Abstract: Based on field experiments with two rice cultivars,Yangdao 6 and Nanjing 43 under different high temperature stresses(35℃/3d,35℃/5d,38℃/3d and 38℃/5d)at heading stage,authors analyzed the relationships between dry matter accumulation and distribution,soil and plant analyzer development value(SPAD)and net photosynthetic rate(NPn).The results showed that SPAD value,net photosynthetic rate and dry matter accumulation declined gradually,the export percentage of the matter in stem-sheath(EPMSS)and the transformation percentage of the matter in stem-sheath(TPMSS)increased gradually by high temperature stresses compared with CK.With the elevation of stress temperature and extension of stress time,decreasing extent or increasing extent of the above indexes of two rice cultivars increased sharply.Different rice cultivars respond differently to high temperature stresses,the ability of high temperature tolerance of Nanjing 43 was lower than that of Yangdao 6.

Key words: High temperature stress, Yangdao 6, Nanjing 43, Photosynthetic characteristic, Dry matter accumulation, Soil and plant analyzer development value, Net photosynthetic rate