【摘要】 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。更多还原

【Abstract】 Characteristics of canopy photosynthesis in the early heading stage of two Chinese cab-bage cultivars（Lubai No,3 and Lubai No. 8）were studied with the field assimilation cham-ber. The result showed that canopy photosynthetic rate（CPn）of Chinese cabbage was 11.2～14.45 μmolCO₂·m￣（-2） ground·S￣（-1）,or 4.0～4.7 μmolCO₂·m￣2 leaf ·S￣（-1） under normal cul-tivation conditions. There was a little difference between cultivars of a type. But CPnchanged with LAI greatly. Value of μmolCO₂·m￣（-2） ground·S￣（-1）increased and value ofμmolCO₂·m￣（-2） leaf·S￣（-1） decreased with the increase of LAI. Diurnal change of CPn was sin-gle peak curve,peak occuring was at about 11 A.M,CPn of Chinese cabbage decreased to agreat extent under water stress. The volume of the field assimilationm chamber must be suit-able while measuring CPn,It is better to caculate CPn,with ground area.更多还原