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西藏高原冬小麦旗叶光合速率日变化曲线为平坦或单峰型 ,没有明显“午睡”现象。净光合速率日最高值可与平原接近。光合日总量最高值出现在灌浆中期 ,其值比平原低 4 %～ 34 %。净光合速率达2 0 μmol CO2 .m- 2 .s- 1以上的环境因子组合是光合有效辐射光量子通量密度 2 0 0 0 μmol.m- 2 .s- 1以上 ,气温 2 5～ 2 9℃ ,近地层大气 CO2 密度 0 .4 1 mg.dm- 3以上 ,0 cm地温 1 8～ 2 3℃、5 cm地温 1 5～ 1 9℃。这样的因子组合在高原同时满足的机率不高 ,由于 CO2 浓度与光温因子高值出现时间不同步 ,更由于 CO2 密度比内陆平原低 1 /3,严重制约了光合日总量值 ,高原冬小麦旗叶光合作用的特点是净光合速率日最高值可与平原接近 ,但光合日总量却明显低于平原。
The daily change curve of flag leaf photosynthesis in winter wheat in Tibet plateau is flat or unimodal with no obvious “nap” phenomenon. The highest daily net photosynthetic rate can be close to the plain. The highest total photosynthesis day appeared in the mid-filling, its value lower than the plain 4% to 34%. The combination of environmental factors with net photosynthetic rate up to 20 μmol CO 2 -m-2 .s-1 is the photosynthetically active radiation quantum flux density of 2000 μmol · m -2 · s -1 and the temperature of 25-29 ℃, the atmospheric CO2 density in the near-surface layer is above 0.4 mg · m-3, the temperature at 0 cm is 18 ~ 23 ℃, and the temperature at 5 cm is 15 ~ 19 ℃. The probability of such a combination of factors being met at the same time is not high. Since the CO2 concentration is not synchronized with the high value of the photothermal-temperature factor, and the density of CO2 is 1/3 lower than that of the inland plain, the total amount of photosynthesis is severely restricted. Photosynthetic characteristics of winter wheat flag leaf is the highest net photosynthesis rate with the plain close, but the total photosynthetic day was significantly lower than the plain.