Morphological And Anatomical Studies On Young Stem And Leaf From Cutting Plantlet Of Euphorbia Tirucalli

Euphorbia tirucalli is a species of Euphorbiaceae . It is of multi-usage and multi-function . It has been used as a traditional medicine in Africa and an attractive indoors and landscape ornamental tree in some countries in Southeast Asia . Recently it has become more important and popular as an energy-resource plant of agro-forestry in dry and semi-dry regions .Growing in rather arid zones and mesophytic zones , this species serves as a good living fence post , fire-preventing belts around forests and a good water and soil conservation forest plant. The wood of this species is used for making rafters, toys and veneer. And it is the resource of active charcoal and other industrial raw materials. In foreign countries lots of studies on this species have been made about the chemical compostions of latex and the whole plant, cell suspension culture and energy products . This plant was introduced to some places of China in nineteen seventiies as an ornamental tree . Recently in China studies have been made on this species's cutting and fast propagation ,the induction of cold-resistant mutant and polyploid by Jiang Li juan . But no reports about the systematic study on this species's morphology and anatomy is seen . The author of this paper conducted a systematic researches on the morphology and anatomy of the young stem and leaf from the cutting plantlet, the distribution of laticifers and the development of adventitious root from the cutting plantlet of this species. The main results are as follows :1 The longitudinal section structure of stem tip of Euphorbia tirucalli consists of meristematic zone, elongation zone and maturation zone . The tip has apparent tunica and corpus. Laticifers are distributed in the middle-lower part of meristematic zone , elongation zone and the tcortex of maturation zone. Laticifers stem from meristematic zone .2 The leaf of Euphorbia tirucalli is small . The transverse section structure of leaf blade consists of epidermis , mesophyll and vein . In mesophyll , the spongy tissue cells are absolutely most of it . Spongy tissue cells are arranged closely and small inter-cellular space exists between cells . Very few chloroplasts exist in spongy tissue cells . Palisade tissue is underdeveloped in mesophyll. Few and small veins exist in mesophyll. Vascular tissues in veins are underdeveloped . There are no laticifers distributed in mesophyll tissue . The structure of leaf blade has apparent characters which make this plant control water transpiration , enhance the ability to hold water and adapt to the arid environment.3 The primary structure of stem consists of epidermis , cortex and vascular cylinder .The epidermis sinks to coetex where stomata is formed . No much intercellular space exists in cortex and pith , These structural characters make this plant prevent water from losing from plant body , enhance the function of gases exchange beween environment and plant and adapt to the arid environment. Different sizes and shapes of vascular bundles exist in the stem . Different distances exist between vascular bundles . Lots of laticifers are disturbed in the cortex of stem primary structure .4 The secondary transverse section structure of stem consists of periderm , cortex , vascular cylinder . Phellogen and cambium produce the secondary structure together. Phellogen comes from parenchyma cells close to epidermis . The periderm forms at a later time . So the epidermis , especially the cortex of stem can remain for a very long time .5 Non-articulate laticifers of Euphorbia tirucalli cutting plantlet come from apical meristem of stem tip . Laticifers are distributed in stem tip ., primary structure stem , secondary structure stem . But laticifers are distributed in stem cortex mostly . Many typical laticifers can be observed in longitudinal section structure of stem .6 Young stem of Euphorbia tirucalli produce adventitious roots easily , and adventitious roots originate from the cortex parenchyma cells close to vascular bundles phloems.