-Abutilon theophrasti and Barnyardgrass (Echinochloa crus-galli) are major weeds that affect cropping systems worldwide. Laboratory and greenhouse studies were conducted to determine the effects of temperature, pH, water and salinity stress, and planting depth on seed germination and seedling emergence of Velvetleaf and Barnyardgrass. For Velvetleaf, the base, optimum and ceiling germination temperatures were estimated as 5, 35 and 48 o C, respectively. Seed germination was sensitive to drought stress and completely inhibited by a potential of -0.6 MPa, but it was tolerant to salinity. Salinity stress up to 45 mM had no effect on the germination of Velvetleaf, but germination decreased with increasing salt concentration. Drought and salinity levels for 50% inhibition of maximum germination were -0.3 MPa and 110 mM, respectively. Seed germination of Velvetleaf was tolerant to a wide range of pH levels. For Barnyardgrass, the base, optimum and ceiling germination temperatures were estimated as 5, 38 and 45 o C, respectively. Seed germination was tolerant to drought stress and completely inhibited by a potential of -1.0 MPa. Salinity stress up to 250 mM had no effect on seed germination. Drought and salinity levels for 50% inhibition of maximum germination were -0.5 MPa and 307 mM, respectively. A high percentage of seed germination was observed at pH=5 and decreased to 61.5% at acidic medium (pH 4) and to 11% at alkaline medium (pH 9). Maximum seedling emergence of Velvetleaf and Barnyardgrass occurred when the seeds were placed on the surface of the soil or at a depth of 1 cm.Keywords: pH, planting depth, seed germination, temperature, weed.RESUMO -Abutilon theophrasti e Echinochloa crus-galli são as principais plantas daninhas que afetam os sistemas de cultivo em muitas partes do mundo. Estudos em laboratório e em casa de vegetação foram conduzidos para determinar os efeitos da temperatura, pH da água e estresse salino e da profundidade de semeadura na germinação e na emergência das plântulas de A. theophrasti e E. crus-galli. Para A. theophrasti, as temperaturas de base, ótima e de teto de germinação foram estimadas em 5, 35 e 48 o C, respectivamente. A germinação das sementes foi sensível ao estresse hídrico e inibida completamente por um potencial de -0,6 MPa, mas foi tolerante à salinidade. Estresse salino de até 45 mM não teve nenhum efeito sobre a germinação de A. theophrasti, porém esta diminuiu com o aumento da concentração salina. Os níveis de seca e de salinidade para 50% de inibição da germinação máxima foram de -0,3 MPa e 110 mM, respectivamente. A germinação das sementes de A. theophrasti foi tolerante a uma vasta gama de níveis de pH. Para E. crus-galli, as temperaturas de base, ótima e de teto de germinação foram estimadas em 5, 38 e 45 o C, respectivamente. A germinação das sementes foi tolerante ao estresse hídrico e inibida completamente a um potencial de -1,0 MPa. Estresse salino de até 250 mM não teve efeito sobre a germinação das sementes. Os níveis de seca e de salinidade para 50% ...

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High performance liquid chromatography method was used to analyze six phenolic acids in 15 rice cultivars hull water extracts as representative cultivars collected according to the results of our previous study. Dinorado hull extract had the highest phenolic acid content among the treatments. None of the six phenolic acids were detected in Line-229 hull extract by HPLC, while, Dashti-sard had the highest p-hydroxy benzoic acid content. Phenolic contents had significant correlation with percent inhibition of root growth of barnyardgrass. Eleven of the tested cultivars were chosen and grown in hydroponics system to study their root exudates effects on growth traits of barnyardgrass seedlings, in a completely randomized design with four replications. Root exudates of Dinorado, Neda, Domsorkh and Dular showed the highest inhibitory activities of barnyardgrass growth parameters, while Line-229 root exudates had the highest stimulatory effects on growth traits of this plant. Rice root exudates obtained from nine cutivars hydroponics were also qualified and quantified with HPLC method. No vanilic acid or ferulic acid was detected in cultivars root exudates. Anbarbu, Usen and Dasht rice root exudates had the highest, and Line-229 had the lowest amount of the total phenolics content.

To assess the effects of IAA and Kinetin plant growth regulators in order to improve the drought tolerance in rice seedlings (Oryza sativa L.), a factorial experiment was carried out based on complete randomized design with three replications. The experimental factors included different rice genotypes ['Gharib', 'Khazar',], drought stress from 1 to 4 code of the Vergara coding system and control (normal irrigation) and growth regulators in three levels (IAA and Kinetin through foliar spraying and non-application as control). The results indicated, under normal irrigation condition together with IAA application, 'IR83750' rice genotype had the highest number of tillers and leaf greenness, with mean of 18.27 and 49.46, respectively. The highest amount of leaf relative water content (95.11%) was related to 'Sepidrood'. Under drought stress condition, the highest electrolyte leakage (36.59%) was observed in 'Gharib'. In drought condition, the highest leaf drying score was related to 'Gharib' in both years, but the highest score of leaf rolling index (9) was observed in 'Gharib' and 'Khazar'. The present findings showed that drought stress had harmful effects in all examined genotypes and the impact in susceptible genotypes ('Gharib' and 'Khazar') was more than 'IR83750' and 'Sepidrood'. Application of growth regulators (IAA and Kin) improved growth conditions for of all genotypes. Therefore, using tolerant genotypes along with growth regulators can improve the rice growth traits.

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Chlorsulfuron at 0.018 kg ai/ha, metsulfuron at 0.0045 kg ai/ha, and 2,4-D at 1.1 kg ae/ha plus dicamba at 0.28 kg ae/ha were applied over snow-covered winter wheat to study the feasibility of combining herbicides with a graphite snow-removal treatment. Chlorsulfuron or metsulfuron applied on snow effectively controlled annual broadleaf weeds when tank mixed with urea ammonium nitrate (UAN) at 28 kg N/ha and graphite powder at 20 kg/ha. Over-snow treatments of 2,4-D plus dicamba plus UAN did not control weeds. There was no antagonism or synergism among herbicides, UAN, or graphite.

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