| Variety improvement is an important way in crop yield enhancement, and wheat grain yield obviously increased during cultivar succession. Grain yield is closely related to dry matter & nitrogen accumulation and translocation capacity. Elucidating the evolution characteristics of dry matter & nitrogen accumulation and translocation in vegetative organs of wheat cultivars from different eras would be favor of proving the mechanism of yield enhancement and guiding cultivar breeding and cultural management for high yield, high quality and high benefit production. Pot experiment was conducted during 2006-2007 at Nanjing Agricultural University using seven wheat cultivars from 1950s to 1990s including Wangshuibai (the 1950s), Jiangdongmen (the 1960s), Wan7107 (the 1970s), and Yumai18, Yumai34, YangMai158, NingMai13 (the 1990s) to investigate spatial differences of dry matter & nitrogen accumulation and translocation in vegetative organs and its relationships with grain yield. The main results were as follows:1. The differences of grain yield in wheat cultivars from different eras and the relationships with dry matter & nitrogen accumulation and translocation. The results showed that grain yield significantly increased with cultivar improving process, kernel weight was an important reason. Furthermore, post-anthesis assimilates accumulation (PAA), Post-anthesis nitrogen assimilation(PNA) and contribution of them to grain(CPA and CPN) increased significantly for wheat cultivars in 1990s as compared with other early cultivars, but the contribution of pre-anthesis assimilate and translocation amount of nitrogen accumulation (CTA and CTN) decreased significantly for wheat cultivars in 1990s. The correlation analysis showed that grain yield and accumulation and translocation of dry matter and nitrogen was closely related in cultivar improving process. The grain yield was significantly positively correlated with TAA, PAA, PNA, CPA and CPN, significantly negatively correlated with CTA and CTN.2. The evolution characteristics of the difference of post-anthesis accumulation and translocation of dry matter in vegetative parts were investigated. The results showed that for different vegetative parts, the post-anthesis assimilates accumulation, translocation amount of pre-anthesis stored assimilate and their contribution to grain yield in stems was higher than those in leaves. Especially, the contribution of stored assimilate to grain yield in the basal internodes was increased, but the upper organs maintained a high accumulation and lower contribution to grain yield. Improving translocation capacity of pre-anthesis stored assimilate in upper organs base on higher post-anthesis assimilate accumulation would be an important way to further enhance wheat yield.3. The evolution characteristics of nitrogen accumulation and translocation in difference spatial vegetative parts were investigated. The results showed that total nitrogen accumulation and ratio to total nitrogen at anthesis in early cultivars were remarkable higher than those in recent cultivars. However, capacity of post-anthesis nitrogen accumulation of wheat cultivars in 1990s enhanced. For different vegetative parts, nitrogen translocation amount, nitrogen translocation efficiency, and the contribution to grain in leaves was higher than those in stems. Nitrogen translocation amount, nitrogen translocation efficiency in stems and leaves of wheat cultivars in 1990s was improved, but contribution of nitrogen assimilates accumulation in leaves decreased. For different spatial levels, nitrogen translocation amount and efficiency in the upper organs was modified, the lower parts of stems and leaves showed a contrary tendency. Leaves dependence of grain nitrogen accumulation weakened in the improving process. Improving post-anthesis nitrogen accumulation, as well as translocation capacity of upper organs would be an important way to further enhance grain nitrogen accumulation.4. Differences of flag leaf photosynthetic and senescence characteristics and key enzymes activities of nitrogen metabolism in different eras were investigated. The results showed that in the improving process flag leaf SPAD value, soluble protein content, GS and GPT activity were enhanced. In late filling the photosynthetic rate (Pn), maximum photochemical efficiency(Fv/Fm), actual light transformation efficiency(φPSⅡ)and protease activity kept a higher level. During the mid-late phase of grain filling the ability of eliminating reactive oxygen species decreased faster and the membrane of cell damaged seriously, that accelerated the flag leaf senescence and shortened the flag leaf effective duration. This went against accumulation and translocation of dry matter and nitrogen after anthesis. |
