Effect of the short period heating on cold resistant ability of the Asian pear cultivars Chuwhangbae and Niitaka during winter period

The purpose of this study was to investigate responses of pear cultivars Niitaka and Chuwhangbae under short period heating on cold resistance degree of flower buds. Experience was conducted in annual shoots flower bud where used control state (non-heated) and shoots which were artificially heated (AH) during 72 hour in water in room condition (18-20°С). To assay cold resistance of cultivars they were treated under negative temperatures -10°С,-15°С,-20°С and -25°С during 2012-2013 winter period with every 15 days interval and was detected changing of cold resistant depending on the fluctuation of the outside temperature and cultivars own characteristics. A study revealed that during organic rest period before entrance to deep dormancy Chuhwangbae was more resistant to low temperature under control and AH state than that of Niitaka and the damaging level of flower buds slowly decreased and reached minimum by mid January. And by March the damages was increased again. Cold resistant cultivar Chuwhangbae responds more sensitively to external environments. It means that it can realize with high rate hardening process by the restructuring of the plant protoplasts and the transition process to the new metabolic energy level by effecting negative temperatures. And we assume that it might be closely related with dormancy, concentration of the mineral elements, water potential and transition processes of metabolism to the new energetic level.