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In order to determine an easy leaf age(LA)diagnostic method of panicle differentiation stage of sorghum, the panicle differentiation of sorghum and the relationship between differentiation stage and LA and leaf age index(LAI)were investigated. Hybrid cultivar ‘Jinyunuo 3' and conventional cultivar ‘Guojiaohong 1' were used as materials planted in three sowing dates, the panicle differentiation stage and corresponding LA were recorded. The results were as follows:(1)The panicle differentiation could be divided into five stages, i. e. vegetative stage, elongation stage, panicle branch differentiation stage, spikelet and floret differentiation stage, gynoecium and stamen formation stage. The sterile spikelet with stalk could develop to gynoecium and stamen formation stage.(2)With the detention of sowing date, the starting date of panicle differentiation was advanced, and the growth duration shorted, and LA and LAI of each stage of panicle differentiation were decreased, but there were differences among varieties.(3)The relationship between the panicle differentiation stage and LAI conformed to linear regression correlation, with a formula of panicle differentiation stage(Yi)to LAI(Xi) of Yi=bXi+a.(4)With the detention of sowing date, the parameter b and |a| in formula of ‘Jinyunuo 3' were increased, while those of ‘Guojiaohong 1' were decreased. To sum up, it is viable to infer panicle differentiation stage applying LAI, and the results provide theoretical basis for sorghum cultivation index management. [ABSTRACT FROM AUTHOR]