Changes in endogenous abscisic acid levels during dormancy release and maintenance of mature seeds: studies with the Cape Verde Islands ecotype, the dormant model of Arabidopsis thaliana.
Mature seeds of the Cape Verde Islands (Cvi) ecotype of Arabidopsis thaliana (L.) Heynh. show a very marked dormancy. Dormant (D) seeds completely fail to germinate in conditions that are favourable for germination whereas non-dormant (ND) seeds germinate easily. Cvi seed dormancy is alleviated by after-ripening, stratification, and also by nitrate or fluridone treatment. Addition of gibberellins to D seeds does not suppress dormancy efficiently, suggesting that gibberellins are not directly involved in the breaking of dormancy. Dormancy expression of Cvi seeds is strongly dependent on temperature: D seeds do not germinate at warm temperatures (20-27 degrees C) but do so easily at a low temperature (13 degrees C) or when a fluridone treatment is given to D seeds sown at high temperature. To investigate the role of abscisic acid (ABA) in dormancy release and maintenance, we measured the ABA content in both ND and D seeds imbibed using various dormancy-breaking conditions. It was found that dry D seeds contained higher amounts of ABA than dry ND after-ripened seeds. During early imbibition in standard conditions, there was a decrease in ABA content in both seeds, the rate of which was slower in D seeds. Three days after sowing, the ABA content in D seeds increased specifically and then remained at a high level. When imbibed with fluridone, nitrate or stratified, the ABA content of D seeds decreased and reached a level very near to that of ND seeds. In contrast, gibberellic acid (GA3) treatment caused a transient increase in ABA content. When D seeds were sown at low optimal temperature their ABA content also decreased to the level observed in ND seeds. The present study indicates that Cvi D and ND seeds can be easily distinguished by their ability to synthesize ABA following imbibition. Treatments used here to break dormancy reduced the ABA level in imbibed D seeds to the level observed in ND seeds, with the exception of GA3 treatment, which was active in promoting germination only when ABA synthesis was inhibited.
Ali-Rachedi
Sonia
S
UER de Physiologie Végétale, INA-PG, UMR INRA-INAPG Biologie des Semences, 16 rue Claude Bernard, 75231, Paris Cedex 05, France.
Bouinot
Denise
D
Wagner
Marie-Hélène
MH
Bonnet
Magda
M
Sotta
Bruno
B
Grappin
Philippe
P
Jullien
Marc
M
D000040:Abscisic Acid / Q000378:metabolism*; D000354:Africa, Western; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018525:Germination; D005875:Gibberellins / Q000494:pharmacology; D008954:Models, Biological; D009566:Nitrates / Q000494:pharmacology; D011728:Pyridones / Q000494:pharmacology; D012639:Seeds / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013696:Temperature
D005875:Gibberellins; D009566:Nitrates; D011728:Pyridones; C013351:fluridone; D000040:Abscisic Acid