No abstract

This paper describes the process of the formation of adventitious roots . There appears to be good agreement that this consists of four stages, dedifferentiation coupled with the formation of a meristematic locus, cell division to form a radially symmetrical cluster of cells, further divisions coupled with organisation into a bilaterally symmetrical meristem and finally growth of cells in the basal part of the meristem which causes its protursion through the epidermis. Evidence for the involvement of auxins in these various stages is reviewed and the extent to which rooting of easy-and hard-to-root species can be accounted for in terms of auxin content discussed. Peaks of IAA occur soon after excision of cuttings in some species and there is some evidence suggesting that this is correlated with changes in peroxidase activity . The possible involvement of cytokinins with auxins is briefly considered.

To ensure minimal disruption and distortion of the root filling and to prevent shredding of the gutta-percha interface, care should be taken to ensure that the final pass of the bur across the root canal is in the correct direction in relation to its direction of rotation.

Cuttings of Cotinus coggyria cv Royal Purple rooted well in the spring but not at all later in the season . Levels of free and conjugated IAA and ABA were measured in cuttings taken at different times of the year. Hormones were measured in the leaf, the upper stem and the lower stem (rooting zone) . In cuttings taken in early June the level of IAA was much higher than that of conjugated IAA . In late July the opposite was found . No significant differences in ABA levels were found although the ABA/IAA ratio changed dramatically.

The effects of 13 growth retardants and inhibitors on the growth of container-grown seedlings of Pinuscontorta var. latifolia Engelm. and Piceaglauca (Moench) Voss were examined. Shoot and root growth was reduced to different extents by the various compounds, thus causing alterations in shoot/root ratios. The results are discussed with regard to the potential use of these chemicals for enhancing survival after outplanting or for use in held-over material. Ancymidol, Ethrel, Phosphon and Maintain caused decreases in the shoot/root ratio and may have potential for use in material to be planted out. CCC, RH531, Ethrel, and Mefluidide appear to have potential for use in held-over material.