Comparative Analysis of Dry Matter Accumulation Changes between Old and New Rice Cultivarst

Four older（released in 1960s）and four newer（released since 1990）rice cultivars were planted in field.Biomass of single plant，leaf，stem and sheath and panicle were measured.Relationship between dry matter accumulation and yield was studied in each growing stage.Results showed that biomass of single plant，leaf，stem and sheath and panicle of older and newer cultivars changed in different ways.In the whole growing stage，biomass of leaf was achieved positive correlation with the yield，especially achieved significant positively correlation level at the tillering stage and milky stage.Relevance between biomass of stem and sheath and yield had wider fluctuation.Biomass of stem and sheath were significantly negatively correlated with yield in the shooting period，and in the heading stage achieved significant positively correlation level，in the rest stages was positively correlation.Biomass of panicle kept significant positively correlation with yield in all the growing stage，which showed the yield growth.