The present studies were conducted to determine the growth and change in endogenous hormones and isoenzyme patterns in the last internode of Tulips gesneriana L. cv. Jacqueline after exogenous growth regulator applications. The physiological mechanisms were of interest to analyze and study as follow:
The activity (Rf 0.6) of all auxin-like substances was increased in the intact, NAA, IBA and GA_(4+7) treatments with which the neck growth was strikingly promoted. The activity of that in gynoecium was particularly outstanding. GA₃, BA, ABA treatments or removal of flower head (flower bud) showed practically no neck growth, indicating that activity of endogenous auxin was decreased. The activity of auxin reduced by either PP333 or TIBA treatment was again increased notably by the combined treatments with NAA. Activity of endgenous cytokinin-like substances was conspicuosly increased in gynoecium itself, and flower head removal, NAA and IBA treatments with which the neck growth was promoted. Activity of GA-like substances was low with both ABA, PP333 treatments, gynoecium and removal of flower head with which the neck growth was inhibited, but it became fairly strong by NAA and IBA treatments.
For isoenzymes, acid phosphatase isoenzymes exhibiting a number of bands which reduced in theatment that the neck growth did not occur, and the endogenous auxin activity was low. Three large numbers of band was found with GA_(4+7) or NAA treatment which promoted neck elongation. The number of bands for esterase isoenzymes was always higher in the intact, GA_(4+7) and NAA treatments, which stimulated neck growth. The number of bands for peroxidase isoenzyme was lessened in gynoecium removed and intact plants, and this normal neck grow th, and activity of endogenous auxin was increased, which the front most migrated bands were more with GA_(4+7) treatment, showing normal neck growth as in the case of NAA treatment, than gynoecium and the intact plant.
The 3rd internode growth were notably inhibited by the removal of flower head or gynoecium, and this was reversed considerably by NAA or IBA treatment, and the activity of auxin-like substances was markedly increased by this treatment. The number of isoenzyme bands for acid phosphatase, esterase and peroxidase was found to be different with NAA or IBA treatments, which caused elongation in the neck growth.
Therefore, it can be suggested that the 3rd internode and neckgrowth are evidently promoted by auxin-like substances or perhaps by other metabolites.
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