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In order to understand the relationship between source and sink in soybean cultivars released in different years, we studied 20 soybean cultivars representing genetic progress in Jilin Province from 1923 to 2005. The experiment was conducted in a random complete block design with three replications. Results showed that soybean seed yield increased significantly with year of release, it was increased by 113. 1 % in past 82 years (1. 38% per year) according to the calculation of regression equation. Leaf area per plant and net photosynthetic rate ( Pn ) were measured at R2 stage. Yield, number of pods, number of seeds and weight of pod were measured in each plot at maturity ( R8 stage ). The increase of soybean yield was strengthened by source and sink. Leaf area and Pn were increased by 27. 76% and 21. 56% during the genetic improvement of 82 years, and were increased by 0. 34% and 0. 26% per year respectively. Number of pods, number of seeds and weight of seed increased 44.33% ,80. 1% and 59.5% , which were equivalent to 0.54% , 0. 98% and 0.73% respectively in each year. As the increase in ratio of sink to source, the number of seeds per unit leaf area, weight of seed per unit leaf area were increased by 50. 86% and 56. 45% during 82 years, and increased by 0. 62% and 0. 69% per year respectively. As the results, the number of blighted pods was increased by 314% , which was an increase of 3. 83% per year. Our results showed that soybean breeding for high yield had resulted in unbalance increase of source and sink, soy- bean high yield breeding should be focused on harmonizing the source and sink. Improving leaf Pn may be more beneficial in the future soybean high yield breeding. [ABSTRACT FROM AUTHOR]

Abstract: To understand the changes in yield, harvest index (HI) and biomass of aboveground parts of rice, 33 japonica rice cultivars released from 1958 to 2005 were planted. During the 47 years, the grain yield increased from 9 118.36 to 15 060.1 kg/hm2 and HI from 0.46 to 0.55. In the genetic improvement, the total number of tillers per plant decreased, and the biomass per unit area slightly increased at the harvest stage. The increases of yield and HI resulted from the increased biomasses of effective tillers and single stem, and the increase of biomass per stem was related to the increased biomasses of different organs along with the genetic improvement. The stem and sheath biomass at heading and the leaf biomass at 30 days after heading showed the highest increase, up by 75.17% and 49.94%, respectively. The biomasses of leaf and stem-sheath at 10 days after heading, and biomass per stem at 30 days after heading were obviously correlated with the yield. The results indicate that the genetic improvement has resulted in the increase of yield and HI. This increase is correlated with the decrease of total tiller number per plant, and increase of biomasses of effective tillers and single stem. The leaf biomass after heading and the stem and sheath biomass at 10 days after heading can be used as selection criteria for breeding high yielding rice cultivars. [ABSTRACT FROM AUTHOR]