St1udies On Leaf Senescence And¹⁵N-urea Absorption And Utilizationof Apple In Response To Topdressing Nitrogen Application

The effects of leaf senescence and the characteristics of¹⁵N-urea absorption andutilization of fifteen-year-old ‘Fuji’ apple/Malus hupenhensis,two-year-old ‘Fuji’ apple/Malushupenhensis and Malus hupenhensis in response to topdressing nitrogen were explored inPeng lai and Tai’an of Shan Dong province during2010～2011. The main results werefollowed:1、The effects of leaf senescence and the characteristics of absorption and utilization offifteen-year-old ‘Fuji’ apple （Malus robusta Rehd） in response to topdressing nitrogen wereexplored in the study. The results show that the SPAD and activities of SOD, POD and CATare obviously the highest in one-time topdressing application at full-bloom stage, and then intwo-times topdressing application, and the last is the three-time topdressing application. Atthe flower bud differentiation stage, the two-time topdressing application is the highest, andthen the there-times topdressing application, and the lowest is one-time topdressingapplication. At the fruit maturity stage, the three-time topdressing application is obviously thehighest, while the one-time topdressing application is the lowest. At the full-bloom stage andflower bud differentiation stage, the total N contents of leaves of the topdressing nitrogenapplication are not obviously different, while at the fruit maturity stage, the three-timestopdressing application are obviously the highest, and then the two-time topdressingapplication, and the lowest is the one-time topdressing application. The proportions of Nderived from the fertilizer （Ndff） in different organs are significantly different, and the Ndffvalues of the three-time topdressing application are obviously higher than those of the one ortwo-time topdressing. The leaf Ndff value is the highest in the one-time topdressingapplication at the full-bloom stage, the highest value is the two-time topdressing application atthe flower bud differentiation stage, and at fruit maturity stage, the highest value is in thethree-time topdressing application; Plant total nitrogen,¹⁵N uptake and¹⁵N-urea useefficiency are the highest in the three-times topdressing application at the fruit maturity stage.2、The effect on leaf senescence and the characteristics of absorption and utilization of pottedtwo-year-old ‘Fuji’ apple in response to topdressing nitrogen were explored in the study. Theresults show that the plant leaf area、SPAD and the total N content of leaves were obviouslythe highest in one-time topdressing application at full-bloom stage, and the lowest were found in three-time topdressing application. At flower bud differentiation stage, two-timetopdressing application were the highest, and the lowest were in one-time topdressingapplication. At fruit maturity stage, three-time topdressing application were obviously thehighest, while one-time topdressing application were the lowest. The leaf SOD、POD andCAT activity were obviously the highest in one-time topdressing application at full-bloomstage, the lowest were found in three-time topdressing application. At flower buddifferentiation stage, two-time topdressing application were the highest, the lowest were inone-time topdressing application. At fruit maturity stage, three-time topdressing applicationwere obviously the highest, while one-time topdressing application were the lowest; The Ndffvalue in different organs was significantly different and the value of three-time topdressingapplication was obviously higher than that of one or two-time topdressing at fruit maturitystage; Plant total nitrogen,¹⁵N uptake and nitrogen ratio were the highest in three-timetopdressing application fruit maturity stage.3、The effect on leaf senescence and characteristics of absorption and utilization of pottedMalus hupenhensis in response to topdressing nitrogen were explored in the study. The resultswere as follows: Plant height, stem diameter, leaf area and SPAD were obviously the highestin one-time topdressing application at early growth stage, then in two-time topdressingapplication，and the lowest were found in three-time topdressing application. At middlegrowth stage, two-time topdressing application were the highest, and the lowest were inone-time topdressing application. At late growth stage, three-time topdressing applicationwere obviously the highest, while one-time topdressing application were the lowest. The leafSOD、POD and CAT activity were obviously the highest in one-time topdressing applicationat early growth stage, the lowest were found in three-time topdressing application. At middlegrowth stage, two-time topdressing application were the highest, the lowest were in one-timetopdressing application. At late growth stage, three-time topdressing application wereobviously the highest, while one-time topdressing application were the lowest; The Ndff valuein different organs was significantly different and the value of three-time topdressingapplication was obviously higher than that of one or two-time topdressing at late growth stage;Plant total nitrogen,¹⁵N uptake and nitrogen ratio were the highest in three-time topdressingapplication at late growth stage. Three-time topdressing application can not only enhance thetotal N content of leaves, delay leaf senescence, but also can increase the nitrogen efficiency.