A Study on the Recovery Following Freeze–Thaw Injury in Onion and Chrysanthemum

Abstract

Onion (Allium cepa L. cv Sweet Sandwich) and Chrysanthemum (Dendranthema grandiflora `Sunny Denise') tissues were used to investigate protein changes associated with recovery from freeze–thaw injury. Medium-sized onions were slowly frozen to either –4 or –9 °C, subsequently thawed, and divided in two halves. One half was used immediately for ion leakage (IL) measurements and total and microsomal protein extraction, whereas the other half was allowed to recover at 6 to 8 °C in the dark for 4 to 5 days. Chrysanthemum leaves were frozen to –3.75 °C, and allowed to recover first at 6 to 8 °C in the dark (1 d) and then under 12-h photoperiod at 18 °C (3–4 d). Results indicate a 1.4- and 2.5-fold higher IL, compared to control, from onion tissues frozen to –4 or –9 °C, respectively. IL in –4 °C-treated tissues was the same as respective control following recovery; however, it was further enhanced to 3.6-fold in –9 °C-treated samples. Chrysanthemum leaf tissue exhibited a 1.6-fold increase in ion leakage following injury, but completely recovered to control levels after 4 to 5 d. SDS-PAGE profiles revealed an absence of a 25-kDa microsomal protein in the injured onion tissues but, its up regulation during recovery only in reversibly injured tissues. Data also indicated an accumulation of 36-kDa soluble protein in chrysanthemum leaf tissues during recovery. Experiments are underway to further characterize these protein changes.