Seed Biology,Seedling Abiotic Stress And Chemical Control Of British Timothy(Pheleum Paniculatum)

This study is focused on seed biology,seedling abiotic stress and chemical control of British timothy(Phleum paniculatum),which is a new infested malignant weed in local wheat field of China.This study may explain the reason Phleum paniculatum has the ability to widely spread and infest in China.In this paper,the seed biology of Phleum paniculatum was studied,including seed dormancy,factors affecting germination,moisture content and fructifying traits characteristics;the influences of temperatures,water,and salinity stresses on seedling growth of Phleum paniculatum were explored;as well,the sensitivity of Phleum paniculatum to wheat and non-wheat fields herbicides was conducted by whole-plant bioassay and available techniques used for chemical control of Phleum paniculatum were studied in laboratory.Main results were:1.Seed BiologyPhleum paniculatum seeds had a shallow dormancy about 20?30 d when stored at room temperature.The dormancy could be broken fast when buried underground 5 cm,while a low storage temperature 4?C aintained seed dormancy.Seeds could germinate between 10? and 25?,except for 5? or 30?,and the optimum temperature was 15?20?.Germination percentages were all>88%when seeds were placed at 25/15?25/10?20/15?20/10?15/5?,except 10/50C and 30/20?.Light was not essential for seed germination,and different light periods had no significant effect on the germination.PH values from 4 to 10 did not inhibit germination.Phleum paniculatum seeds germination was moderately adaptable to NaCl concentration,but sensitive to water potential,and germination rates would be decreased 50%when water potential was-0.42 MPa or NaCl concentration was 113 mmol·L-1.Increased soil burial depth decreased the seedling emergence,and no seeds emerged when the burial depth was more than 4 cm.Seeds could still germinate under 6 cm but failed to emerge.Phleum paniculatum seeds had a lower moisture content and the average water content was 10.88±0.17%.Its average length of spike was 5.46±0.13 cm,average number of seed per spike was 474.30±16.55,average height of plant was 58.83 ± 1.81 cm,the number of effective tillers was 4.20 ± 0.34,and average 1000-grain weight was 0.1712±0.02 g.2.Seedling abiotic stressUnder 35? high temperature,chlorophyll content in Phleum paniculatum young leaves was declined,while the protein content decreased first and then increased,the activities of SOD and POD increased significantly then decreased,the activity of CAT increased first and then decreased then increased,and CAT activity changed non-significantly.Under a low temperature of 0?the content of chlorophyll had been increasing at first seven days and then decreased,the protein content increased first and and then decreased,,the activity of SOD,POD and CAT increased first and then decreased.When Phleum paniculatum seedlings were treated at 200 mmol·L-1 NaCl,the contents of chlorophyll and protein increased significantly,and the activities of SOD,and POD all increased,but the activity of CAT increased first and then decreased.Under the osmotic stress of-0.8 MPa,the content of chlorophyll and protein of Phleum paniculatum seedlings had been increasing with treatment time,the SOD activity decreased first and then increased then decreased,POD and CAT activity first increased and then decreased.It shows that Phleum paniculatum seedlings could sustain a certain level of environmental stress,such as low temperature,salinity and osmotic stress.3.Chemical ControlThe susceptibilities of Phleum paniculatum to 12 soil-applied herbicides and 14 foliar-applied herbicides were tested by whole-plant bioassay in laboratory.The results revealed that the soil-applied herbicides,such as diflufenican,isoproturon,chlortoluron,pretilachlor,and foliar-applied herbicides,including clodinafop,pinoxaden,pyroxsulam,tralkoxydim,isoproturon,amicarbazone had preferable effect on controlling Phleum paniculatum.Their ED90 values were all below their recommended doses respectively and Phleum paniculatum could be controlled effectively at their recommended doses.Phleum paniculatum was not sensitive to fenoxaprop,mesosulfuron,bispyribac-sodium,pyribenzoxim,isoxaflutole or benthiocarb.The optimum formulation with low costs and high efficacy for controlling Phleum paniculatum was screened using Gowing's method and isoble method.Two optimum formulations were obtained as:flufenacet:diflufenican(1:2)and florasulam:tralkoxydim(1:20).Two groups of the mixtures were applied in greenhouse and these two formulations had preferable control efficacies on the main principal weed in wheat fields and safed for wheat.