| In this study, FX01 and SC124 which are similar on genetic relationship as research material, set six different nitrogen application levels (0,18,36,72,108, 144 kg N/ha) to study the effect of different fertilizer-N application rate on source-sink characteristics of cassava and provide theoretical basis for efficient utilization of nitrogen fertilizer in the high yield cultivation of cassava. Results are the following:1. Different cultivar and nitrogen application level have significant effects on the sink of cassava. The sink capacity of FX01 was bigger than that of SC124. The sink capacity increased firstly with the increasing amount of nitrogen application and then dropped. The relationship between nitrogen application amount and sink capacity was simulated by a bivariate binomial equation. Through this equation, when N application level of SC124 was 72 kg/ha, the maximum of sink capacity reached 681.2 g/plant. When nitrogen application level of FX01 was 75 kg/ha, the maximum of sink capacity reached 851.9 g/plant. Under the proper N application, the sink capacity increased by the increasing of tuber root number, root length and diameter. While less nitrogen or excessive N application could inhibit root tuber number and root tuber diameter, finally decreased sink capacity.2. N application has significant influence on the establishment of source-sink relationship (SSR) at early growth stage and keeping balance at middle and late growth stage. The proper N application was favorable for promoting photosynthesis and reaching a balance stage of source-sink relationship in advance. At later stage, less or excessive amount of nitrogen application could destroy source-sink relationship balance, which resulted in final production declined.3. At the stages of root tuber formation and root tuber enlargement, proper nitrogen application increased the levels of leaf sucrose and root tuber phloem sucrose, enhanced starch synthesis at the phloem and xylem of root tuber, which may lead to the increase of sink capacity. Less or excessive nitrogen application level could decrease the content of leaf sucrose and phloem sucrose of root tuber, inhibit starch synthesis in the phloem and xylem of root tuber, which resulted in the reduction of sink capacity. At mature stage, the effect of source on sink was less, starch synthesis in root tuber mainly depended on sucrose that produce at early period. |
