Abstract:

Three winter wheat cultivars (Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features were investigated. Daily changes of net photosynthetic rate (Pn), transpiration (Tr) in different growth stages were measured in order to find the relationship between leaf photosynthesis and yield. Instantaneous water use efficiency (WUE) of leaf was calculated from Pn/Tr. It is suggested that relationship between photosynthetic rate and yield changed with the developing stages of wheat. High yield wheat cultivar Jingdong 8（released in the 1990s）had a higher photosynthetic rate (the maximal Pn increased by 77%) and transpiration rate (the maximal Tr increased by 69%), but a lower WUE than the low yield cultivar Yanda 1817 (released in the 1940s) during the day time at stem elongation stage. However, difference of Pn among the three cultivars changed with wheat growth process. Before 10 o'clock Pn in leaves of Jingdong 8 usually was the highest of the three cultivars, but Pn of Yanda 1817 was the highest after 10 o'clock. At doughripe stage, Pn in leaves of Yanda 1817 was the highest among the three cultivars during the whole day. The difference of changing trend of transpiration in three wheat cultivars was similar to Pn, but WUE of Yanda 1817 was the highest in those three cultivars, indicating that the higher yield of Jingdong 8 was achieved via a greater consumption of water. Contrary to the cultivars released in the later period, midday depression of photosynthesis was small in Yanda 1817, which might suggest that Yanda 1817 was resistant to photoinhibition. It is possible that photosynthetic potential in leaves of wheat increased as wheat cultivars was improved over the past six decades. However, it became less resistant to photoinhibition.

不同年代推出的冬小麦品种叶片气体交换日变化的差异
刘合芹^1,2蒋高明^1* 张其德^2* 孙家柱³渠春梅¹郭仁俊³ 高雷明¹ 白克智² 匡廷云²

（1.中国科学院植物研究所植被数量生态实验室，北京100093；
2. 中国科学院植物研究所光合作用基础研究开放实验室，北京10093；
3. 北京市农林科学院作物研究所，北京100098）

摘要：选择 6 0年来北京地区广泛种植的 3个冬小麦 (Triticumaestivum L .)品种 ,在相同的环境条件下种植。为了研究它们的产量与单位叶面积的净光合速率 (P_n)的关系 ,测定了不同生育期P_n、蒸腾速率 (T_r)的日变化 ,并用P_n/T_r计算叶片瞬时的水分利用率 (WUE)。结果表明 :单位叶面积净光合速率与产量之间的关系随生育期不同而变化。在拔节期高产品种“京冬 8号”(九十年代推出 )的光合速率和蒸腾速率在一天中总是最高 ,一天中差异最大时 ,分别比低产品种“燕大 1817”(四十年代推出 )高 77%和 6 9%。而其水分利用率却小于低产品种。这种差异随小麦的生长发育而变化 ,一般上午 10 :0 0前“京冬 8号”的光合速率较高 ,而 10 :0 0后“燕大 1817”的光合速率较高。到腊熟期 ,低产品种“燕大 1817”的光合速率在一天中始终最高。蒸腾速率的变化规律与光合速率相似 ,然而“燕大1817”叶片的水分利用率一般最高。与现代推出的品种不同 ,老品种“燕大 1817”叶片的光合作用午休现象不明显 ,说明它可能具有一定的抗光氧化性。我们认为 ,在品种改良的过程中 ,叶片光合作用的潜力可能有所提高 ,但它的抗光氧化性可能减弱。
关键词： 净光合速率；日变化；冬小麦品种；蒸腾速率；水分利用率

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Key words: net photosynthesis； daily change； wheat cultivars； transpiration rate, water use efficiency