Vol. 16—1962 - NorthEastern Weed Science Society

Vol. 16—1962 - NorthEastern Weed Science Society Vol. 16—1962 - NorthEastern Weed Science Society

08.06.2015 Views

20 June. Applications ot .300,lblA over five dates dJ,u'ing the growing season gave' sO/Il8Whlltg;reater activitylete in the se~so~'bu:t ~d llOt' fullyoyercome the dormancy oote4 during the early l3ummerll1Ot?-tb~. T~ second tOI'lll ofciormancy is therefore related to an mremely JP.gh~~:r'gon-nitrogen ratio in the rhizome tissue.' '. , " , A third torm ot t'ormancy was shown by Meyer (9) to arise trom apical dominance. The inhibiting etfect was JOOstprono~d. uhen a shoot weBpresent, but this tom of d'Omancy co~ 1;>ed6Jl¥)nl3trateclOJl~{l1zomes sections ~' when the sheot ,was r'en!oved. ,The buds on nodes ~ta1 trom the tip enved the least activ:i.,ty.Thef.act tbat all budtl pos~,s the same ciegreeQ!:IlCtivity inherently ~l8.sd8Jl¥)nstrsted'bycuttingthe rhizoM- int-o single node sect1ons. TA/henthis was dbne, ~e buds t1'omthe various lop.j;,~ons on the rhizO/I1e,sbowed equal activity ,!t1d IGadeequal shoot growth. While it can be demonstrated that apical doMinance exists in quackgrass, it was tound ,this, diq,no,t acCount tor all ot the ~ dQrmsncy noted in the tield. Meyer (~) 'rembved th~ s_~

5. llslapon and other chlorine,ted organic !lciQs,iS:well as MIl, reduoed wot growth of ~8Ckgress drastically, but did not IlI8terially reduce bid dormancy is otten cited as the mechanism involved. A IIIOreexact evaluation "-" ot the response atter treatment with the chlorinated aliphatic acids is that bud activity is in fact maintain"', but thet the shoot growth is sharply reduced. The dsstruction of shoot growth after trea_not, with dalapon interrl1pts photosynthetic activity and some reduction in carbohydrate occurs, but at a rate MUChslower than in the case of plants treated:'wit,h atruine or amitrol because the respiratory activity!s lower. The residue of dalapon in the soil and in" the tissue is dissipated rather quickly and after a period of several, months partial regrowth .-y occur. This regrowth develops from buds that have remained inactivewb1le the dalaponwes present. Shoots that do devebp are apt to grow vigorously because of the relatively high carbohydrate reserve that has been lIl8inte1ned in the rhizome. The bud response followi~t~tment withMli is somewhat siJnilar to that observed with dalapon. Zick (16)' snd i1eyer (9) both found that bud activity was not altered lnaterially, but that the shoot growth was greatly reduced. Maximumresponses occur only under conditions that fmr absorption ofb chemical. Applications of MHdo not destroy t,h.' folia,ge so carbohydrates continue t~ accumulate. The maintenance of,th~ shoote also serves to maintain a considerable degree of apical dominance. Eventually inactive buds on the rhizome are releued and when t!lis occurs, teg;rowtb, is abundant and vigorous. 21 1. Quackgrass is a widely distributed and persistent weed in the northern states and ilj. Canada. The plant spreads zoap:l.dlNb1 both seeds and ridzomefragments. ' The rhizomes are abundant in t,he surface soil and " normally maintain a total available carbohydrate content of 40% or I1lOre during the year. This, along with an abut1-dant'lUpply ot inactive bU~ , on the rhizomes, assures vigorous and persi,stent,regrowth after de!o]J;ation. 2. Qusckgrass plants treated wi.th,atrazine show marked reductions in the 'total available carbohydrates in ,the rhizomes. The speed of carbo~te reduction 'is accelerated by maintBining shoot growth on treated plants and by adding nitrogen when a def~ciency ot ~e element occurs.! major r.esponse ot quackgrass to ,am1trol also in-volvesthe depletion of carbohydrate in the rhizomes. Amitrol may not persist in the active form in the tissue long enough to deplete the resel"VQ to the lethal point. 3. The activity of vegetative buds en quackgras's rhizomes is reduced or limited by (1) temperatures above 25 C,(2) w1dec.rbon-nitrogen ratios in the rhizome tissue dUring late spring, and enapical dominance of shoots or terminal buds. 4. '!'he growth substances inql.l8ckgrass mq be .~ lliaterid other than IAA for this cotnpoimdhad no detectable effect on the activity of vegetative buds. TIBiI.IOOdJ.1'i.edpolar transport of bud irJhj:biting tectors while NAAand various herbicides inhibi t~ or, el1ilQ.nated bud ecti vi ty.

20<br />

June. Applications ot .300,lblA over five dates dJ,u'ing the growing season<br />

gave' sO/Il8Whlltg;reater activitylete in the se~so~'bu:t ~d llOt' fullyoyercome<br />

the dormancy oote4 during the early l3ummerll1Ot?-tb~. T~ second tOI'lll ofciormancy<br />

is therefore related to an mremely JP.gh~~:r'gon-nitrogen ratio in the<br />

rhizome tissue.' '. , " ,<br />

A third torm ot t'ormancy was shown by Meyer (9) to arise trom apical<br />

dominance. The inhibiting etfect was JOOstprono~d. uhen a shoot weBpresent,<br />

but this tom of d'Omancy co~ 1;>ed6Jl¥)nl3trateclOJl~{l1zomes sections ~'<br />

when the sheot ,was r'en!oved. ,The buds on nodes ~ta1 trom the tip enved<br />

the least activ:i.,ty.Thef.act tbat all budtl pos~,s the same ciegreeQ!:IlCtivity<br />

inherently ~l8.sd8Jl¥)nstrsted'bycuttingthe rhizoM- int-o single node sect1ons.<br />

TA/henthis was dbne, ~e buds t1'omthe various lop.j;,~ons on the rhizO/I1e,sbowed<br />

equal activity ,!t1d IGadeequal shoot growth.<br />

While it can be demonstrated that apical doMinance exists in quackgrass,<br />

it was tound ,this, diq,no,t acCount tor all ot the ~ dQrmsncy noted in the<br />

tield. Meyer (~) 'rembved th~ s_~

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