棉 花 学 报       Cotton Science     2009，21(5)：427-430

Study on the Spatial Distribution of Leaf N Content and SPAD Value in Cotton
LUO Xin-ning^1，3，CHEN Bing^1，4*，ZHANG Ju-song^2，4，JIANG Ping-an¹，LOU Shan-wei²，PENG Xiao-feng²，HE Jia-lin²
（1.College of Grassland and Environment，Xinjiang Agricultural University, Urumqi,Xinjiang 830052, China; 2. College of Agronomy，Xinjiang Agricultural University, Urumqi, Xinjiang 830052, China; 3.Akesu Professional and Technology College, Akesu, Xinjiang 843000, China; 4.National Cotton Research Center of Ministry of Education, Urumqi, Xinjiang 830052, China）

Abstract：Based on the cotton pot experiment involving four varieties (three were upland cotton and one was sea island cotton) and two N treatments and field experiment with different N treatments,the spatial differences of N and Chlorophyll contents (SPAD value) in the four upper fully expanded leaves and their relationships with whole leaf and plant N concentration were investigated. The results showed that leaf N contents and SPAD values at different leaf positions differed obviously,leaf N contents and SPAD values increased and differences among different position leaves decreased at high N rates. The sensitivity of the fourth leaf from the top to N was the highest,and next was that of the second leaf from the top was the lowest,while that of the first and the third leaves varied within the varieties. The SPAD value of the fourth leaf from the top was most correlated with whole leaf and plant N concentration among the top four leaves through the bud stage,initial-flowering stage. The CV of SPAD value of the fourth leaf from the top was the smallest under optimal N level. It was suggested that the fourth leaf from the top was the most ideal indicator when using SPAD value or leaf color difference to diagnose N status in cotton.
Key words：cotton; nitrogen diagnosis; SPAD value; leaf position; nitrogen content
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