The effect of preliminary chilling of broccoli transplants on some antioxidative parameters

The aim of this study was to introduce older transplants of broccoli into field conditions to shorten their growing period and to obtain a crop with a high nutritive value. The additional storage of relatively old (four- and eightweek- old) transplants in a cold chamber before planting in the field shortens the growing period; however, it can influence the chemical composition of the leaves and heads. According to earlier research, the preliminary chilling of transplants affected the high yielding of broccoli; a determination of the quality of plants, including select health-promoting properties, was necessary for their full characteristics. In the present work, the four- and eight-week-old broccoli transplants were kept at 2°C either for one or two weeks before planting in the field. Catalase (CAT) and peroxidase (POD) activity as well and the accumulation of phenolic compounds were determined in the leaves of the transplants before and after chilling. The same parameters were detected in the leaves and heads of broccoli at harvest time. The effect of low temperature treatment on CAT activity was observed only at the stage of transplants; however, the increased activity of POD stimulated by chilling was maintained during the growing period until the harvest. The reaction of the plants to low temperatures can be connected with their mechanism against stress conditions and seems to vary in the case of those antioxidative enzymes. The effect of chilling on the accumulation of phenolics (total, cinnamic acid derivatives, flavonols) was noted only in transplants and was not evident during the harvest. The differences observed between the individual seasons of the experiment, both in enzyme activity and synthesis of phenolics, were most likely caused by the differing climatic conditions