Water status and growth initiation in Populus : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University

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Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

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C"''il. ,..,...~"r('1

·~, .1. .:.·!... j vi.)

A tl::E::::ds preser. tcc.1 in partial fi;_lfi lr.icnt of the re,2_L~irements for the deg:colj of J·Iaster of

) .. gricul tural S~icr.ce j_n Pl~nt Scier,cc.

rassey Univcrzity

'dilliam Ross !7ath:.u:5.el Ed·.·rc;;.rds

197'i

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C i;

{ ·i l⁰⁾⁰ ⁾

\ -· .

S~~J~TARl

__

^..,,^_^_

- -

an,r;nl::t..~'!. id.

t.

cv. 'Co.ro lincmsi s'

A J.imi ted exu.::1il1a tion \~as rnade of t,w other :!'a.c tors - ihr~ effect of

licJit ,

ar:d the> i:ufJ.ue:'.'lc0 of exogenous avxin 011 ,~ro,,;th ini t:iation.

i

t.11 gro1-;t}; ex1jeriri1ents were carrie:c: out using a water culture h:.;.;h:;1:i.q_uo. S⁰asona.l ctc.:.ne;cs in wo.ter content D.nd. 1-ra·trr potential wc·rc mea:.,' .. n:·cd over the }K,riod of y_ui3scence. ;-111ter t;onte1:t was at a minir.n1Ia at 10::tf fall

and rose slowly until erowth ini tia1,ion. \fater potential rose slowiy to a muximur., in mitl-w.i.nter, a11c then i::Jowly fell-, Although uater c0nte;1t

was sit'1'Jjfica.,.1tly hicher at the top of wondi:; ~h.c1n at the bottom at Jcc;_f-['111., this Wb.3 redu~cd er eventually elim:i.1:ftted 'l·rith tl:.c general r1:.;c in wa7.er co,1tent, but there \;ere no corYespondine- differences in ,;-;ate:' potcntia:1 .•

Wnter l ::,ss w.:es cle.'.'.l'ly r~lated t o relative h11r:1ic.ity, and cut ends of a cutting were a ~ajor site cf evaporation. The presence of buds had a small effect, which was related io re}" i::i_'.r8 hur:idi ty both in di rect:i on and rac::.gni tude.

,'u:1 investigation of the effect r;f exogenous auxin sue;geste·1. that in P. an,.,.uJ.a ta root ·_;__ni tia tion may be liml. tcd by 1ow cndogenons levels of auin, b'.lt t i-1:i s 1-;as not confirmed. since auxi21 assays were not done.

Light was shown not to be a factor in the number~ of sheets and roots produc:~d, al".;h0¹lgh root i:.1~. tiation ,-ras delayed by the light treat1!1en t.3.

However, thzre was a s:i.gnific3.nt failure rate in the dark in a subsii tute Glone ( a hybrid. clone bre;d in Attst:ralia from Ponulus de ltoidP.~).

'11' 0

.: 1. ... effect o:f:' water stress on growth init-tation and early growth was

stn1ied using an osmoticum in wate;r:> culture of cuttings. The induced stress severely limi-:ed. both shoot and root growth which was very lo'l-r;

below - 4 bar. However, budbreak: occurrec. and root primo:..·dia deYelopeci in higher osmotic potentials, but bP-low - 11 bar there was little development.

Inter:1.al \·re.ter potentic.] an<l water c0nbi1t were ~ighly correlated vith

Sho'..:°ts and rcots were found to have water contents which were invP-rsely related to th2 osmctic potential of the growth 10e~ium.

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'fable ^{1 •} Table 2: 'l'a bJ. £>

3 :

'Va'ole

4:

Table

5:

Table

6:

Table

7:

ii

T,ist of 'I'.~

Paie Change of ¹·.'atC!r Content

at

^100;~^R.^H. ³⁸

Failure Rate of 'Aust. 135' in Diffe:rent Light 'l're11t:r.ents. 42

Pinal Dry :·!eights of noots.

55

Fin;,.l Dry ·,·.'eights of Shoots.

56

R13lation between i'later Content nnd ',-,'at.er Potc:-itial. 67 Incidence of Shoot and Root Gro~th. 68 Relation between Internn.l '.v~ter &h .. :;us and Growth. 82

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Fig.

.

I

.

•

Fig. 2:

Fig.

3:

Fig.

4:

Fig.

5:

Fig.

6:

Fig.

7:

Fig. 8:

Fig. ^Q^_,^,

.

List o~ Fj.r~n·cs

Heasurement of Se.:i.sonal ',fo.ter Stabi.:J: Plan of Subd:i.vioion of each Region of each ';:and.

Sensonal Water Statu::;.

Effect of Relative Fumi d.ity 0:1 ¹,\1-'"ltcr Content.

The Influence of Bud Presence on the Size of i'll1ter Lo:..·s at purticuler Relative Humidi tic~s.

Effect of Light on Shoot Growth. Effect of Light on Root Growth.

Effect of Exogenous Auxin 'on Shoot Growth.

Effect of Exogenous Auxin on Root Growth.

Water Potential of ·cuttings L.1 Growth Media of various Os~otic Po':entials.

Fig. 10: ~!a tor Content of Cuttings in Growth Media of various Osmotic

ii i.

2f.

35 37

48

~o

54

57

Potentials. 61

Fig. 1 ~ : Shoot Growth of Cut tines in Grm·1th l!edia of various Osn,otic

Potentials. 70

Fig. 12: Root Grm,rth of Cuttings in Growth I¹!edia of various Osmotic

Poten. tials. ^{. 76}

Pig. 13: Measurement at the Terr:iination of the experiment relating Gro~·,th

t o

Water Stress.

Fig. 14: Water Content of Shoots and Roots grown in media of ve.rio-..1s Osmotic Potentials.

7 9

80

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List o.f' P l ~

Plate 1: The Effect of

Lj cht

on Growth

Plate 2: The Eff2ct of Exogenous Auxin on Growt.h

Plate 3: Tr.c Effect 011 Dudbreak and Root Ini tintion of V9.rious

Parre 43

51

Osriotic Potentials .:isso'..-iated with the Growth I•:ediu:t. 73 Plate 4: Stoolbeds used in the Experimental Ser:.es as u source of

Plant Naterial

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V

'l'he bem~fi

t

of this study to myself was i1:1r.·.easurn.bJ.y .i.ncrea:-;cd by the guidance ai1.C care:t'ul instruction of my supervisor, I·:r. A.G. Robertson (Agrono;..'1y Dc1x.'1rt:;1cnt, linssey Unhrersi ty); his very consi:.lernblc effo'rt 0:-1

I also have plcas'J.re in a~kuowledging 2.ssistancr) from the following:

Prof. B.il. ;'/atkin for ini tiaJ. discussions on the study, and for his encouraeement.

Mr. C.1I.S. van Kraayenoord for helpful initial discussions on the study, and fo:.:- th0 svpply of the pla.nt mafo:dc:.l t'1rouch the Plant J.:atorial Centre, Water and. Soil Divi::;ion, Ei::1istry of Uorks.

Prof. B.I. Har.tan, for e!'cr]y discussions 0n experiPcntal design.

Dr. H • .J.S. Cler:1m:ts, f or mo.ny valuable discut;sior:s on stati3tj~a1 analysi ~ and interpreta ti(Jn, and fo1· initial assistn.nce wi t!i. 8omputC>r onera. tion.

Prof . R.i::. F1.mfod., for pen;:issio:1 to use his gec1eral statistical proe;r<1n anc. for assistance in it's ap p lie;a tion.

Dr ••

r.

'?. Kerr, for discussions C''Jn:::srning

t :w

neasurement cf w-atcr potential~

Hr. f •• C.P. Chu and. Mr. G.S. Edmeades, for interenting a~d wide-rangin6

diEcussions on many c1.spects of the study.

Mrs. J. Hum;;hries, for her e.x:cellent a>1d e.crnrate typing of this thesis.

The Commissioner of Works, 1'!inis try of ~forks, for supporting my

application to the State Services Con.mission through the ::; taff of the Water and Soil Division, Ministry of Wo::ks at Palmerston North and Wellington.

T:10 St.'.::t<? 3orvices Co'.':,:1ic;;ion, f01' fi,,ancio.l su;.1:r,0:-t, ·,;j_thout which ::,is stud.:· would not hnvc boon possible.

Finally, I wish to thank my wife Catherine, for assistance with the

considerable statistical analysis involved, and for unfailing su:in1ort and encouragem0nt; her patience far e:ccecdec oy ovm.

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1.1

The Use of

Fo

r

ulus

3;cciG

3

i~ Ke~ Zcal~n1 1.2 Factorf~ in..f:.uencir2c Vcgotc1ti\tc~ rrcpa~2--t:Lor1 of

i :i.i iii iv

V

1

2

1.

2

.1 .Sbe of

Cu-t:t:i.1,6 ⁴

1.

2

. 2 Physi olo

gic~! ~gc 1. 2. 3 Teu::,er;:;. turc

1 • 2. 4 :Co:.."r::.?.ncy

1.2.5

Eorr.:on"'"l llccliHtion

i n

i}o:nr.o.n~y 1 • 3 1:,r a te r 3 t2. ttJ3

1 •

3.

1 Gcner~.l

1.3.

2 Nate~ Deficits and

Gr o~t t

1.

3. 3

^'f'h^c ^J.~ea^sux·eme^nt

of

'/at,.;r

D eficit s

Cf::'Y'l'ER 'l''JO - EET.r:O:!:JS

2.1 Experimen

t al Obj ectives 2.2 Gener

al Techniques

2.2.1 Growth Conditions

2.2.2 Eeasurement of W ater C

cntent

2. 2.3

Heasuren:ent of ¹

-.ra

tcr T'otcntial

2.2.4

He1.lsurement oZ

Gro

wth Responses 2. 2.

5 Control of

Other

Factors ifli'lu::mcing

Propagation

2.3 Erperime nt~l Procedures

5 6

6

8

10

12

16

19

20

20 21

22

2. 3.1 Study

of Seasonal Cha

nges in 1·la

ter

Sfatu:c? 25

2.3.2 ~he Effect of

light on Budb

r eak an d

Root

Initiation

2. 3.'.3 The E:f;'fect of

Relativ e

Hum

idity on Water Loss

27

28

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G1 .. o:·1·~!1

3.

3

'::he

Bffcic

^t. of V.cht oa r:ro1vth

3.3 . 3

Roct C

~cw

th

3. ~.1 S:!-loo~:

G::.·o-.dJ1

29

3 6

42 ,1.2

47

1i9

3.4 .• 2 Ro0t G:.:owth 1;9

3 . 4. 3

Final D.rT ~foiGht,_;

55

Ini2tion

5G

3

, 5 .1

~later Po'ccntfo.J.:.: ~li thi:1 Cuttinz:s

3.5 .3

Relation beh~cm, '/nter Con:c:'lt anc'~ W:.:.b.H

3. 5

•. 1-

The Incitlence of Shnot and. Root GrO'i·rth 3. 5,

5

Shoot Growth

3.5.6 Root Growth

3.5.7

Relation betwe

en

Inh:rnal ••later Status

and Growth

CHJ..?T~R FOUR - DISCuSSIOH

4

.1 Seo.sonal

C

hanges in Wate:r Status

4.2

The Effect of Relative Humidity OP

~'later Loss 4.3

^The ^Effect

of

Endogenous Auxin

on

Growth

4.4.

The Effect

of i,ight on

Growth

4.5

^T^he^E

ffect

^{of 'i'la}

t

er Stress

on

Bud-break and Hoot In~tiation - A General D~scu3$ion

CEAPTEh FIVS - CONCLUSIONS

L

I

ST OF REFBR~rc:ss

56 60

60 68

82

86 87 92 94

95

99

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Apper,diz

J~p:)0nclix. 2 .P.:,pe:::,c1.:i :{ ^'7...)

1~

: .~r

er: O_j }:

4

}\. ..,·pe1:.di:K

5

Appeu3ix 6 Appe11d2.x 7

.Appcmc1:b:: 8

AJJpcndiz 9 :

StatjGtical .J.n:::Jy~;is of the uffect of Relative J:w:1idi

t:;

on 'la tcr 1.8SS froi:: Cui.tin₆3

St2.ti~~tic2.l I:n(1Jy~·it; of ^+1-,^{L,,.r. ..}^t...^., effect of Light on C)'Oirt}1 A ,,pe:10L,: 10: Stai.:is tica1 A2,.'.'.l:,-·sis of the effect of ExcgcnOllS Am:::i. '1

on

Growth

.

Appendix

11: Stati8tical

An

a

lyaiG

o[

Wat

er Status during

the

experir:ient on the cf.f'ects of ~.'o.ter Strc:0.::: on C-ro,r~}-;

.A:;::,per~c.i:,c 12: St'.:',tistical Ano.J.yr:is 0f .Shoot Grc·,;tL u1,2·:i::1c; the ex:;_)cri1:1.ent on be effe.::ts of WG.ter Stress on G1·0Hth Appendix 13: Stati

s

tic

a

l Analy~Jis of P.oot Growth d.urinE:; be

experir:ie:nt on the effect of ',.'a tcr Stress on Grout}i

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Jntroduction

Within the last century, the vegct,,.tion of now Zealancl hns lmdcrcono a massivu change. A high proportion of th0 steep] 2nds, a:r.d virtually a] l of the flat and rolline cou_'ltry has been co.averted f::i.·01r. ten11-:.:ru.te rain- forest to grassland which has resul focl in considero.bly incrc.~.scd runoff. The inherently unstable natm·e of much of the scdinentar,1 r,arcnt material has not re:sisted this change well, and e rocion b .. s bcr,or,1e a significant probleri in sooe areas.

Te:chniques of soi l conservation and runoff control have been based mainly on plantings of the genus Populus in the fol';:;. of npoles" some 1 () to

12 feet long which can be established in the presence of stocl:, under Farm Plans organised by local catch.ment authori tios. The total nUlllber of poles planted in 1967 was 400,000 - do¹1ble the number of 19G2 - and this i s expected to at least double again. However, in S})ite of advo.nta,~es in propagation, adaptabili ty, growth ra+,e

anu

root sysfom char.1ctcristics, problems in the establishment of poplar and ,-1ill0i-r have arisen. The mo::;t obv::..ous of these is animal damage, chiefly ea ttle ( through rubbinc ai10. bo.rk bi ting) and opossur.l (browsing of foliage). A SlJ'Vey comnissioned by tlw Soil Conserv2.tion o.nd Rivers Control Council in 1968 investie;2.ted the Jovel of pole loss and found a mortality of 24.T~ and 41.t0 over t!1e first o.nd second years respectively (Edwards; 1968, 1969 a). Althcu(;h the r:,_ajor factors could not be posi tivoly identified, i t uas apparcmt th::i. t :,i te factors, and water stress in particular , ~-rare major causes of loi-,s.

'.!.'his study investigated the importance of water reJ.Qtions in t:!-lb vegetative :propa~ation of PoJ.>ulus species. In :!')articular, it was clesi[;nocl

to establish the levels of ua ter stress iv"hich uoulcl. limi t +,he initiation of growth in both root initials and buds.