Color change and chlorophyll fluorescence kinetics characteristics of Buxus microphylla leaves during the period of overwintering and regreening.

The Royal Horticultural Society Color Chart (RHSCC) and modulated chlorophyll fluorescence analysis technique were used in this paper to study the spatial and temporal color changes as well as chlorophyll fluorescence kinetics curve and parameters of leaves during the period of overwintering and regreening in three Buxus microphylla cultivars：‘Green Beauty’,‘Sunny Side’ and ‘Winter Green’, which have been introduced from abroad to Beijing for more than ten years. The results indicated that sun leaf color of three cultivars of B. microphylla showed different levels of changes during the whole period. The color of ‘Green Beauty’ changed least, while ‘Sunny Side’ and ‘Winter Green’ showed serious discoloration. By contrast, shade leaf color of all cultivars almost presented no changes during the process. In addition, significant differences were observed in the chlorophyll fluorescence kinetics induction curve(FI) and the steadystate multistep fluorescence curve (SMS) from sun and shade leaves of three cultivars during periods of overwintering and regreening, and those differences were cultivars dependent. Before regreenning, sun leaves FI dynamics activity and fluctuations of SMS were significantly lower than those of shade leaves in the same period, and the recovery rate of the former was also slower than the latter during regreening. In winter, sun leaves of ‘Green Beauty’ maintained a certain activity of light and dark reactions and electrons transport rate, while ‘Sunny Side’ and ‘Winter Green’ were almost inactive.