Studies On The Photosynthetic Characteristics Of Several Nonheading Chinese Cabbage Materials

We used diploid and tetraploid of suzhouqing and duanbaigeng, 03Hqiu-001, 03Hqiu-003, 03Hqiu-005, 03Hqiu-006, 03Hqiu-086, 03Hqiu-091, 03Hqiu-131 and 03Hqiu-136 as materials, studied the basic photosynthetic characteristics, photosynthetic physiology differences in different cultivars of non-heading Chinese cabbage, so that we can provide some theory to enhance the production of non-heading Chinese cabbage.1. We studied the diurnal change of net photosynthetic rate(Pn) and its factors of suzhouqing and duanbaigeng in the summer and autumn sunny days. Pn had 'noon sleep' in summer, but not in autumn. The photon flux density, leaf temperature and transpiration rate were the major factors which affected Pn. The effected model of photon flux density and temperature on the Pn in non-heading Chinese cabbage were in the shape of "parabola". The light compensation of non-heading Chinese cabbage was about20-45 μ mol · m^-2 s^-1, the light saturation point was aboutl 100-1300μ mol · m^-2 s^-1. The extreme cold temperature of non-heading Chinese cabbage was aboutl-5℃, the extreme hot temperature was about43 ℃, the suitable temperature was about23 ℃. The order of Pn in different position leaves was middle leaf >outside leaf>inside leaf. The order of the start time of photosynthesis in different position leaves was outside leaf>middle leaD inside leaf.2. Measurement and analysis were made on the net photosynthetic rate, chlorophyll content, chlorophyll a/b, transpiration rate, stomata conductance, intercellular CO₂ concentration, quality and yield in 8 non-heading Chinese cabbage lines. The result indicated that there were differences of net photosynthetic rate, chlorophyll content, transpiration rate, stomata conductance, but there was no difference of intercellular CO₂ concentration and chlorophyll a/b. Soluble sugar, reductive sugar, starch, cellulose, dry materials were close correlated with Pn. Vitamin C, soluble protein, dissociative aminoacids, organic acid had low correlation with Pn. The cultivar that has high photosynthesis efficiency, such as 03Hqiu-091, had high yield level. The yield of non-heading Chinese cabbage was correlated with Pn.3. The diploid and tetraploid of suzhouqing and duanbaigeng were used in this research. Pn of tetraploid was higher than diploid, they different significantly in dubaigeng, but not in suzhouqing. The diurnal change of Pn in tetraploid was similar to diploid. The photon flux density, leaf temperature, transpiration and stomata conductance are the major factors which affected Pn. The photosynthetic pigments content in tetraploid was higher than diploid, they different significantly in suzhouqing, but not in duanbigeng. Chlorophyll a/b had no difference in diploid and tetraploid. Chloroplast in tetraploid was bigger than it in diploid, the grana thickness increased. Yield of tetraploid was more than diploid, but quality of tetraploid had no superiority.