|Author: ||M.N. Westwood|
The balance between auxin and other constituents in plant tissues controls organ formation and is the basis for rooting of excised plant parts.
This balance may be achieved by various combinations of genetic, environmental and chemical factors.
The following facts are important to an understanding of the role of growth regulators in rooting: 1. Budding and rooting are strongly polar, as is the basipetal movement of auxin and rooting cofactors in plants. 2. Nutritional deficiencies usually hinder rooting. 3. Juvenile tissues contain more rooting promotors than adult tissues and lack flower buds which inhibit rooting. 4. Whether bud activity or auxin treatment aids in rooting depends upon 2 and 3 above and the season in which the cuttings are taken. 5. GA and cytokinins tend to inhibit rooting while ethylene, ABA and morphactins may improve rooting.
Such synthetics as SADH, chlormequat and TIBA give variable responses. 6. Both environment and genetic makeup affect the kind and amount or rooting cofactors.
These cofactors appear to be phenolic compounds which interact with auxin to stimulate rooting. 7. Other factors such as stock plant girdling, photoperiod, etiolation, IBA dipping technique, positional effects and maturity of cuttings may affect rooting.
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