Influence Of Nitrogen,potassium And Calcium Fertilization On Nutritional Characteristics And Physiological Mechanism Of Peduncle Cracking Of Pineapple(Ananas Comosus L.cv.Tainong No.17)

Peduncle cracking usually occurs in the production of Tainong No.17 pineapple,which may relate to weather condition,nutrient status,culture technology,and cultivar character.Based on former research,calcium(Ca)nutrition has an big impact on peduncle cracking,and in practice application of nitrogen(N),potassium(K)and Ca fertilizers can influence plant Ca nutrition.In the present study,different fertilization treatments were set up in a field experiment,i.e.CK(conventional fertilization without Ca application),T1(conventional fertilization with Ca application),T2(T1 with high N application),T3(T1with high K application),and T4(T1 with high N and K application),and plant growth responses,nutrient status,peduncle cracking rate under natural flowering condition,and physiological characteristics of cracked and normal peduncle were measured for Tainong No.17 pineapple under each treatment.The main results were as follows:(1)Different fertilization treatments had few impacts on soil nutrient supply,but significantly influenced plant growth.Compared with CK,T1-T4 treatments increased leaf numbers and plant dry weight,with the highest increase occurring in T4.Proportion of dry matter mass distributed in different organs varied with growth stage under different fertilization treatment,with organs in the order of leaf>stem>fruit>peduncle and bud>root.The natural flowering rates were 50%-60% under all the treatments without significant difference whereas the final yields were much higher in T1,T2 and T4 treatment compared to CK and T3.(2)At the fast-growth stage and small-fruit stage,nutrient content in different organs displayed in the order of K>N>Ca.Compared with CK,T1-T4 treatments mainly increased Ca content in leaf,stem and peduncle as well as Cu and B contents in peduncle.Compared with T1,T2 and T4 with high N application showed a tendency of increasing N content in leaf while T3 and T4 with high K application did not affect plant K content.At the small-fruit stage,compared to CK,T1-T4 decreased the ratios of N/Ca and K/Ca whereas T1,T2 and T4 increased the ratios of Ca/Cu and Ca/B in the peduncle.(3)Under natural flowering condition,CK had the highest peduncle cracking rate(7.37%),and T1-T4 significantly reduced peduncle cracking rate(2.08%-3.38%)without difference between the four treatments.The peduncle cracking rate showed no clear correlation with soil nutrient supply,but significantly negatively correlated with peduncle Cu content and significantly positively correlated with peduncle N/Ca ratio at the small-fruit stage.(4)At the small-fruit stage,cracked and normal peduncles displayed varied physiological and biochemical responses under different treatments.Compared with the normal peduncle,cracked peduncle had increased content of water-soluble Ca while compared to CK,T1-T4 showed reduced content of water-soluble Ca in both cracked and normal peduncles.A significantly positive relationship was found between peduncle cracking rate and peduncle pectinesterase activity.Compared with CK,T1-T4 decreased pectinesterase activity but increased cellulose content in peduncle.In conclusion,under the present field condition of this study,when soil Ca level was low,application of Ca fertilizer could significantly reduce peduncle cracking rate of Tainong No.17 pineapple,and increasing N and K application based on Ca fertilization would not increase peduncle cracking rate.