| As one of the important plant hormone, auxin regulates many processes in plant growth and development, but its essential functions in cellular level are still unclear. The model plant Physcomitrella patens has the advantages of simple structures and short developmental cycle. Because the protonemas and gametophore leaves of Physcomitrella patens are consist of monolayer cells, the effect of exogenous auxin to each cell is almost the same, the Physcomitrella patens is ideal for research on the role of auxin in regulating plant development in the cellular level.Studies on the physiological effects of auxin were less in moss. The only report indicated that auxin analogue NAA induced the transition from chloronema to caulonema, and inhibited chloronema from branching. In this study a continuous observation system of Physcomitrella patens protonema was established, in order to explore the effect of auxin on protonema development. Using this system, we found that IAA was different from NAA. IAA could promote the relatively stable chloronema cells into meristematic state, and effects of different concentration of IAA were distinct. In addition, we also studied the development processes of Physcomitrella patens gametophores and protoplasts treated with different concentrations of exogenous IAA. The results showed that the IAA could promote the formation and growth of gametophores, and stimulated the protoplast cell division obviously. Effective concentration of IAA could be very low,and the optimal concentration of IAA on protonemas growth was lower than the gametophores. This study also found that during the growth process of Physcomitrella patens gametophores, the endogenous auxin was polar distributed in the stems of gamephores and always near the base. The auxin signal was also regularly localized in the protonemas, indicating that auxin plays an important role in the development of Physcomitrella patens and the functions are closely related to auxin polar distribution. |
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