To study the diurnal variations of photosynthesis in leaves of Panax notoginseng.[Method] The experiment was carried out to study the diurnal variations of photosynthesis in leaves of Panax notoginseng under 14％ light transmission rate in the field.[Result] The results indicated that the demand for light in the one-year-old leaves was less than in the two-year-old leaves,and this shown on the curves of the diurnal variations of the net photosynthetic rates in the one-year-old leaves and two-year-old leaves was that the former had one peak and the latter two peaks; The non-stomatal limited elements caused "midday-depression" of the net photosynthetic rates in the one-yearold leaves.The diurnal variations of transpiration rate had the same tendence as the stomatal conductance ; The result of single correlative analysis showd that the dominant factors that influenced the net photosynthetic rates were the internal CO2 concentration,photosynthetically active radiation and the air CO2 concentration,and the influence of the internal CO2 concentration was most significant.[Conclusion] Influencing factors for Panax notoginseng net photosynthetic rate are various.%[目的]对三七的光合日变化进行研究.[方法]在14％的荫棚透光率的田间条件下,测定三七的光合日变化.[结果]1年生三七对光的需求小于2年生三七,表现在净光合速率的日变化上,前者呈“双峰型”曲线,后者成“单峰型”曲线.1年生三七午间光合速率下降是由非气孔因素引起的.蒸腾速率的日变化与气孔导度的趋势基本相同.单相关分析表明,胞间CO2浓度、光合有效辐射及空气CO2浓度均是影响三七净光合速率的主要因子.其中以胞问CO2浓度的影响最为明显.[结论]影响三七叶片净光合速率的因子是多元的.
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