Water relations and keeping-quality of cut gerbera flowers. IV. Internal water relations of ageing petal-tissue

Abstract

The relationship between relative water content (R.W.C.) and water potential (ψtotal) of Gerbera petals was studied when cut inflorescences aged in a vase. The regression of sap osmotic potential (ψosm), matric potential (ψm) and pressure potential (ψpress) on R.W.C. appeared to be the same for young and old inflorescences. Computing ψpress as the difference between ψtotal measured with a pressure chamber and ψosm + ψm gave erroneous results for old cut inflorescences because of the increasing leakage of ions from petal cells. As there existed a correlation between ψpress and the bending of petals (B) caused by a small weight, it was possible to obtain time courses of ψpress by measuring B. Time courses of ψosm and ψpress of petals were completely different when inflorescences aged on the plant as compared to ageing in a vase. For inflorescences ageing in a vase without stem plugging, ψosm increased during the first 6 days, followed by a decrease, and ψpress decreased during the entire vase period. When inflorescences were left on the plant, ψosm was steady during the first 6 days and increased thereafter, whereas ψpress was steady until day 6 and then decreased. A hypothesis to explain the difference between inflorescences in the vase and on the plant is given. © 1979.