Keywords: 
• 小麦 /
• 叶面积 /
• 叶绿素相对质量分数 /
• 根 /
• 产量

Abstract: In order to clarify the relationship between photosynthetic properties of the top‐two leaf and wheat yields under high altitude ecological conditions and a theoretical basis for high yield of wheat cultiva ‐tion and production breeding ,differences of area and chlorophyll S PA D value of the top‐two leaf and root traits and relationships between chlorophyll S PA D value of the top‐two leaf and grain yield among a total of 5 leading wheat cultivars of Yunnan province were studied among 2013 and 2014 in Lijiang ,Yunnan . The results showed that area of the top‐two leaf at flowering ,chlorophyll S PA D value of the top‐two leaf at flowering and maturity and secondary root traits (the number of roots ,root length and weight of dry root) had significant difference among the different types of wheat cultivars .It was observed that the cor‐relations between area of the 2nd leaf from top and the top‐two leaf and grain yield were significantly posi‐tive ,but the correlations between area of flag leaf and grain yield were not significantly positive .The cor‐relations between chlorophyll S PA D values of flag leaf ,the 2nd leaf from top and the top‐two leaf at ma‐turity and grain yield were significantly or very significantly positive ,respectively .The correlations be‐tween the product of area and S PA D value of flag leaf and the 2nd leaf from top at flowering and maturity and grain yield were significantly or very significantly positive ,respectively .In addition ,wheat cultivars (as Yunmai53) that coordinated between developed secondary roots and relatively large area and high chlo ‐rophyll S PA D value of the top‐two leaf at late growing stage had a greater yield potential under high alti‐tude ecological conditions .