Hormonal control of cell proliferation and xylem differentiation in cultured tissues of XXXX var. Biloxi.

@entity14462 @entity14728 @entity6208 @entity1460
The relationship between tracheary element differentiation, cell proliferation and growth hormones was examined in agar-grown @entity1460 callus. The time course of cell division and tracheary element formation in tissues grown on a medium containing 5 x 10(-7)m @entity6208 and 10(-5)m @entity14728 was determined by means of maceration technique. After a slight lag period, a logarithmic increase in cell number was observed through the twelfth day of the culture period. Cell numbers increased at a considerably slower rate after the twelfth day. The rate of tracheary element formation varied with the rate of cell proliferation. Tracheary elements increased logarithmically during the log phase of growth. As the rate of cell division decreased after the twelfth day of culture, the rate of tracheary element formation also decreased. In the presence of 10(-5)m @entity14728 , cell number increased as the @entity6208 concentration was increased between 10(-9) and 10(-6)m. However, tracheary element formation was not initiated unless the @entity6208 concentration was 5 x 10(-8)m or above. When the Biloxi callus was subcultured repeatedly on media containing 10(-8)m @entity6208 , a tracheary element-free population of cells was obtained. This undifferentiated tissue produced tracheary elements upon transfer to a medium containing 5 x 10(-7)m @entity6208 . In the presence of 5 x 10(-7)m @entity6208 , @entity14728 stimulated cell proliferation between 10(-7) and 10(-5)m, but no tracheary elements were formed without auxin, or with 10(-7)m @entity14728 . Neither @entity14728 nor @entity6208 at any concentration tested stimulated tracheary element formation in the absence of an effective level of the other hormone. However, @entity14462 at 10(-7) or 10(-6)m promoted both cell proliferation and tracheary element differentiation in the absence of an exogenous cytokinin.
