Developmental and Structural Section
Landrum, Vic .
Testing the water-stress hypothesis for wide-band tracheids in two morphological variants of the southern African succulent Anacampseros (Portulacaceae)..
Wide-band tracheids (WBTs) are novel tracheids found in xylary and non-xylary tissues of leaves and stems of species in the South African genus Anacampseros (Portulacaceae), and have a characteristic wide secondary wall that intrudes into the cell lumen. Wide-band tracheids are able to collapse physically under dehydration and rehydrate without loss of function; thus, WBTs are hypothesized to have evolved as a response to water stress conditions. To test this hypothesis, water stress experiments were performed to see effects on WBT formation and development in seed-grown tissues of two morphs, Anacampseros rufescens, and A. ustulata. Tissues were harvested and processed at 30 and 60 days growth, and four cell traits (diameter, lumen diameter, wide-band thickness, and percent cell area occupied by the secondary wall) as well as number of wide-band tracheids were measured. Results show that water stress did affect the expression of WBTs in the broader-leaved A. rufescens, but not in the small-leaved A. ustulata. Water-stressed plants showed a statistically significant increase in wide-band area within A. rufescens; in WBT number, there was an increase of 2000% in the water stressed seedlings of A. rufescens (from Control to 15ml groups). Additional experiments showed that neither nutritional nor temperature stress affected WBT number/structure. Thus, WBT numbers increase in response to water stress. However, other experiments have shown that light intensity exposure also has an effect on WBT traits.
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1 - Washburn University, Biology, 1700 SW College Ave., Topeka, Kansas, 66621, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM