Growth and Vegetative Development
Yaroch, Samantha , Flannery, Ellen , Dannenhoffer, Joanne .
ABA inhibits PCD during vascular element differentiation?
Tracheary elements undergo programmed cell death (PCD) during differentiation; whereas, the self-digestion that occurs during sieve element development has been called a cell semi-death (van Bel & Knoblauch, 2000). One of the major obstacles to studying sieve element development is the difficulty in finding elements at different stages of differentiation. The number of sieve elements in vascular bundles is low and the process of differentiation lasts less than 24 hours (Sjolund, 1997). PCD in barley aleurone cells can be inhibited by ABA as detected by DNA fragmentation; this inhibition could be reversed by removal of ABA (Wang et al., 1996). Could ABA also be used to inhibit PCD in xylem elements and is the process that occurs in phloem elements during self-digestion similarly affected? Pumpkin seeds were treated with 4 mM ABA for 3 days in the dark. After 3 days, the average number of mature vascular elements per bundle was counted. There were fewer mature tracheary elements and sieve elements per bundle after ABA treatment compared to a water control (p<0.01). Removal of ABA followed by 2 days incubation with water was compared to 5 days of water treatment to determine if the inhibition of ABA could be released. The number of mature tracheary elements after 5 days was not significantly different than the elements in the control, but the number of sieve elements was significantly higher (p<0.05). ABA inhibited cell differentiation of vascular elements - PCD in the xylem and self-digestion in the phloem - and this inhibition could be reversed. The similar response of tracheary and sieve elements to the ABA hormone suggests the self-digestion or cell semi-death in the phloem shares similar regulation to and may be a modification of PCD.
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1 - Central Michigan University, Biology, 217 Brooks Hall, Mt. Pleasant, MI, 48859, USA
2 - Central Michigan University, Biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM