Responses of chilling resistance to photoperiodic dormancy induction in peach leaf.

Abstract

Taking 6-year-old "Chunjie" peach as test material, and the peach in natural condition as the control, this paper investigated induced effects of long-day and short-day photoperiod on dormancy and responses of chilling resistance to photoperiodic induction during dormancy induction process. The results showed that the trees of long-day and short-day treatments could both enter dormancy induction under the gradually decreasing temperature. The long-day treatment was 1 week later than the control, while the short-day treatment was 1 week earlier. The total water content and free water content both decreased, and the bound water content and the ratio of bound water/total water increased with the development of dormancy. SOD and CAT activities changed as unimodal curve during dormancy induction, and the peak values appeared at the late stage of dormancy induction, POD activity decreased rapidly after the start of dormancy induction, and rebounded to form a small peak at the late stage of dormancy induction. The soluble protein content declined, proline and malonaldehyde (MDA) increased continuously, and the injury rate increased. Long-day could increase SOD and CAT activities and proline content, alleviate the decline of POD activity and soluble protein content, and reduce the growth rate of MDA and injury rate, which indicated leaf damage was lighter in long-day treatment than in the control. However, they changed differently under short-day treatment, especially the leaf injury rate was higher than the control, exhibiting a lower chilling resistance. Prolonging illumination was suggested to improve leaf chilling resistance in practical production if environmental temperature permitted.