Abstract
Phalaenopsis amabilis is important in the Taiwan flower industry. During transportation to international markets, especial the temperate area, chilling may damage plants and reduces their values. The goal of this study is to examine the physiological responses to cold of orchids using the TS97 and K51206. Orchids were exposed to 4°C at different time intervals to examine physiological changes. TS97 was found to be more cold tolerant than K51206 as their better maintenance of membrane integrity at 4°C measured with electrolyte leakage. The photosynthetic capacity of TS97 measured as Fv/Fm was also detected to be greater than that of K51206 at 4°C. Moreover, PaCBF coding for a putative CBF transcription was cloned and the mRNA levels were characterized under cold, drought, salinity, osmoticant and ABA treatments. In TS97, the PaCBF mRNA level was significantly induced within 1 hr after exposure to 4°C, and then accumulated to the highest amount at 10 hr of cold stress. The induction of the PaCBF mRNA level was found to be higher in the TS97 than the K51206. The mRNA level of a putative downstream gene of PaCBF, the PaDhn, was found to follow the increase of the PaCBF mRNA level. Our results suggest that PaCBF mRNA level may be used as a marker of cold tolerance in orchid.