Metabolic corollaries of gibberellin-stimulated growth.
thesisposted on 19.11.2015, 09:11 by Stephen C. Fry
Suspension cultures of several species of higher plants were tested for growth-responses to gibberellic acid (GA3). Conditions were defined under which cultures of Spinacia oleracea L. (spinach) and Rosa sp. ("Paul's Scarlet" rose) were promoted in growth (irreversible cell expansion) by 10-11 - 10-6 M GA3. In the Spinacia culture GA3 also (1) promoted the accumulation in the medium of several unidentified low molecular weight phenolic compounds, (2) decreased the level of cell wall polymer-esterified ferulic acid, (3) inhibited the secretion into the medium of peroxidase activity, (4) stimulated the secretion of a strongly acidic pectinic acid, (5) suppressed the accumulation of chlorophyll and (6) apparently promoted the transcriptional activity of the nuclei. Total dry weight accumulation and cell division were little affected. The Rosa culture also responded to GA3 by secreting a low molecular weight phenolic compound and a material similar to pectinic acid. Dry weight accumulation was little affected, cell division was often somewhat inhibited and cell elongation (as opposed to isodiametric expansion) was favoured during GA3-stimulated growth. A hypothesis is advanced for the hormonal regulation of growth in which the peroxidase-catalysed oxidation of cell wall phenolic compounds plays a crucial inhibitory ro1e.