Effect Of Glyphosate On Soil Weed Seed Bank And Physiological Responses Of Resistant Weed

Glyphosate is a organic phosphate herbicides developed by Monsanto company, because of its characteristics like stable physics and chemistry character, low toxicity, low residue and so on, and further increasing of glyphosate application in non-tillage fields, reduced tillage fields and Direct seeding paddy fields by using directed spraying technology, and also with the development andextension of glyphosate-resistant crops, glyphosate usage has been become to the largest in the world. With the continuous increasing usage of glyphosate and appearence of glyphosate-resistant weeds worldwide, study on weeds quantity characteristics and weed species dynamic change, and resistant weeds in seed bank after glyphosate repeated application becomes to be extremely important. This article revealed weeds quantity characteristics and species change in weed seed bank after glyphosate repeated usede, and preliminarily ensured the effects of Glyphosate on physiology in Equisetum arvense. The results showed as bellow:1. Under simulate pot culture condition after glyphosate four times repeated application the total number of weeds seed in soil seed bank significantly reduced. Some weeds species such as Amaranthus retroflexus L., Chenopodium album L., Abutilon theophrasti Medic., Oxalis corniculata L., Xanthium sibiricum Patrin., Artemisia scoparia Waldst.et Kiag. and Eriochloavillosa(Thunb.) Kunth, weed density and occurred frequency of Amaranthus retroflexus L., Abutilon theophrasti Medic. and Equisetum arvense L. in black soil of Harbin has no significant change, and others such as Amaranthus retroflexus L., Chenopodium album L., Commelina communis L., Chenopodium scoparia L., Xanthium sibiricum Patrin., Portulaca oleracea L., Erigeron canadensis L. and Polygonum bungeanum Turcz.in in albic soil from Shan Jiang plain also has no significant change.Under field experiment condition glyphosate four times repeated application the total number of weeds seed in soil seed bank significantly reduced. Some weeds species such as Chenopodium album L., Artemisia sieversiana Willd., K Sonchus brachyoths DC., Chenopodium scoparia L. Cephalanoplos segetum(Bge.)Kitam., Amaranthus retroflexus L., Cyclachaena xanthifolia(Nutt.) Fresen, Glycine soja L. and Digitaria sanguinalis (L.)Scop. has no significant change.Weed density and emergence frequency of some species such as Chenopodium album L., Artemisia sieversiana Willd., Chenopodium scoparia L., Glycine soja L., Amaranthus retroflexus L. and Rumex patientia L. has no notable change.2.7day and14day after glyphosate treatment (DAT) shoot fresh weight and dry weight of Equisetum arvense was notable inhibited, and shoot dry weight recovered at21DAT. There are no significant effects on rootstock fresh weight and dry weight by glyphosate in Equisetum arvense.3. Chlorophyll content was notablely inhibited at7DAT and14DAT after glyphosate applicated and with the glyphosate usage increasing the inhibition ratio increased. Chlorophyll content recovered to normal level at21DAT after glyphosate applicated.4. At14DAT after glyphosate post application at615g.a.i./hm2and1230g.a.i./hm2use rate the peak inhibition on nitrate reductase activity was found and the inhibition ratio is47.37%and49.61%respectively. Nitrate reductase activity recovered at28DAT. Nitrate content in Equisetum arvense was significantly enhanced at7DAT,14DAT and21DAT, and until at28DAT nitrate content recovered to normal level.5. There is no effect of glyphosate on ferrous reductase activity in marestail rootstock. ferrous content has no change at7DAT and28DAT after glyphosate application and ferrous content significantly increased at14DAT and21DAT. No affect on magnesium content in marestail through entire experiment period.6. Shikimite content has no significant changes after glyphosate post application at615g.a.i./ha and1230g.a.i./ha and showed this is the key reason of Equisetum arvense resistant to glyphosate.