Effects Of Auxins And Cytokinin On Arabidopsis Priamary Root Cell Division And Elongation

From the angle of cell biology, the organ and organization development of all organisms can be divided into two basic process which inclued cell division and cell growth. Therefore, the mechanism of regulating cell division and cell growth has been a fascinating research fields in biology. In the plant kingdom, as a mode plant, the morphology structure of Aarabidopisis thaliana priamary root is relatively simple and can be divided into the meristematic zone, elongation zone and mature zones. Unlike other organs, cell division, elongation (growth) and differentiation were occured in different districts, which provide an ideal material for studying cell division, elongation and differentiation. Plant hormones,in particular,auxin and cytokinin are involved in regulating cell division, elongation and differentiation. Although there are some studies about the mechanism of auxin regulation of cell division, elongation and differentiation, it also need further study.To further investigate the mechanism how auxin control cell division and elongation, we use the primary root of Arabidopsis thaliana as experimental material. By applying different concentrations of exogenous IAA, NAA,2,4-D, we analysis and comparison the primary root length and changes of each parti-tion in various treatments,while applying exogenous auxin can inhibit the grow-th of Arabidopsis primary root, the inhibitory effect of auxin on the primary root can be divided into two categories:IAA, NAA mainly affects the cell elongation of elongationzone, and 2,4-D major affects the ability to divide of meristem zone. Furthermore,comparing with 6-benzylaminopurine(6-BA) on the inhibitory effect of the primary root, the effect of 2,4-D is similar to 6-BA. We analysis the expression genes of auxin and cytokinin signaling pathway using Realtime-PCR, and found the expression of auxin polar transport carrier genes PIN1,PIN3, PIN7, AUX1 were upregulated by IAA and NAA, but reduced by 2,4-D and 6-BA; while A-type ARRs family members of cytokinin signaling pathway were downregulated by the IAA and NAA, and upregulated by 2,4-D and 6-BA. These results show that by applying exogenous IAA,NAA,2,4-D and 6-BA,the growth of primary root was inhibitied and the mechanisms of regulation was different. Based on their effects on cell division, elongation, Auxins and cytokinin can be divided into two classes:IAA and NAA may act on elongation zone inhibiting root growth primarily through regulating cell elongation; 2,4-D and 6-BA inhibit root growth by regulating meristematic zone cell division. This process may be through regulating the expression of polar auxin transport carrier or A-type ARRs.These findings deepen our understanding of the interaction between plant hormones, through the relationship between cell division,cell enlongtion and root length will help us to explain the differences of different organ size and body size.