Effects of Different Species in Echinochloa on Photosynthetic Characteristics and Grain Yield in Rice under Alternate Wetting and Moderate Drying Condi-tion

Abstract

In order to investigate the effects of different barnyardgrass species on photosynthetic characteristic and grain yield of rice, two rice cultivars, Liangyoupeijiu (an indica hybrid cultivar) and Nanjing 9108 (a japonica cultivar), were co-cultured with four barnyardgrass species from transplanting to maturity under alternate wetting and moderate drying condition. The treatments were designed as follow: weed free (control), rice with Echinochloa crusgalli var. mitis (T1), rice with Echinochloa crusgalli (T2), rice with Echinochloa crusgali var. zelayensis (T3), and rice with Echinochloa colonum (T4). The results showed that the degree of interference of barnyardgrass on rice yield depended on different barnyardgrass species and rice cultivars. The interference intensity of barnyardgrass was in the order of T3>T1>T2>T4, and grain yield loss rate in Liangyoupeijiu was less than that in Nanjing 9108. T1, T2, T3, and T4 treatments respectively reduced 11.16%-13.78%, 10.19%-10.60%, 19.00%-23.79%, and 0.50%-1.57%, for Liangyoupeijiu of the grain yield and 38.44%-45.51%, 31.29%-36.86%, 54.88%-60.65%, and 8.28%-15.14% for Nanjing 9108, T1, T2, and T3 significantly reduced rice grain yield, while the effect of T4 was significant for Nanijng 9108 but not for Liangyoupeijiu when compared with CK. Moreover T1, T2, and T3 had no effects on leaf area index and contents of photosynthetic pigments for Liangyoupeijiu, but Nanjing 9108 significantly reduced leaf area index and increased contents of photosynthetic pigments under the same treatment condition. Furthermore, four treatments significantly reduced rice canopy light transmission, leaf photosynthetic rate, stomata conductance, transpiration rate and dry matter accumulation during grain filling stage. The results indicated that the decrease in canopy light transmission, photosynthetic rate, transpiration rate, stomata conduc- tance and the increase in some degree in contents of photosynthetic pigments during grain filling stage may contribute to grain