Study On Photosynthetic Characteristics Of Purple Cabbage

The photosynthetic characteristics and pigment content of purple cabbage ('Zaohong'and'Hongri') were researched compared with a common cabbage variety'Zhonggan 11'. The pigment content and light-requiring characteristics of different leaf-position leaves in the initial heading stage effects of shading and temperature on pigment content and photosynthesis of purple cabbage were studied with''zaohong'and'chaozi'as materials. The results showed as follows.1. The two varieties of purple cabbage differ less in pigment content and photosynthetic rate (Pn), their chlorophyll content were higher, the Pn were lower than those of'Zhonggan 11'. There were more proportion of anthocyanin in purple cabbage, but no in cabbage. The Pn of purple cabbage was highest in initial heading stage, and decreased by a less margin in last stage compared with that of cabbage. The chlorophyll content was highest in middle heading stage, but the anthocyanin content increased as growing period getting along. The daily Pn varied in a single peak curve. The light compensation point and light saturation point of'Zaohong'was 68.5μmo1·m-2·s-1, and 1,077.5μmo1·m-2·s-1 respectively, the CO2 compensation point and saturation point was 70.4μmo1·mol-1 and 1,140μmo1·mol-1, which higher than those of'Zhonggan 11'. The Pn of'Zaohong'was highest in 20℃, the compensation point was -4.4℃at low temperature and 51.3℃at high temperature, which lower than those of'Zhonggan 11'.2. The chlorophyll content of upper leaves was lower than that of middle or lower ones, but no significant difference was found between middle and lower leaves. The anthocyanin content of the upper leaves was the highest and the middle was the lowest among three leaf-position leaves. The differences of plenylalanine ammonia lyase (PAL) activity and soluble sugar content among different leaf-position leaves were similar to those of the anthocyanin content. The photosynthetic rate of middle leaves was the highest and upper one was the lowest. The light saturation point of the middle leaves was the highest and the lower leaves were the lowest. The light compensation point of the upper leaves was the highest and the lower leaves were the lowest.3. The anthocyanin and chlorophyll contents, PAL activity and Pn declined remarkably in shading condition, and the higher the shading degree, the larger the debasing extent.4. Under the same PFD condition, no remarkable difference in anthocyanin content between the treatments of HT and MT were found, but that of in LT was higher significantely than those of HT and MT. The chlorophyll content of MT was the highest and the LT was the lowest. The difference of PAL activity in different treatments were consistent with that of anthocyanin content. The soluble sugar content of LT was the highest, MT in the next place, and the HT was the lowest.5. Correlation analysis revealed that there were positive correlation between PAL activity, soluble sugar content and anthocyanin content respectively.