Exogenous Applications Of Gibberellin Into Maize Field For Inducing Weeds And Orobanche Spp. Seeds Germination

Broomrape（Orobanche spp.）is a kind of holo-parasitic weed which parasitizes plant roots,has caused serious impact on agricultural production.In C hina,the most serious damage is due to the two kinds of Orobanche spp.that is O.aegyptiaca and O.cumana.At present,trapping crops is one of the effective ways to control Orobanche.It is a green and safe control method to stimulate the germination of Orobanche by trapping crops,because it can’t make Orobanche to parasitize.It can’t find the host to make Orobanche"suicide germination"in a short time.It can eliminate the seed bank of Orobanche and achieve the purpose of effective control of weeds.There are many kinds of trapping crops.Maize,as one of the three major food crops in the world,has the function of controlling Orobanche.Xinjiang Uygur Autonomous Region is one of the most seriously damaged areas by Orobanche spp.in C hina,and it is also the planting area with the largest high yield potential of maize in China.In this study,O.aegyptiaca and O.cumana seeds were used as experimental materials to explore whether gibberellin,maize and associated weeds have synergistic effect on the two kinds of Orobanche seeds.The effects of gibberellin on the growth of maize and weeds were studied through the combination of indoor and field experiments.Then the stimulating effects of gibberellin and weeds on the germination of Orobanche seeds were examinated,and finally counts the next crop hosts through rotation experiments Thus,the feasibility of using gibberellin to stimulate maize and associated weeds to induce Orobanche seed germination was preliminarily verified,so as to achieve efficient"trapping"effect and reduce soil seed bank of Orobanche.The main conclusions of this study are as follows:（1）The application of gibberellin in the field can break the seed dormancy in the weed seed bank,increase the number and species of weeds,and promote the growth of maize and weeds.The species and quantity of weeds increased significantly after spraying gibberellin.There were 11 different types of weeds in the plots sprayed with gibberellin.There were 7 different types of weeds in the control plot.The results showed that the total fresh weight,aboveground fresh weight and aboveground dry weight of weeds increased by more than 10%compared with the control.The results also idicateded that gibberellin could promote the growth of maize in the field,and the ear length,dry weight of ear,100 grain weight,plant height,stem diameter and stem dry weight of maize were higher than those of no gibberellin treatment.（2）The extracts from the roots or shoots of common weeds in maize field can stimulate the seed germination of O.aegyptiaca and O.cumana,but there are species differences,and they are greatly affected by the concentration.Among the 11 weeds,except Echinochloa crusgalli,the germination rate of the seeds stimulated by the distilled water extract from the shoots of other weeds was more than 30.0%,and the germination rate of the seeds stimulated by the methanol extract of all weeds was more than 35.0%;Except Chenopodium glaucum,Acalypha australis.,Setaria viridis and Abutilon theophrasti,the germination rate of O.aegyptiaca seeds stimulated by distilled water extract from the shoots of other weeds was more than 20.0%,and the germination rate stimulated by methanol extracts of other weeds was more than 30.0%except Abutilon theophrasti;With the exception of Echinochloa crusgalli and Setaria viridis,the germination rates of the O.cumana seeds stimulated by distilled water extracts from the roots of other weeds were more than 35.0%,while the germination rates stimulated by methanol extracts from the root s of all weeds were more than 50.0%;Except the distilled water extracts of Convolvulus arvensis,Amaranthus retroflexus and Echinochloa crusgalli,the germination rate of O.aegyptiaca seeds stimulated by the extracts of other weeds was more than 20.0%,and the methanol extract could reach more than 50.0%.On the whole,the germination rate of the seeds stimulated by the extracts of the roots of weeds was slightly higher than that of the aboveground parts;the germination rate of the seeds stimulated by the extracts of d ifferent weeds was significantly different The best concentration of stimulation was different,but the 10 times dilution of most weed extracts had the strongest stimulating effect on the germination of two kinds of Orobanche seeds（3）Gibberellin can shorten the preconditioning time required for two kinds of Orobanche seeds and improve the germination rate.Soaking seeds with GA₃ can improve the germination ability,germination rate,germination potential and germination index of maize and its main associated weeds seeds,and can promote the growth of roots and buds of corn and some weeds in different degrees.The results showed that the germination rate of O.Cumana and O.aegyptiaca seeds preconditioned with 100μM GA₃ for 1 day could reach that of the control for 3 days and 5 days,respectively.After GA₃ preconditioning for 3 days,the germination rate of two kinds of Orobanche seeds reached the highest,while the control needed to be preconditioned for 5 days.Compared with the control,the germination rate of O.aegyptiaca seeds preconditioned with 100μM GA₃ increased by 5%-11%.（4）Pot rotation experiment was conducted to verify the effect of gibberellin stimulation on O.aegyptiaca seed germination induced by maize and associated weeds.Compared with the treatment of sowing maize alone and not applying GA₃,under the condition of maize and weeds symbiosis,applying 100μM GA₃ reduced plant height by 0.5%,increased stem diameter,shoot dry weight and root dry weight by 8.1%,7.1%and 4.6%,respectively;The aboveground dry weight of weeds decreased by 36.9%,and the root dry weight increased by10.0%;At the same time,it had no effect on the plant height of the next crop processing tomato,but increased the aboveground and root biomass,and the existence of the previous crop roots would increase the plant height and aboveground dry weight of each treatment.The epigaeous number,hypogeal number,attached number and dry weight of O.aegyptiaca seeds decreased by 87.5%,41.7%,53.1%and 65.2%,respectively.