Rodrigues, Maria Aurineide , Freschi, Luciano , Purgatto, Eduardo , Kerbauy, Gilberto Barbante .
Effects of abscisic acid and ethylene on competence acquisition for root apical meristem conversion of Catasetum fimbriatum into buds.
Ethylene and abscisic acid (ABA) are known in most plants as signs that exert an inhibitory effect on root growth. Root apices from orchids of the genera Catasetum represent an interesting model for studying signs that regulate root development, since their root apical meristems (RAMs) are able to convert into buds as they age. The aim of this work was to elucidate the effects of ABA and ethylene in regulating C. fimbriatum root growth and RAM competence acquisition to convert into buds. Towards this end, the ethylene emission from 30, 60, 120 and 240-day-old plants of C. fimbriatum was measured, as well as the ABA content from their root tips. In addition, root length and RAM competence to convert into buds were verified in young plants treated with 102, 103 and 104ppm of ethylene during 30 days. The same was undertaken with young root tips treated with 10-3; 10-2 and 10-1ÂµM of ABA. In addition, the ABA levels of root tips isolated from plants previously treated with 103ppm of ethylene were quantified. The results showed that all ethylene treatments caused a decrease of 40% in root length and 100% of RAMs converted into buds. The ABA-treated root tips showed a decrease close to 50% in length, whereas around 70% manifested competence for conversion into buds. Additionally, 240-day-old plants showed the ethylene emission and ABA content about, respectively, five and seven-fold higher than the others, but the treatment of young plants with ethylene was unable to disturb the amount of ABA in the root tips. The present results indicate that competence acquisition of C. fimbriatum RAMs to convert into buds was mediated by higher levels of ethylene and ABA, but ethylene seems to not affect ABA levels during this event. Supported by FAPESP.
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1 - University of São Paulo, Botany Department, Rua do Matão, nº 277 - Cidade Universitária, São Paulo, SP, 05508-900, Brazil
2 - University of São Paulo, Botany Department
3 - University of São Paulo, Experimental Nutrition Department
root apical meristem
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM