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Photoautotrophic carrot callus was induced by gradually lowering the sucrose concentration in culture medium. In the course of induction, the net photosynthetic rate on chlorophyll basis of callus increased gradually with the decreasing of sucrose concentration in culture medium, and the net photosynthetic rate of photoautotrophic callus could even be higher than that of leaf. In the course of changing into photoautotrophic callus, its chlorophyll content increased gradually, and the dark respiratory rate and the ratio of Chl a/Chl b decreased gradually. Parallel with these was the development of the microstructure of thylakoid of callus.

Microsporogenesis offers an ideal model for studying gene expression, cell division and cell to cell communication during development. The role of auxin in pollen development was investigated in transgenic tobacco plants expressing the coding region of the iaaM gene from Pseudomonas syringae, under control of the promoters Lat-52 (pollen-specific) or TA-29 (tapetum-specific). IAA level in anther of transgenic plants increased significantly, and transgenic plants displayed morphological aberrations not solely attributable to pollen development(such as adventitious root formation on stems, epinastic leaf growth, delayed flowering). These results suggest that expression of Lat-52 and TA-29 are not strictly limited to anther. Anther shape was changed and the number of pollen grains per anther was reduced, but grains could be stained with aceto-carmine. Almost all flowering plants were fertile, although the number of flowers per inflorescence was reduced compared with the wild-type ones. These results suggest that auxin plays an important role in pollen development, and over-expressing auxin synthesis gene could result in aberrant development of pollen.