[Adaptability of Camellia sasanqua leaf morphology during natural changes in temperature.]

In this study, the adaptability of leaf shape, structure and stomata characteristics of Camellia sasanqua to temperature variation in natural process was investigated by field morphological observation, conventional paraffin section and scanning electron microscopy methods. The results showed that, as the temperature decreased, the leaf color changed from green to dark green, toge-ther with white and purple spots on the leaves. The relative conductivity and the percentage of wi-thered leaves increased initially and then decreased during this period. The highest percentages of relative conductivity and withered leaves in March 2015 were 56.0% and 25.4%, respectively. Different leaf tissue structure indexes, including middle vein thickness, leaf thickness, upper and lower epidermis thickness, upper and lower cuticle thickness, palisade tissue thickness, spongy tissue thickness, ratio of palisade tissue to spongy tissue, cell tense ratio and vein protuberant degree were also determined during the natural temperature change from September 2014 to April 2015. Gradually, these parameters increased initially and then decreased with the decrease of temperature except spongy ratio, which showed the opposite trend. These indicators above changed significantly in different months. Stomata length and width were not significantly changed in October 2014, December 2014 and March 2015, while the percentage of completely closed stomata was higher in March 2015, compared with other months. Taken together, we proposed that the improved adaptability of cold tolerance of C. sasanqua relies on the changes of leaf structure and stomatal closure.