cells in stems. Lots of starch grains were distributed in the mesophyll tissues in the leaf. There are a large number of starch grains distributed in the embryo and endosperm of E. helioscopia seed, but its size has obvious difference.3. Development of laticifers in E. helioscopia has four main characteristics:(1) In the early stage of laticifers development, the nucleus is about round and evident. The cytoplasm which scattered various organelles and numerous ribosomes is relatively homogenous and electron-density. (2) In the process of development of laticifers, the development of small vesicles is the main features. Vesicles originated from the endoplasmic reticulum, during the development process, they fused each other and also fused with the vacuole, finally a central vacuole was formed in the mature laticifers, which filled with a large number of latex particles. At the same time, the cell wall was gradually thicken, it formed alternate stripes of light and shade in the mature laticifers. (3) The dictysomes were active and secreted lots of vesicles into the cytoplasm during the all process of development. (4) At the end of the differentiation of laticifers, cytoplasm significantly reduced, electronic density was lower. The mitochondria and plastids occured degenerate.