Changes in antioxidant enzyme activities during cold-acclimation in sweet cherry cultivars grafted on different rootstocks

Abstract

Plant acclimation to environmental stress is governed by several mechanisms including alterations in antioxidant defense systems. The purpose of this study was to investigate the effects of Gisela 5 and Mazzard rootstocks on the cold-hardiness of the sweet cherry cultivars (cvs.) 0900 Ziraat and Lambert, as well as to analyze the changes in activities of antioxidative enzymes including catalase (CAT; EC 1.11.1.6), soluble peroxidase (S-PRX; EC 1.11.1.7), cell wall-bound peroxidase (CWB-PRX; EC 1.11.1.7) and glutathione reductase (GR; EC 1.6.4.2) in cold-acclimated (CA) and non-acclimated (NA) stages. One-year shoots of 4 years-old sweet cherry tree cvs. 0900 Ziraat and Lambert grafted either on Gisela 5 or Mazzard rootstock were collected in CA (in January) or NA (in July) stage and subjected to artificial low temperature tests (4 degrees C, -5 degrees C, -15 degrees C and -25 degrees C) in order to determine the degree of cell membrane injury in bark tissues by ion leakage method. Antioxidant enzyme activities were assayed in another set of samples that were not subjected to low temperature treatments. Our data showed that ion leakage in bark tissues was greater in NA stage compared to CA stage. Ion leakage was below 50% in barks exposed to 4 degrees C and -5 degrees C in either period and above 50% in those exposed to -15 degrees C and -25 degrees C in NA stage. Ion leakage was lower if cultivars were grafted on Mazzard compared with grafting on Gisela 5. In addition, activities in both cultivars of CAT, as well as S-PRX and S-PRX, but not GR, were significantly higher during CA stage compared with those in NA stage. Elevations in CAT and PRX (both cell wall and soluble) activities were more prominent if the cultivars were grafted on Mazzard rootstock. We conclude that, cold hardiness in the sweet cherry involves changes in certain antioxidant enzyme activities depending usually on whether the plant is in CA or NA stage. Our finding that activities of CAT, as well as S-PRX and CWB-PRX in cultivars grafted on Mazzard were higher than those in cultivars grafted on Gisela 5 suggests that cold hardiness may be affected by the rootstock.