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Vol. 16—1962 - NorthEastern Weed Science Society

Vol. 16—1962 - NorthEastern Weed Science Society

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pel'fQ.,..d,-.ear17M1932. that the administl'&tto.a of auxin to certain<br />

tnes otplUtceUsresults'1n;III'1,1ncrease inth.'l'1a.ttic extensib1l1tyot<br />

the1f8ll.-Sinee, .. we haveedd.htore,the Wall constrains the protoPlU­<br />

1110' contentll:.in their growth, a loosening up ot wa1l structure could lead to<br />

stretc~;of tbeceU under the 1Iitluenceot intemar' turgor pressure.<br />

This. 1s .the:lnterpNtation usU4lJ.T-J;sLvento explaiD"the cell extension pre;..<br />

mot1ng actJivi1l7 ,otauxln.· ' .<br />

iUntol'tunatel;rth1s cannot be the ClOI'IIpleteanewer. wemow, tor exa»­<br />

ple, that auxin promotes division of many cells in the plant. Manyyears<br />

ago, it became clear that cambial divisions in ~ spring were initiated by<br />

auxin OOIIIingtmll the growing bu6' above. TbSue ~tures of cambiai' and<br />

other ceUa trequentlT require an endogenous source: ot natul'al or art1t1~tal .<br />

auxin for tbecont:Uwation of cell division. The initiation of adventitious<br />

root., "hich 1nvol"'. celldiV:1e1cmin the per!ctele, i. also caused br.' ,<br />

auxin •. Clearl, then 'cell diTiision promoting .actiOO8 c;annot be attributed<br />

to the wall. In hot, since one generelly thinkllot the nucleus as the 1b1­<br />

tiator of the cell division cycle, one is tempted here 'to regard the nucleus<br />

as the intracellular locale of auxin action.<br />

But eventhb picture is not Oomplete. ~~ thirty years ago, Th1- .<br />

mann·aI1dsWeene;r,worldng with thecel18 of ~Coleqptiles, sb:lwed that<br />

the applicaUo*'o! awd.ntOauxf~t1cient c~li.wQUL~ initiate protopJ.Umic<br />

stream1ni':~ thatremovalot,.aux:l.n would1'$iE!ult tn a diminution ot. protoplasmic<br />

eti'ftla:l.ng~ . The~le aspect ot t~(·~~trol is that it CU1<br />

be ·exerted within several minutei. To what organeU8are we to look here?<br />

What is it that controls cytopl&lllll1,cstreaming? In :t~t we do not mow•.<br />

Th.. olosest we'canoalle is to 8~ that cytoplasm1c·.'t~am1l'!8 is quite obvioulJl7<br />

dependent 'on·an energy supply and an 8lttern~s~ply ot OJq'gen. Since<br />

it is the m1tochOndrion in which rtlspiratory activ1.tyl,s localized, we are<br />

tempted to consider the ml.tochondr1on as the seat.9.f plant hormone actien in<br />

this instance. Or perhaps we should look to the so-called "structure!es8<br />

cytoplasm. II<br />

In factex.per1ments pertoJ"llBd,lD8n1years ago ,!?yHenry Northen sho,e4<br />

that the eppllcatiOfl ot auxins to

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