Six spaceflight mutant lines and the control were used as the materials to measure several photosynthetic characteristics of sunflowers by LI-6400 Portable Photosynthesis system at full flowering stage. And photosynthetic characteristics of sunflowers were discussed in relative environmental conditions. The main results showed that photosynthetic rate of some mutant sunflowers were higher than that of the control, but the Pn of the other mutant lines were lower than that of the control. Varieties 1 and 4 had no middy depression phenomenon. Light compensation points (LCP) of the mutant sunflowers were lower and apparent qnautum yield(AQY) higher than that of the control. Some mutant sunflowers have high light compensation points. Therefore, the spaceflight mutant lines were a-ble to use lower-light or higher-light, and thus to accumulate more photosynthetic products at the same time. So the results indicated that the mutants could increase the ability of plants in utilizing wider range of light. The control and mutant sunflowers were clustered into four groups based on Pn and WUE. The results showed that different varieties were obtained by spaceflight mutation. Therefore, sunflowers with higher Pn and higher WUE could be developed and the research can supervise the cultivation of mutant sunflowers in different environmental conditions.%以航天诱变SP6代6个花型变异的向日葵突变株系和对照为材料,利用LI-6400便携式光合测定系统观测盛花期向日葵的光合作用及相关参数,讨论突变向日葵在相应环境条件下的光合特性.结果表明,航天诱变向日葵与对照相比,光合速率有增高和降低型,并出现无“午休”现象的单峰下降型曲线(1号和4号)；突变向日葵光补偿点降低,表观量子效率增加,部分突变植株光饱和点升高,从而使得突变向日葵既能很好地利用强光又具耐阴性,对光的利用幅增宽.利用光合速率和水分利用率对供试向日葵株系进行聚类分析,结果聚为4类,获得光合和水分利用类型十分丰富的向日葵突变植株.
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