Effect of Water Stress on Turgor Differences and 14C-Assimilate Movement in Phloem of Ecballium elaterium

Abstract
The effects of water stress on pressure differences and 14C-assimilate translocation in sieve tubes of squirting cucumber E. elaterium A. Rich were studied. Water stress was induced by transfer of plants from culture solution to a polyethylene glycol 6000 solution having an osmotic potential of -18.2 atm. Sieve tube turgor, turgor differences between source and sink and translocation rate were decreased. After 260 min of translocation, only 19% of the total fixed 14CO2 had moved out of the leaf, compared to the control value of 62% after the same period of time. Apparently water stress slows translocation by lowering sieve tube turgor differences, which are essential for the pressure flow mechanism of conduction.