Roper, Becky .
Does water deficit cause a switch from sink to potential source of soluble carbohydrate by xylem parenchyma cells in cotton?
The aim of this study is to determine whether water deficit will stimulate a shift from starch accumulation to soluble sugar accumulation in xylem parenchyma cells of cotton stem. It is hypothesized that extractable enzyme activities associated with starch synthesis (ADP-glucose pyrophosphorylase [AGPase] and sucrose synthase [SucSyn]) would be negatively affected and activities of enzymes of starch mobilization and sugar synthesis positively affected by water deficit, providing a mechanism for osmotic adjustment or for carbohydrate supply to flowers/fruits. However, if the drought is too severe, then when re-watering occurs, enzyme activity will not be able to reach the same levels as pre-drought conditions. Preliminary experiments showed that water deficit has the greatest effect on soluble sugar content in xylem during the flowering stage of two cotton genotypes: Gossypium hirsutum cv. coker-312 and G. hirsutum overproducing spinach sucrose phosphate synthase (SPS). Overproduction of SPS is expected to enhance the response with respect to sucrose synthesis during drought. Activities of SPS, AGPase, SucSyn and amylase from xylem tissue samples were determined and compared with the contents of hexose, sucrose, and starch after leaf, pre-dawn water potentials reached ~-2.0 MPa and after 4 d of re-watering. During drought, SucSyn activity fell, suggesting that sink strength decreased, whereas SPS activity increased. No substantial recovery occurred during rewatering. Sucrose and hexose content increased, being available for osmotic adjustment or for export to flowers/fruits.
Log in to add this item to your schedule
1 - Texas Tech University, Biological Sciences, PO Box 43131, Lubbock, Texas, 79409-3131, United States
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM