Year: 2000
Type: article
Abstract: Prohexadione-Ca (BAS 125 W) is a new growth retardant for the inhibition of excessive vegetative growth in apple and other plant species. From work with enzyme preparations, it is known that prohexadione-Ca mimics 2-oxoglutaric acid, the co-substrate of dioxygenases, which catalyze late steps in gibberellin (GA) biosynthesis. As a result, the formation of growth-active GAs is reduced. In order to have a better understanding of its effects in intact plants, we have analyzed the GA status of treated and untreated apple plantlets. In a typical experiment, the following results were obtained: Plants (cv. Jonagold on M9 at 19 cm of new shoot growth) were sprayed until run-off with an aqueous preparation containing 25 ppm of active ingredient. After 22 days of cultivation under greenhouse conditions, total new shoot growth of the controls and the treated plants was 55 cm and 44 cm, respectively. In the apical part of this material the following GAs (roughly ordered in biosynthetic sequence) were detected at the following levels (control/treated in microgram per kilogram dry weight): GA 19 (31/62), GA29 (24/36), GA20 (11/20), GA1 (4/3), and GA 8 (8/3). These results clearly demonstrate that prohexadione-Ca blocks primarily the hydroxylation of GA 20 into GA 1 . This leads to reduced levels of the highly active GA 1 and of GA 8 , its inactive metabolite, whereas GA 20 and the other inactive precursors accumulate. The data support older observations obtained in vitro, which indicate that GA 20 3β-hydroxylase and related dioxygenases are the primary targets of prohexadione-Ca and similar compounds.
Source: HortScience
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $3,000
OpenAlex ID: W1914441366