Gibberellins and Kinins

Gibberellic acid and related compounds, referred to genetically as gibberellins, form another class of naturally occurring, plant-growth regulators 

It is now supposed that gibberellic acid stimulates the hormonal production of a-amylase (and, probably, of /9-amylase and others) in the aleurone layer surrounding the endosperm starch-reserve. Gibberellic acid released 400 mg. equivalents of D-glucose per g. in 90 hours in wheat grains, with a maximum hydrolytic activity after 60 hours. The effect on /9-amylase was thought to be a release (to the extent of 85%) from the protein-bound, insoluble form.876 

Photosynthetic activity, measured as uptake of carbon dioxide, depended on the leaf area. Gibberellic acid did not influence photosynthesis per unit 

Gibberellic acid and (2,4-dichlorophenoxy) acetic acid increased the glycoside content of Omithogalum umbellatum, as measured by a biological assay of extracts. The active principle, strophanthidin, is one of the cardiac glycosides. 7 There is little reference in the literature to this type of work, but the hydrolytic effects of gibberellic acid on starch may shift the equilibrium toward phenyl glycoside formation in some plant species. 

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In addition to inhibitory chemicals which enter the plant from the external environment, many endogenous inhibitors appear to function as regulators of seed germination and plant growth and development. The interrelationships between endogenous inhibitors and growth promoters such as the auxins, gibberellins, and kinins remain to be elucidated. 

Recently, the isolation of gibberellin and kinin provided further proof for the coumarin-auxin relation. These substances are included among the plant hormones, although gibberellic acid, a representative of gibberellins, was first isolated as a fungal metabolite, and kinetin, the best known kinin derivative was produced from nucleic acids [119-121]. Both of these compounds, however, were also found in higher plants. 

Seth A, Wareing PF (1964) Interaction between auxins, gibberellins and kinins in hormone-directed transport. Life Sci 3 1483-1486 Seth AK, Davies CR, Wareing PF (1966) Auxin effects on the mobility of kinetin in the plant. Science 151 587-588... 

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