Abstract:

Variations of the floret anlage differentiation and mature phenotype of both diploid Robinia pseudoacacia (DRP) and tetraploid Robinia pseudoacacia (TRP) were observed with optic and scan electron microscopes. The differentiation processes and phenotype characters were found as the following. The number and symmetry of bracts, sepals, petals and ovaries of floret were the same in both DRP and TRP with ↑K(5)C5A(9)+1, G (1∶1∶∞), while the dimensions of the all organs in TRP were bigger than those in DRP. The floret anlages differentiated in turn into calyx → petal → stamen → pistil, which had no obvious difference from Papilionaceae plants. Compared with DRP, TRP had bigger epidermis cells in bract, sepal and petal, with more velvet surface, thicker harder longer epidermis hair on their epidermis （except abaxial surface of calyx）, and fatter edge. In TRP, the pollen was chubbier, pollen sac more spatial, stigma plate bigger, stigma more secretion, both filament and style and their epidermis cells longer than DRP. There were remarkable variations in the shape, volume, location and number of bourgeonhole channels and veins on surface of pollen among pollens of TRP. The pollen of TRP was larger than DRP and the shape, character of bourgeonhole channel and veins on surface of pollens of TRP were also different from those of DRP. Based on comprehensive analysis of above variations, the implications of these variations in Genetics and Breeding were discussed.

Key words: Robinia pseudoacacia, tetraploid, flower variation, flower anlage differentiation, phenotype variation