| Abstract: | The effect of water stress on the respiration of the immaturefloral apex of wheat was studied in a controlled environmentand related to changes in water relations, growth, protein synthesis,and solute accumulation. Apex respiration measured in vitropolarographically showed no wounding response and was cyanide-and malonate-sensitive. It decreased with each decrease in apexwater potential  a reaching 40% of the non-stress control rateat –5·0 MPa, irrespective of whether the waterstress was induced by droughting in vivo or non-permeating osmoticain vitro. Apex respiration was not quantitatively related toturgor potential. During drought stress there was a conservation of ethanol-insolubledry matter and water in the apex while ethanol-soluble carbohydratesand amino acids accumulated. The calculated daily import ofsoluble carbohydrate into the apex during the whole droughtstress period remained nearly constant despite falling waterpotential. Respiration of the apex during a drought period wasnot limited by the suistrate supply within the apex. |
