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研究结果表明，在正常栽培管理条件下大白菜结球初期的群体光合速率（ＣＰｎ）一般为１１．２～１４．４５μｍｏｌＣＯ＿２·ｍ￣２ｇｒｏｕｎｄ·Ｓ￣（－１），同类型的品种之间差异较小。但结球初期叶面积指数（ＬＡＩ）不同ＣＰｎ差异显著，ＬＡＩ在２～９之间单位时间内单位土地面积上的ＣＰｎ随ＬＡＩ的增加而增加，而单位时间内单位叶面积上的ＣＰｎ则随ＬＡＩ的增加而降低，有利于群体光合作用的适宜ＬＡＩ约为５．５。晴天ＣＰｎ日变化基本呈单峰曲线，峰值出现在上午１１ｈ左右，水分胁迫使ＣＰｎ大幅度下降。研究还表明，测定ＣＰｎ时同化箱的容积要适宜，且以单位时间单位土地面积计算ＣＰｎ为宜。
The results showed that the population photosynthetic rate (CPn) of Chinese cabbage was 11.2 ~ 14.45μmolCO_2 · m ~ 2ground · S ~ (-1) Smaller. However, the leaf area index (LAI) differed significantly among different CPn in the early stage of heading. The LAI per unit area of LAI between 2 and 9 increased with the increase of LAI, while the CPn of unit leaf area per unit time LAI increased and decreased, suitable for population photosynthesis appropriate LAI is about 5.5. The daily variation of CPn in clear day was basically single peak curve, the peak appeared at about 11h in the morning, water stress made CPn decreased significantly. The research also shows that it is appropriate to determine the volume of the assimilation box when measuring CPn, and CPn should be calculated according to the unit of land area per unit time.