Jasmonates promote abscission in bean petiole expiants: Its relationship to the metabolism of cell wall polysaccharides and cellulase activity

✍ Scribed by J. Ueda; K. Miyamoto; M. Hashimoto

• Publisher: Springer
• Year: 1996
• Tongue: English
• Weight: 577 KB
• Volume: 15
• Category: Article
• ISSN: 0721-7595
• DOI: 10.1007/bf00190583

✦ Synopsis

Jasmonic acid (JA) and its methyl ester (JA-Me) promoted the abscission of bean petiole explants in the dark and light, and the activity of these compounds was almost same. JA and JA-Me did not enhance ethylene production in bean petiole explants in the light, indicating that the abscission-promoting effects of these compounds are not the result of ethylene. Cells in the petiole adjacent to the abscission zone expanded during abscission but not in the pulvinus, and JA-Me promoted cell expansion in the petiole and the pulvinus. JA-Me had no effect on the total amounts of pectic and hemicellulosic polysaccharides in 2-mm segments of the abscission region, which included 1 mm of pulvinus and 1 mm of petiole from the abscission zone. On the other hand, the total amounts of cellulosic polysaccharides in this region were reduced significantly by the addition of JA-Me in the light. JA-Me had no effect on the neutral sugar composition of hemicellulosic polysaccharides during abscission. The decrease in the endogenous levels of UDP-sugars in the petiole adjacent to the abscission zone was accelerated during abscission by the addition of JA-Me in the light. Cellulase activities of pulvinus and petiole in 10-day-old seedlings were enhanced by the addition of JA. These results suggest that the promoting effect of JA or JA-Me on the abscission of bean petiole explants is due to the change of sugar metabolism in the abscission zone, in which the increase in cellulase activity involves the degradation of cell wall polysaccharides.