© 1997 Heron Publishing—Victoria, Canada
Gas exchange and water relations of Fraxinus americana affected by flurprimidol
Gnanasiri S. Premachandra, William R. Chaney and Harvey A. Holt
Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA / Received August 30, 1995
Summary
Effects of flurprimidol on plant water relations and leaf gas exchange were investigated in one-year-old white ash (Fraxinus americana L.) seedlings subjected to soil water deficits. Flurprimidol (20 mg kg–1 of soil equivalent) was applied to the soil surface of pot-grown seedlings after shoot growth was completed. Two months after
flurprimidol application, water was withheld from one-half of the seedlings. Leaf water relations and gas exchange parameters
were measured 5, 7, 10, 14, 18 and 22 days after withholding water. Under both irrigated and nonirrigated conditions, flurprimidol
treatment resulted in reduced net CO2 assimilation rate and transpirational water loss of seedlings as a result of decreased stomatal conductance. Consequently,
flurprimidol-treated seedlings had higher leaf water potential and relative water content than untreated seedlings. Nonirrigated
flurprimidol-treated seedlings also had greater turgor and sap osmolality and lower osmotic potential at full turgor than
seedlings in the other treatments, indicating that flurprimidol increased osmotic adjustment. Under water-stress conditions,
water use efficiency was lower and gas exchange efficiency was higher in flurprimidol-treated seedlings than in untreated
seedlings, suggesting that flurprimidol treatment enhances survival of plants subjected to soil water deficits.
Keywords:
osmotic adjustment, plant growth regulators, water stress.
