我国1950s～1990s推广的玉米品种叶片

自1950s以来，我国玉米（Zea maysL.）产量以年递增幅度为126kg.hm-2.a-1的速率迅速提高。在高肥力自然光照条件下，通过对我国1950s、1970s、1990s等3个年代玉米主要推广品种的光合特性研究表明：当代品种叶片光合速率高且高值持续期长，光合色素叶绿素a、叶绿素b、类胡萝卜素等的含量高且持续时间长，与光合有关的蒸腾速率（E）、细胞间隙CO2浓度（Ci）、气孔导度（gs）等也有较大改良，中下部叶片尤其明显；在生育后期，当代品种具有更高的光合优势。在品种更替过程中光合色素的组成比率没有显著变化，随品种更替生育后期当代品种细胞间隙CO2浓度低的原因不是气孔限制，而是叶片同化CO2能力增强的结果。我国玉米产量的大幅度提高在很大程度上应归功于叶片光合性能的改良。

IMPROVEMENT IN PHOTOSYNTHETIC CHARACTERISTICS AMONG MAIZE VARIETIES IN CHINA FROM THE 1950S TO THE 1990S

Grain yield in China has increased at a linear rate of 126kg.hm-2.a-1 between the 1950s and the 1990s. Comparison of the photo synthetic characteristics of widely planted corn varieties from the 1950s, 1970s and 1990s showed that the net photosynthetic rate (Pn) of modern maize varieties was higher and the high Pn value has continued for a relatively long period. Also over this period photosynthetic pigment (Chl a, Chl b and car otenoids) content and other physiological variables related to photosynthesis ha ve ameliorated signifi cantly. These variables include: transpiration rate (E), intercellular space CO2 concentration (Ci) and stoma resistance (gs). Differences bet ween middle and basal leaves have also become much more distinct. Modern corn varieties had stro nger photosynthesis at growth anaphase than older varieties. As photosynthetic p igment composition and stomatic resistance have not evidently improved, the higher Ci of modern corn varieties probably accounts for higher CO2 assimila tion in the leaves of modern varieties.