Antioxidant Enzyme and Compound Responses to Chilling Stress and their Combining Abilities in Differentially Sensitive Maize Hybrids
- D. Mark Hodges *,
- Christopher J. Andrews,
- Douglas A. Johnson and
- Robert I. Hamilton
Dep. of Chemistry, Univ. of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4 Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Central Experimental Farm, Ottawa, Ontario, Canada, K1A OC6 Dep. of Biology, Univ. of Ottawa, 30 Marie Curie, P.O. Box 450, STN A, Ottawa, Ontario, Canada, K1N 6N5 Abstract
Chilling sensitive species often have lower antioxidant capacities than do tolerant species. This study was conducted to determine if antioxidant capacities and carbohydrate concentrations would be useful in a proposed screening technique for chilling sensitivity in maize (Zea mays L.). Leaves of 12 maize hybrids exhibiting differential sensitivity to chilling were harvested at the third-leaf stage under either (i) a constant 25°C control regime or (ii) the control regime plus a short-term chilling shock of 11°C for 1 d prior to harvesting. Catalase (CAT; EC 22.214.171.124), monodehydroascorbate reductase (MDHAR; EC 126.96.36.199), and ascorbate peroxidase (ASPX; EC 188.8.131.52) activities were assessed. Carbohydrate levels were determined as general metabolic indicators of chilling stress. The chill/control ratios of CAT, MDHAR, and ASPX were lowest and concentrations of carbohydrates highest in the most chilling sensitive hybrids. Differences between hybrids in antioxidant capacities to detoxify toxic oxygen compounds may be important in differential chilling sensitivity. The higher chili/control ratios of carbohydrates in the sensitive hybrids after chilling indicated that their rate of assimilate utilization was reduced by the chilling treatment more so than those of the chilling tolerant hybrids. Activities of CAT, MDHAR, and ASPX and concentrations of carbohydrates would thus make excellent indicators of chilling stress in a screening technique for chilling sensitivity of maize.
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