| To clarify the water and nitrogen response mechanisms of high-yield drip irrigated spring wheat to the unstructured carbohydrates(NSC) in different stem and sheath nodes in the Yanqi Basin, a split plot experimental design was adopted, with Xinchun 38(XC38) and Xinchun 45(XC45) as materials, deficit irrigation(W1, 4 500 m3·hm-2) and suitable irrigation(W2, 6 000 m3·hm-2) as the main plots, and N0(0 kg·hm-2), N1(300 kg·hm-2), and N2(400 kg·hm-2) as sub plots, a comparative analysis was conducted on the accumulation and transport of fructose (DP≥4), sucrose, and NSC in the peduncle, top second internode, and other internodes of high-yield drip irrigated spring wheat, as well as their contributions to yield. The results showed that as the growth period progressed, the activities of sucrose phosphate synthase(SPS), sucrose synthase(SS), sucrose glycosyltransferase(SST), fructose content(FC), sucrose content(SC), and NSC content in the stem sheaths of the two varieties at each node all showed an increasing and then decreasing trend, while the activity of fructose hydrolytic enzyme(FEH) showed a decreasing trend. The optimal treatment for SPS, SS activity, and SC was W1N1. The other indicators showed the best performance under W2N1 treatment. Compared with other nodes, the content of fructose and sucrose, as well as their metabolic enzyme activity and NSC content, were the highest in the remaining nodes. The contribution rate of NSC to yield in other internodes was 23.12%-26.42% and 70.43%-85.43% higher than that in the top second and peduncle, respectively. Compared with XC38, XC45 has a higher accumulation and transportation efficiency of storage substances in its stem and sheath, and its NSC contribution rate to yield is 1.36%-24.70% higher. Correlation analysis showed that there is a significantly positive correlation between yield and SPS, SS, FEH, SST activity, as well as SC, FC, NSC; SC is significantly positively correlated with SPS and SS activity, while FC is significantly positively correlated with FEH and SST activity, indicating that the activity of SPS, SS, FEH, and SST affects SC and FC. Path analysis shows that FC, NSC, and SS have the greatest positive effect on yield. For XC38, increasing the activities of FC, NSC, and SS while reducing the activities of SPS and SST can increase yield. For XC45, increasing SS activity, NSC and FC, and reducing SC and SPS activity can increase yield. The interaction between water and nitrogen has a significant impact on the transport rates of NSC before and after flowering, as well as their contribution to yield, and the transportation rates of NSC before and after flowering are greater than those after flowering. Under the conditions of this experiment, the irrigation amount of 6 000 m3·hm-2 and the nitrogen application amount of 300 kg·hm-2 are beneficial for the metabolism of stem and sheath NSC and yield formation of spring wheat under drip irrigation. |