[Differences in exogenous methyl jasmonate-induced quinclorac resistance between resistant and sensitive barnyardgrass and the underlying mechanism]. / å¤–æºèŒ‰èŽ‰é ¸ç”²é ¯è¯±å¯¼æŠ—æ€§ä¸Žæ•æ„Ÿç¨—è‰å¯¹äºŒæ°¯å–¹å•‰é ¸æŠ—æ€§çš„å·®å¼‚åŠæœºç†.

The effects of exogenous methyl jasmonate (MeJA) on the resistance levels to quinclorac and endogenous hormone levels were examined using the resistant and sensitive biotypes of barnyardgrass with the same genetic background. The results showed that exogenous MeJA could significantly increase the resistance of resistant plants to quinclorac, but did not affect the resistance of sensitive plants. There were significant differences in the contents of indole-3-acetic acid (IAA), abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA) among the tested materials. Quinclorac treatment could significantly increase the contents of ABA, SA, and JA in barnyardgrass, with stronger increase of ABA and JA contents in the sensitive plants. Exogenous MeJA could significantly enhance the induction of ABA and JA contents by quinclorac, especially in the sensitive biotypes. These results showed that rapid hormone variations in sensitive plants inhibited their response to herbicide, while gentle hormone variations endowed resistant plants with a strong adapta-bility to herbicide, which closely related to the enhanced resistance by MeJA. ABA and JA hormone signals might play an important role in the resistance of barnyardgrass to quinclorac stress.

[Effects of different baynyardgrass varieties on grain yield formation of rice at different nitrogen application levels.] / 不同氮水平下不同种稗草对水稻产量形成的影响.

This study aimed to investigate the effects of different barnyardgrass varieties on yield formation of rice. A Japonica rice cultivar, Nanjing 9108, was used and co-cultured with three barnyardgrass varieties from transplanting to maturity under different nitrogen (N) levels of 0, 120, 240, and 360 kg N·hm-2, taking baynyardgrass free as control. The three barnyardgrass varieties were Echinochloa crusgalli var. mitis, E. crusgali var. zelayensis and E. colonum. The results showed that, at the same N level, the plant height of the three barnyardgrass varieties was E. crusgali var. zelayensis > E. crusgalli var. mitis > E. colonum, and the growth duration was E. crusgalli var. mitis > E. crusgali var. zelayensis > E. colonum. The biomass of baynyardgrass increased with the increase of N application rates and reached a peak at the N rate of 240 kg N·hm-2, and it decreased at 360 kg N·hm-2. The biomass of either E. crusgalli var. mitis or E. crusgali var. zelayensis was significantly higher than that of E. colonum. At the 0 kg N· hm-2 level, all barnyardgrass varieties showed no significant effect on rice yield. At the 120 kg N· hm-2 level, rice yield was not significantly different among the three treatments of barnyardgrass free, co-cultured with E. crusgalli var. mitis, and co-cultured with E. colonum, but it was significantly decreased when co-cultured with E. crusgali var. zelayensis. At the 240 kg N·hm-2 level, all treatments of co-cultured with barnyardgrass significantly decreased the rice yield. At the 360 kg N·hm-2 level, rice yield was significantly decreased under the treatments of co-cultured with E. crusgali var. zelayensis or with E. crusgalli var. mitis, and showed no significant difference between barnyardgrass free and co-cultured with E. colonum. All these data indicated an interaction between barnyardgrass and N fertilizer, which mediated the formation of grain yield of rice. Furthermore, at the 120 kg N· hm-2 level, the co-cultured E. crusgali var. zelayensis treatment significantly reduced leaf nitrate reductase activity and photosynthetic rate and root oxidation activity during the grain filling period, and decreased nitrogen accumulation and dry matter accumulation at the maturity stage, but other two treatments showed no significant effect when compared with barnyardgrass free treatment. These physiological indices of rice were significantly reduced by both E. crusgalli var. mitis and E. crusgali var. zelayensis treatments at either 240 or 360 kg N·hm-2 level, and showed no significant difference among all treatments at the 0 kg N·hm-2 level. Regression analysis showed that the order of effects of barnyardgrass phenotypes on rice grain yield was biomass, plant height, growth duration and tiller number. All these results suggested that the coexistence with large biomass of barnyardgrass inhibited the leaf photosynthetic rate, nitrate reductase activity, root oxidation activity, nitrogen accumulation and dry matter accumulation of rice, and consequently, reduced the rice grain yield.

[Effects of different barnyardgrass species on grain yield of rice and their physiological characteristics under alternate wetting and drying irrigation].

In order to investigate the influence of different barnyardgrass species on rice yield and physiological characteristics of rice, two rice cultivars, Liangyoupeijiu (an indica hybrid cultivar) and Nanjing 9108 (a japonica cultivar) , were employed to co-culture with four barnyardgrass species during the period from transplanting to maturity under alternate wetting and moderate drying ir- rigation condition. The treatments were separately designed as follow: weed free ( control) , rice with Echinochloa crusgalli var. mitis (T1), rice with E. crusgalli (T2), rice with E. crusgali var. zelayensis (T3) and rice with E. colonum (T4). The results showed that T1, T2, T3 and T4 treatments reduced the Liangyoupeijiu yield by 13.8%, 10.6%, 23.8% and 0.5%, but the corresponding yield loss of Nanjing 9108 could reach up to 45.5%, 36.9%, 60.7% and 15.1%, respectively. The results above showed that T1, T2 and T3 treatments all significantly reduced grain yield, and T4 treatment only reduced grain yield for Nanjing 9108 but not for Liangyoupeijiu. All treatments elevated malondialehyde contents of rice leaf, but the activities of peroxidase, catalase, superoxide dimutase, dry matter accumulation in maturity stage, root oxidation activities and contents of indole-3-acetic acid as well as zeatin + zeatin riboside in roots during rice grain filling stage were all decreased. The influence degree of four barnyardgrass against physiological indices of rice had the order of T3 > T1 >T2 > T4. It showed that the reductions in enzyme activities of antioxidant system, root oxidation activities, contents of indole-3-acetic acid, zeatin + zeatin riboside during grain filling stage and accumulation of dry matter in maturity as well as increase in contents of malondialehyde of rice during grain filling stage might be important reasons for grain yield reduction when grew with barnyardgrass.

[Influence of weeds in Echinochloa on growth and yield of rice].

In order to investigate effects of different barnyardgrass species on growth and yiled of rice, two rice cultivars, Xinliangyou 6 hao (an indica hybrid cultivar) and Nanjing 46 (a japonica cultivar), were co-cultured with four barnyardgrass species grown at a density of six plants · m(-2) from 10 days after transplanting to maturity. The treatments were designed as follow: weed free (control), rice with Echinochloa crusgalli var. mitis (T1), rice with E. crusgalli (T2), rice with E. crusgali var. zelayensis (T3), and rice with E. colonum (T4). The result showed that barnyardgrass-induced reductions in grain yield of rice were obviously different among the four treatments. T1, T2 and T3 treatments reduced the grain yield of indicia cultivar by 19.2%, 10.8% and 21.9%, and the respective reductions in japonica cultivar were 39.7%, 25.3% and 47.3%, re- spectively. However, no significant difference was detected for T4 treatment. During rice co-culture with barnyardgrass, T1, T2 and T3 significantly reduced rice dry matter accumulation at maturity, flag leaf photosynthetic rate, root oxidation activity and the activity of adenosine triphosphate enzyme (ATPsse) in rice grains at the filling stage, and the magnitude of decrease was in the order of T3 > T1 > T2, while no significant difference was observed between T4 and CK. In addition, all treatments had no effects on the final tiller number and plant height of rice. It indicated that the negative effect of barnyardgrass on rice growth and yield differed among the four species of barnyardgrass, in the order of T3 > T1 > T2 > T4. Barnyardgrass reduced the flag leaf photosynthetic rate of rice, both root oxidation activity and ATPsse activity in grains, which resulted in the reduction in final productivity of rice when co-cultured with barnyardgrass.