. ~ 
! 
1 '' - ... ~ .. 
• 
,., .... . ,.., .... , 
·~~-: a• , ';\!/' 1 ' '· • t 
. . ( ! 
' ' ' 
J. A. Palto l) 
' · 
'· 
1 t-:m.orucr I o~ 
To under s tand how plarits rcspond to drought s t res~ i t is lWcc s:;a ry to 
know thc r el atj onship hcth'ccn tissuc \.;a t cr contcnt and ti.ssuc "·atL' r pllt ~"n -
tiui and its osmot i c an<.l rugor componC'nts (l':eathcr l cy , 1970 : h' i ebc . 1 ~)72 ) , 
espccially s ince it a llows thc cstim.:1tion of :.o~ aLl<.l i t i on:tl ~o.·atcr r c l:t t ions 
chnractcris tics , such as the ccll wall water ton t cnt anJ its cbst ici t y 
(1'yrce c t al 1973) . 0 1eung and Tyrcc ( 1975) · fmmd out tha t t hc osmot i.c pr cs-
--
. ! 
surc at full t ur gor , ns well as at ind.piént pl asmol i s is , anc! <:~11 \·m t er 
• ..1~ 
cl asticity are all c loscly .r el atcd to the~ p.:>i.nt '"hcre thc lea f m.1y oslooreg\l.~a-
• /• ... ... ,! ~ 
te or cons erve watcr within a definc.-d r ange of changes in the cnvin.1mncnt :Jl 
mcl (1977. ) f OlUld out rcccnt l y t hnt thcse par runctcrs mcy be de t c n ni ned by thc 
El65) . Thj s tcchniqu -:: m:-t y be usoJ in cl abora t i ng prc~sure - volwnc ,-, :! '\'('~ , 
rc l;~ t.í ng thc os1mtic prcs sure.., turgor prcssure and Hat e t· po t C'Ilt i :tl o r \he 
1) 
l'os tgn1dt.::1te RescJ r ch i ntern, Cent ro . lntcmacionul de Agr i cultura 
Trop i ca l , CIAT , .\p:...rt:.illo 1\é rco 67-13 , D .U, Culoutbia . 
¡ \\'t • 
L.:~Wt_:·::-:..:-=-.:..:· -:=:-::-=~·::::=-:~=-:.:..:· -::-=::::~::::::::::::-::.:~::-~:::':":"..:-~~~·~-~~---'!-~,..-..,--.......__!"-"==-·-- ---· -.............. .. -- --
.. 
1 
1 
1 
\, 
·. 
103 
e:.. ~·· • ·~ \ • ,, 
. :. ... 
.. 
lcavcs or branches 1 1-dth the rclative water contcnt . 
Effccts anJ diffcrcncc!3 in response to drought stress in n .. n v.trictJcs 
of c.assava (~lar~hot csc~19nta Crantt) 1 havc bccn sugge~tcd .:u1ci c0rre l:tt cll 
~i th 1 O\.J copaci t)' 1-m t e r r r:!t cntion so:i ls (CIAT 1 Annual Rcport 1 19 7 ~)). 
The ph)'siologic<•l hasis of thcse intra and 1ntc:-vari<.· ta1 d1 f t"e t vrkt' .S 
ncc,l :=; tr.) l>l' c s t :1bl i~;hcd u1 ordcr to cxplain sclection for drou~ht :·<·> t :-. t an · 
ce. Cor.tpJratin: :.;tudics o( tis sur.: ,,·atcr relations of '-'OoJ)' s pt·crc:.; (.J: •r 
vis and J:.tn·.is 1 1%3), [ucal yptus (l.aJigesl 197813) anJ 111 p:.t s turv:, ( 1\ il ~·,,_, n 
et al_, 1 9~9) have pnwjJr:d useíul data. 
~lorc rcccntly 1 attcntlon hJs uccn focusscd on the ccntributi <•Jl t :1:1t 
\o.'atcr c.ontai.J1cd in thc tis~ues may have on t.he response to droughr stress 
élJld thc q:1ar.tification of such reserves as a11 import:tnt pn1·t on the corrcla ~ 
tion of water stress cffccts. 
1\vo cxpcr.ir.lcnts ,,·ere conductcd: 1) To examine the opplication and other 
impl5c...1tions of thc prcssurc/vol"...une t<..'Chniquc in the Sl\ldy of '"::~ter stress 
in cassava pl:lnt. 2) To Jctcnnine thc rclation of thc w:-~tc1 cont.<.'nt in thc 
tissue .:md its .... -ntcr potcntial. 
~tATFJU.\LS A'\l) ~[E1H.lf6 
nr:mchC's o[ C:l % a\' J pl:mt 1 (~taniho.!:_ csculent.~~ Crnnt.:) 1 varil' i Í l' ~ 'i Col 
22 ~u : :.l ~ ~ H":' SS! ,,·c1·c S;tmpleJ from irrigatcc.l plots and :tl!"o from ¡d o! s h"i t :1 
plastic covcn·d thc so'il to prt'vcnt rain cntcdng th~ soi 1 durtn¡: tltt' groh•ing 
pcriC<I. h":tt c r r<·l¡¡t i o l1 '; in thC' ficld anJ lnhorntor)' ,,·<' re c s t j¡¡::tt\."..1 for t•.tch 
v:lricty. 
.. 1 
.._. 
~ 
" 
:1 
¡,> 
1 
1 
i 
1nc prcssurc-voltnnc tcchnictuc \\'as u~cd in tlK• dctcrminat ion of char~c.:t <:-
ristic ~; of .... -~ter rc l oU ons 1 h:l s c<.l on thc use of thc ~ l rcssun.· ch.w;k r (1•/\' J 
of Tyr<:l' anll lbn~:'!C l ( 1972) ; 1')'Tl'C' I Ibint )' ;m<.l ncins ( 1973) . 
Htc trJJKh<.•s \.:ere co11 ec tcd b0t'.-.:ccn 07:30 and 8:30 i n thc mcntlll!;! 1 pb · 
ccJ in h';.J t c r, rC'et:t h·hils t inmerscJ in \,·atcr :.t.nd :t¿:~in hyJr:n cd (t:J r lhn t ur-
Ü\C'l' lmur~ , but SO:llC' branchcs t3kcn to thc lahoratory 1vcrc hyd 1 :lt l'd !·ur 1 S 
and in:>crtcd in the prcssurl~ ch:tmbcr 1 J.caving only a 1 c:m lc: :tr;), t uf t hc pe -
tiole outsirle . Gas pressurc in thc ch~tmbcr ~·as initi:1lly izKrl':Jscd until t lw 
bnbncing prcssu re of the 1~atcr in thc .>...-ylcm 1.:as obta incd. La t e r, i t \\as b-
crcnscd and kcp t at S bars f or 20 minutes. W:.tt<.:r ex.Jd<..'<.l from this c11t .... -as 
easíly coll cc t cd using n vi::tl <:onn!"lect.cd to a glass-tubc (S - G an. long) , anJ 
thc ch~ngcs in thc h'fÜght of thc tubc-bottlc gnvc thc r.JC::ISilrc·mcnt or \\:lter 
exprcssed at that bolanc i.ng prcssurc . This proccdurc wl.ls rcpeatcd sevcr<d t i-
mes aml cach t imc t. he pressun.' lv:IS incrcaseJ él furthc r S bnre~; unt ~ l ¡~r<'ssurcs 
M~.'Jtl')"'t,IIIO:~f"'HI'\~ll>'ii\(~. ( t 
J . , ·' 1 • ' i· \ l .. ~ .. • , 1 .. • • J• 
~ 1 , 
' rcnK>v ing leaf from thc pre!.surc ch•unbt~r . thc fi-
nal frcsh 1\'Cight' of thc lcaf 1\:lS obtaillcd (FhL) . Frc~h ,.eight of the l C':lf 
a ta givcn ba l :mcing prcssurc w:1 s cstinntcd by t hc aJdi.tion o \ thc '-'l'Í~~h t. o f 
CXUc..b tcJ \,'n t cr be 1 0\v t ha t prCSSI\rC 1 1\Í th t he fina J f r e:; h h (' i ¡:h t O f t he !1-:tl· . 
t hC' frl' s h ''~·.i ~:h t o f tht· lc:1f , to obt.1 in thc n•fo rc l ht' t"rC'sh ~> ci 1 .h t t1f t ht· 
lOS 
i 
·~ 
• 
sure (variable values of t otal water potcnti al) \verc calcula t cJ hy t hc fol -
FWL D\\'L 
Rh'C "'-- - ----
1W DI\'L 
Pa ralllC t c r ~. of osmo t i c pot cntial at full turgor (\ll11 1 00 ) , w:Jt c r jl(l t cntléd 
invC'rsc.: pl o t u í t hc bJl:tnc iJ1¡~ r rcs~urc (1 /~;~) aga i ns t tltt' r ('l: ttÍ\'L' h: t'.n L"nn-
te.n liH\'C) , hy tite cxtr:lpo lati on o f the st r:-~i~l.+ linc . Otltc r \':llt ll:'- •11 • . 
and l!•p lú'rc· ca le u la t ed f r om t he H' la ti ons: 
~·n 1 o o 
; \).¡ t ot a l = ,,, + ' ''·· . 
"'P -+ .. Hl\'C 
Thc moJule of thc c l as ticity of lca f tissuc (e) , ' ''élS tlct C!lninrd :JS fol · 
.. .. ....,..~ ·-
t¡¡P = e ( R\~C PJ\'C ) n 
RI\'C0 .. 
'''hcrc n js thc slopc of thc linear rclation bctHccn log . ~·p and thc 
ruvc m,·co 
.., 
HESi li.TS ,'.J\Tl Dl SCUSS l O~ 1 
~ 
1 
;;) App l icat i o:t o f thc pre :-;~ urc/\'o l Luoo t ccllll iquc . 
Almos t :-~ ll t hc p rcssurc vo l tunc curves ha \'C bL'<'I! ,·;; •de i t• ~ t w l tt", of 
1 
~~ 1 
1 ' 
wocxJy s pccics . Thcr usua lly pr('scnt a ccrtain curvi linc.lr follt'l .l'd ¡ , ~ - :1 l i · 
nc3r rc l ut i onship , but i n 10\ f o thc dctcnni nations , dc rl cc t io n::- frot:l tht· l i-
1 
1.-.--~.-... .... ~"'-*.....W•w•••·rw...._,. e ,.OWWMMIHOl'A'WtrDLORCPIMalfCilt .. W'.,.....,.,~,.r,. ·m ;ttn&• ,k,,., ka'hfteti&.ft._~ 
' . 
.. 1 \ 1 
í• 
11 
106 
...... 
,\ .. 
· ... ~- ....... ~··.·, 
.. 
with rclativc contcnts of \vate r 10\ver thari' 60-55\ (Wllson ct o1, 1~)7~1 ) . 
11 111 cass:t\':1 , a ssoci:n ed l>i.th snnll changcs in thc rel:ltive l>:tt<'r e\ ,, ,l·:~t ( !' i:· .. 
il 
........ 
1 
•• 
l'Vcr, thc cffcct on C.í'>S<•V:t ,,·as prcscnt on l )' on s trcsscd lC't\('~ u f li'' ' \·:1ril'· 
•• 
•• 
•• 
vcrc de(TL':l SL' , m:1king thc cfh:ct rnorc outstar:d1n¡', th:lJl thL· Plll' P''L'~;L'Ilt c·:.l cm 
s tr<:sscJ )caves o f ~~ ~lcx 59 ( Fi g. 2-B), \\'ld ch ra: t)' indic:t :. l' a hi¡•.her t.t unhcr 
of dcéid cclls in strcs~:('d l caves o( ~~ Col 22 . 
1· 1 
•• 
Somc unclcar and tmconsist~llt diffcrcnccs ~>'e re ohsc1-vcd among d: tla ¡¡¡¡J 
~)rcliminary cst:iJnations obtaincJ in thc laboratory . Such ui.ffcrcnn's mar on-
ly he assoc.iatcJ with thc lcnght of time of the doy Juring h'hich till' lC'.wes 
!1 
1 
1 p:.1sturr:s dur in¡: hrdr:tt:lt i on ¡wr ioJs s hortcr than 8 ho: trs. 11(1\,c\·cr , 11 js 
•· L' 
1 
., 
jmport ;Htt to considcr thc rffect of lotcx in c;~s~;;t\';t , h'hi c it f'l o~>:; hlll'll tltC' 
h rancl t is cut, duc t o thc pos iti\'C' prC'ssurc en thr \'C'SS l C'~; (E~; t it , 1 ~)7S); 
1 
.. 
' 
1 
1 
.. 
1 .. - 107 - .. ~ .. · ' ... . ', 
.. a .. 
~ 
\a 
1\',\lER I~ELATI0:-1S ON UN-STHESSEil LfA\1:S 
H (OtllL' IH in tk.~ tisst:c and their dcflcctions on LUl-stn'SSL~Ll 1c·¡1vc:; ;11\; ¡•re: · 
6 SC!J1 Lcd on figures 3,\ anJ ~n, for ~~ Col 22 nn:J ~~ ~lex 59 rcs¡;(?ct i ve l y. 
3 
Thc th·o cu r ves prcscnt an inflcction point in the rcgi on o[ n. ú·1 b:1rs- 1 
\o.'hC·J'l: thc lir.<:;¡r p:lrt o( t hc rl' la tior¡ bcgins. B}' thc extr:l¡ ,obti•lll l,f' l~ t i .-.. 11-
J• 
0: 
a :;1 
.! 
'l ~j :u 
-~  L1 ... 
thc cXti·apoi:J:i·.m 0f thC' :!bsciss;t g1vcs thc \•::H•:r fr :1ctiot1 uf tlh· c·: JI " :!11 
i ¡ ~ 1 
l !.·; 1 
.. 
·1 :.:~ . 
\ ~ 
•' fJ ; 
.rl }! 
.. ~ t• 
J 
h~utd, c:;t i.JI':Jll'd V;J!ucs for I>:Jtcr ft'\ICtion 0:1 rhc ccllt:l:tr 11·;!]l ;1:1d ~ h<.' dr:: 
,,·cight rc1ati ons ~.ml turgid v.cight for thc lc:1vcs (D\\'i./DTl.) :1rC' :1ls;) \· cr~' 
similar. 
i~clat.ivc: h:ttcr contt~n::s at incipiC'nt plasr.olisis (O o) h'crc lhc s:mc f(J r 
1 
'(! 
1 
1 
t cnt i J !, cs:. i::~ti i ons in th._· fi.e iJ du no t sho"· l:lrgt' diífen·ncC's :n:u!IJ' t hl' t~ou 
1' 
1 
.. . ·· .; • . : . • .• · . , ,· .... . · . .. .... ... 1.·· .. ....... · ~ ·· .. : .• . : . • ;. , • • . •• _, . > .... ......... ; •• · . ' . ~.,.;:- . , .. .... · .. ··~·:·:··.:·:-:: .. .. . ·¡ .• :.:;; • • • ; / -·~ ·.-. .~ .. ; ·.'·~·~ 
·• ·, · · · . ·~·· t· ···,·¡ .. ~~-· · •· ··· : •· · ~ ., ,., 1 ' . ·• • .-, ., • ;. ' ,• ·: · • · · · · ·· · · .;- ,:: ' ··· ·, ·!• · •., .;¡ ..... · .. ·\ ' ••1 • , . , ... . ~, · ~ · 1 · ~·,, n' ' ! 'J·t ·· ' · r.: , ;,,"o -,'1!~·· ; ·.~ • . 1·' ' • , , , 1 ,6'' ~ ,L .4.''· J ,; .,.·: ·· 1 •. ·: · , •··•· .. ·,,• 1 .•.: , , .·· ' f, ·: ,_.•.: · ! ·) ·'·• ''·· ,' •• ., • . , . 
,, 
1 
1 
1 
} 
1 
i 
1 
. ''l '.1. >' :.·. '108 . ~ l.~t"¡.-•.. , ... 
.. 
potcntial, reflects a gcnot}-pic diffcrcnce. It is expcctcd, . thc0ri<~ll)' , 
that thc ccllular clongation should not pcrsist wldcr water stress cond i l ioPs , 
(Clcland, 1971) on cclls with ·undcr 1.!111 100 , 
I..abo ratory dc t c nnincd val ucs sho,,n en Tablc 1 wc-rc nct tJK('J1 hc·c au ~<' in 
thcil · c:-tir.ta tion, thc prcssurc· vo llunc tcchniquc was s ub::. t .1nt i:ll ly llt(x!i f Jt"'.l 
h'ith t h(~ t b 1c o ( co11 ec tjnr, dJ) nnd thc lcn t;ht of hyJrnti on pcr!od. 
1\'i\TER PHAfl O~~S ON STI~F.SSED LEf\VES 
Curves rclating the balancing prcssure with thc rcl:nivc ,.:a t cr co:H ci:t 
in thc tissue of drought s úesscd lc:avcs in both M Col 22 anJ 1\1 ~lcx 59 , :t r e 
shmm on figures 41\ and 4R rcspectivclr. Thc shapc and trcncl s o [ t h<' cun '<.' s 
~ ,, ~ .., • ~""' ...... '>f 
are s imi lar tu thoc;c shm-n befare on un-~trcsscd lcnves . Os mot i c po t en tt :l1s 
nf thl" cc lt ~ ot full tur gor ;,' 11 1 0 0 , are similar fo.r both s trcs~ed \'anC'ti L'C.. , i n 
a ran.gl" of -1-1. 2 and - ·r4. 6 b:1rs , hut '"er e 3 .9 and 1. 8 b:trs l oHcr t h:ll1 llw csm.>-
1 o e tic putc·nt iJls .. - Tl.c 
va lucs fo r t hL' \\<l t CJ frani~1 1 011 thc "·a ll cc ll. (O v.·a l l ) , for s t rv ·•~· c·<.l k. t\ ' (' ::0. , 
was 0. 0 1. /\t inc i p i C'nt pl n~liol ys i s thc \\':.l l<!r frac tions 011 t h .: l· t: ll lll.l:- ,,•;1! ; 
(ú \,·:11 1) ,,·ere <'qu:ll fo r s t rcs~;ed an<.l w1 -strcsscd l c;l\'es or ~~ l·lex ',, ~' • 1 ' ltuh L'\' f" l" 
t hc i nc ipil'nt pl :tstr.:-> l )•s i s too~ pl ~1 cc nt hi ehc r h';.¡tcr cnn t r·n t ~ i1 1 t h(· h', l l l 
(O o) fo r 1·1 Co l 2 ~. 
osn).)ti c po lent i:1l •;· .. 1r o with i\ lú,~l' r H'llu.:: tion o f r cb tivc h.l t c r rorttl'n t, 
1 
• l 
l 
j 
\ ) 
:\: .... ,. 
j 
j 
1 
1 
1 
1 
1 
1 
1 
1 
.. 
- • • • • # ~ •• • 1 • • .. ·"- ;,. o • • 
;. ·.· -,; : ~t: ~~,,r.· ~'·'(~': .J~¡~· '. ~~~~;.¿/~~~:~~~41+:~. · .
109 
1n¡~ the ¡ : rcl\dn~: pniod. 
Tlw mininttm; utcn·a ~;<.~ of \.;at('r contcnt in thc ccllul:tr t,..·; tl l ( '· 1- .11 ! 1 ! ·,1 !" 
strcsscxl f•l Col 22 !caves corrclatcs wcll with the bli¡_:hr ::nd <.J ougi11 =-- ~·w i 1 i -
vit)' obsern:d in thc lc:wcs durinc thtJ latcr h'Ccks o ! s trc:; s. c ~ ~ír :11t1! C.1rr 
(19úl), su~¡~cs t that l m' v<llltcs of ,,·atl'r contcnt on thc ce1l 1>:ll 1 L" "·. 11 1) 
durin~ a:.! verse condi t i on~; , 'intiL:atc a tllying up of thc h'a11 ami :;uh:; l'( Pi l' l t l 
\\':J t cr ab:.orbt ion from thc n~st available sitc. Ií thc l>ater con U ·1H (JI\ thl' 
ccll \~a1l (O \\'all) \\Orks as a rcgulator of the water 1 oss f ratn 1 l11: p¡·otoplas t 
it m.1r be suggcstcd th:tt thc maxiroum csti.Jrotctl vi!luc of thc s t rc s ~;t'd ll:<•n's 
of ~1 ~ lcx S~l (70~ approx.) fu:1ction in thc samc ,,·ay during drour.hr :; tn·::s . 
Thc lncx of consldcr~blc d i.ffcrcnccs bctl\ccn tlll~ \';J] ucs o r t he re l:tl ion 1 bcth'C{'Il dty "·e i ght <U ttl turgid ,,·eig!Jt íor thc s trcs:-> Nl and w1- s tre s~: (·,\ 1 e;! ve s • , !P'• ) !' "f~,.-f4'-"f• .. ~''ltll f .., ., ;'-l' '" "'~~l ... Mf,..._l'".,...._,~ .., , .!"'i ,..,...._._~.,._ .... , ....... ,. ,.....,.,. _ _..,.. ...., ...... "- ~V'l\..,'C"' T "' - "t ,. , , - • • ... • , · • ·- • • ,, , • .. , • " ,, t. ·, • ' ' •. , • • , -~ • • r · · 
1 ,.. 
1 
í 
i 
. . 
' 1 
~ . 
1 
0f ~~ ~lcx 59 and ~1 Col 22 , · ,Jgges t. that thc amount of l·:a ter in t IH! C<' 11 1·: ; ; 11 s 
is closcly r<'latC'u to thc diffcrcnt propo.rtions ot th(' llt;t C t ümJ lvl:lll(' -., (l a·ni -
c.:clluloscs and pcctic. ~·. ubsutnce:s). rat.hcr t.han thc t.hicLncss of cc' l 1 11·; 1) 1 
(1 ·• 1 1. 1' ('<:; JO.., S) oC .lJ .,. . .. , 1 , • 
Tl··~ diffl'l'l' l\lv•: .;/ 00 -~'p • ~ltoh· s t.lt:H ~1 ~k·x S~l prc~t'Jol lo )h' t•r \ .si ·w :: 
t h :1n ~~Coi 2.~ t111Jc r Jl11 Jlil:ll ,,·;ttcr conJiti o n ::; , " ·ltillt ir h.l;c ,tt c " i l i ):h, r rt ¡·. i,l it :: 
.. 
' ~· .~ .. t 
a• 
1 
. 
1 
1 
~ 
~· 
. ·~ 
1 
1 
1 
1 
1 
1 , 
. ., 
J. 
1 t~~· ' . 
;, 
bility at uighcr ,.;atcr dcficits serms to have ccrtain adnptativc valuc for 
S¡>cCl CS Which grow v.rcll undcr dry COOUitiOnS (CheUng 'et al 1975) , AdJ j t ÍOII~l l 
.¡<' --
1\ -',• • 
cs tim.:ltions conduc t cd 1 S days aftcr the ~ of thc dry pcriod (Fig . s~~ and 
" ,, .. ,, u , r. 
.• .~~~rt..¡ . • 1 1 
Sb) shO\\Cd that thc osrrctic potcntials o"f' the ' cclls at· full turgor r ctunwd 
. ~~ ... t:.i· · 
' · .... ,, ,x; ~~4,~.' t. 
rclativcly fas t to thc lcvcls of un-strcssed lc~vcs, in a rccovcr y rnngc of 
3.3 and 3 . 9 bars for ~1 Mex 59 and ~~Col. 22. • The tcndency of ~! Col 22 t o r cach 
osmotic potcntinls láth lcs s incrcase of the relatíve h'n t cr contcnt suggC's ts 
a bcttc r nbilit)' t o r ccover comparcd t o ~~ ~~x 59 pl<mts . As a contra:>t t o 
thc es t iiruJtrs o f o~:ootic potmtial ~'T1 100 , M ~icx S~ r cachcd }Oh'C' r l evcl s 0f 
thc \\':Jtr r frnct ion i n thc ccll \o.':Jll (O wall) fastcr t han ~~Co l 2l . 
Thc l oy, cs t and s lo\\est decr eascs o f ·"•atcr contcnt i n thc cr11 h·:l) l 1\c· rc 
in~! Col 22 (3 . S ~ ) r athc r th:m ~~ ~k:x 59 (30~), sugccst i ng th:1 t tite l'l'z:ul:Jtor 
cap~ci t y of t hc ce l1 "·all in~~ Col 22 ruy be an i ndicaUvc f~ctor of t ough-
ncss or acc l in:;:,t.!:;~Uon t o drought , ,,·hic:h is duc t0 tlle hi¡~hcr j¡¡crC':hc in 
thc hcnüccllulosc :u1d pectic subst<mccs produc t ion (G:~ff and Can, 10Cd ) . 
1iüs accli.Jrotization factor con·clntes \\·cll with thc l o"' vnl ucs of thc ;¡¡11 1 0 0 
t 
- IJip est~1tcd for ~~ Col 22, during both stress and r ecO\'Cl'Y cycl e 1 which in-
di ca te m.1re ccll \-:all rigid.i ty. 
• 1 ·•¡ 
Thc valucs of thc clas t.ic 1rriclu1e on thc cc11übr-,.;o:.~n '( c.) '~·h i ch h'crc• 
R\\'C - RI\'C0 • • 
obtaincJ for coch lenf by us ing the ~'p "' e(--.;--=- ) equat1on (L:.11hgcs 
R\VC0 
1975), sh0\"cd t h:lt thc \'aluc~ are highcr in ~1 Col 7.2 t hm'. in ~1 ~!ex ~9, ft>t · 
strcsscJ as ,.-cll as fo r un- st )·cs~C'J l covcs . l !rn,·cvL: f 1 thcrc <l r e 1\0 Si gn i f i-
c:.~nt diffC'rL'nrcs bct,,·ccn tlw v:tl ues f or st r cssC'<l and un-s trC's scd l c;,n·f. o f 
111c valucs culcttüitcd during t hc rC'covcry pc r iod d id n0t 
1 
e __ .._ ___ _......,. ____________ ---- ---. ......;..' -.;"1>-~.-- ....  -::::::::::::o:=--.. .. 
1 
.1 
1 
1· 
a 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1· 
1 \\ ' .... 
111 
. ·'· 
... 
for M Col 22. 11\e data indicatcs a highcr intra-vo.rictal vnrj ati on rat!H.: r 
th::U\ a \'<trintion bct\,·ecn thc th·o vnr.ictics , although ~1 Col 22 !.::ave s ll'ndnl 
to~~·arJ s hi¡~hcr e levcls . Thc clastic module of thc ccll \V:J1J 111.'1)' iw :1 1 ir!i ! · 
cd ch~1ractc.:rjst ic in liml tcd intra-v:trictnl studics , due to a v:1ri :1t i'll ' l :v · 
t\,•ccn thc l c.wes or br•lllchcs uscd , Thc precise vaJ uc·s of e ;~nd rt m;¡ y !H.: ;1 í -
fccted by error sourccs such as thc cquilibriwn prcssurc \vlüch coul d onl y be 
rend arow1d + S bars nml the Hh'C pcrccntat~c ,,,hich Jnakcs an CÁac t dct(:nnina-
' 
tion diff icul t. 
' ; . \: . 
,. 
1 
'· 
1 
t 
•ti ~ 
1 
•l 
i 
,· 
REf.ERF..J'iCES ' . 
Clcland, R. 1971. Ccll wall cxtension: ' Aim. Rcv. Plant Physiol. 22: 197- 2:-:2 . 
. :.-- ~· l• ... ..,. ·"'· 
Chcung, Y. N.S., Tyrce, ~t. T. and Dainty .~J ! -,.1 975. Water rclation!, paraJt~ters 
'¡1 ·.\~~~':'·> 
on single le:tvcs obtainC'd in a ' pressure bomb and sorne ecologk:t l jntt·r-
li, Colombia. 
rsau, ~- 1965 . Pl ~utt ;ut:l t.omy 2nd. ed. John WilC'y and Sons. Inc \(",, '' ' rk. 
GadnC'r, 1\' .R. í, Fhlig, C.F. 1965 . Physical asp<·c ts of tlw intv:·r;;:J ~> . Jter l'l'-
latió JL<; of plant lC'.wcs. Pl. Physiol. 44 -70 5. 
crops nr.d ~wruc rcccnt stuJies on thc '"atcr relatioaships of ; rpp1L· tn.·es . 
18th. Intern. llortic. Cong. Tel-Aviv. 45: 187 - 197. 
Ike, l.F., TilUrtcll , G.W. and Stcvenson, K.R. 1978 . Evalu:1tiou or prcssure 
chambcr t ecluüque for rncasurCJOOnt of lcaf water potcnt.lal 1n cass"va 
(M.mihot especies) . Can. J. Bot. 56, 1638-1641. 
. . -~. 
J3rvj ~ , P. G. and .J:lrvis ~1. S. 1963 . ll1c \\'atcr r clation.s of trec, scC'd linf.· 
IV. Sorne a!'p<·c t s of thc tissuc wncr relations :md Jrought r•.'s i ~ t ~li K<.'. 
l'li)'S in l. Pl.m t. 1 (!: 501 -506. 
utdif,l'S , I'.Y . 1~ 7 Cl . Son'M.:! nspccts of tiS!;IJC \.;:lt<'r rclations 11 1 thlL'<.' ¡l(•pt: -
lations of l:u~t.lJ.¡~s \'imin:llis . L.1bill. Ncw Phrtol. 75: s:~ 1>:. 
• 
1 
1 '
1 f.
1 
¡. 
1 
t. 
1 
1 
.. 
cquilibrium water rclations ns mcasurcd b)' thc 
prcssurc-bomb tecl1nlque. Can. y Bot. 51: 1471 . 
Wcotherly , P.E. 1970. Some aspects of water rclatiohs . A<h 1 V~ . 3: 171 -
206. 
campo:,, ~· ,., ¡ 1t:. iolo· 
Van llo\ 'l'll'll hh.). 194-
\ülson, J.R. Fishcr, M ... l. Schulze, E.D. 1979. Comparison bct,vccn Pressure-
Volumc und 1~"-point - Hybrt"'mcter Tcchniqucs for detcrnlinlng th"' "'álcr 
rclations charactcri~tics oí grass nhd legl..lrOO leavcs. Ot-color,ia (Hcrl.) 
41: 77-88 . 
.. -- ·--~ ..... --- ·· · .. --~-~ ........... _... ___ ._.. ___ ..... 11111.~,. .. --... ··----. .... _. _____ ............ _ .. _______ ,_ ...... _......_ ..... _ .. _,,.~ 
LIST Of TAP.U~S 
1 Tahlc 1. ~ \'aluc:. of the osmotic pa tc-ntial (~111 1 00 ) 0f ccll!; :1t or lll'<ll" .ul l 
•1 tuq~or, fracti ('l1 of !he tot<ll wntcr content rc-~iding in thL' \,al] ( ti "'a11) and thc hulk r.lCXlul~s af clasticlty (e) uf strt ·•.·,h! , tll l-
, ...... t• .(_ ........... ,,...~..,., ._ .,.-~.,.. ..... """.,. . ..,... ....... , ......... ,.~ __ t1, ...... ,.. .... .,,.,,~'r"'"',, .... ,~..,. "'.)\ ...._..,. . .. 0"\. ~ 
1 
1 
1 
1 f ' 
1 ,, 
' . 
1" 
1 
J. 
~· -
1 
1 
1 
~ 
1 
•,_ 
~ lt 
1 
');! 
•• 
1 
~ 
r• 
1 
- -
_ _, - -=- 8l . .. ··- ··- .... ------.. ..· . ~ ... ..,..__ ~-.... ........... 
1 
Tablc 1 . \ 'alucs e : osrotic potcntial (~: .. 1 ~ 0 ) of cells at or r.ear full turgo-:-. 
' 
fractic:l of t~.e t otal 
ME< 59 
·· M. COL 2Z 
.. 
, . a:NrROL 
.:,7:-
J.1. COL 22 
~ 
· .. •atcr ccntc:1t rcsidb~ Íil ti1e "'all (.e lo.-:111) ·and tl-.c bulle nx:x!ul~ clasticity (r. ) of stresscd , 
1 
un-strcsscJ a:nd str~sseJ-rccovcr lcaves of cassav"<l. 
~11 1 0 0 e wall e o Wp · ~ .t.otal D\1./T;:t. ~C\ l);"T 10 0 -w c. 1 
Lab. - 9.3 . .53 ·~ .iO .-13.1 -- -22.4 .28 ~ 3.8 
Field 
R---c.ov. 
L;:b . 
Fíeld. 
Recov . 
L3b. 
Field 
Rccov . 
Uib. 
Ficld 
Pc-:ov. 
-10.7 • 65 
. i l. 2 .36 
-1 0.7 -· • 52 
-14.6 .1 • 70 
-11.3 -~.=! .41 
.¿~ ........ 
-10. 8 .80 
-1 2. 4 .64 
- iO. 2 .66 
- 9.7 - .35 
-14.2 . . • 65 
-10.3 .61 
.82 > ·12.9 --- ·-23.6 .30 
66 .1:[ 16 9 . . 28 ·, " 22 
• J. .• .-• . 4 . ·_ . -: -,.., ·. -i b 
· ~- :6o· . -17 :·{ , ~.::_ ~28.5~ ~:~:~s 
~._.~~ - - -~- ·.·-· .• .. :.~";.< 7 ~ ~sz ~- -~ 11 .s ·=:. .. ~3Z.4 1. ~ : 31 ·• "/ 
•. ·!.;- .7o -- -16.1 -:~ '.-27.4 ,_.· . • 22 
.88 - -:.. 12. z - ' -23.0 ;~ ..• 26 
.82 -15.0 -27.4 .27 
.80 -12.8 -23.0 .27 
.65 . ·14.9 ·24. 6 .26 
.85 -16.7 -30.9 • 28 
.79 .-13. 1 -23.4 .71 
l JIS 
t 3.6 
1 
.3 
• ~r6.0 
'176.0 
p s.o 
~ 
]50.4 
~ 
j78.0 
J 
'fCI.O 
1 
2.2 
5.7 
7.0 
3.2 
4.8 
1.4 
2.6 
2.5 
S.2 
2.5 
2.7 
2. OH 'X 103 
'f 1.98 X 10J 
2.88 X 103 
1.94 X 103 
4.06 X 103 
2. 06 X 103 
-r ~.89 X 10~ 
1. 99 X 103 
'1 
. ·1 . 
¡ { 
. ,i 
~ 
--
"" 
. . 
¡ 
'1 
-< 
1 
1 
. ' ~ 
1 .. 
1 
1 
~ .' !· 
r .1,. 
1 
l& 
•' 
1 
,l 
1 
. ' 
. ¡ 
' 1 .·:) .. : .. ' 
iliazw a e 
Ll!:>l ' OF FIQ.flU:...<.; 
l leriv~tti on of ph)'~ ic:ll ¡xtrarnctcrs from thc r c l:lt ion hf't" ~t· rt rvJ ;¡ -
t i \'C \<."Jte r cuntent in pc rccnt (Ri·,'C) and the r cc ipro~:d u ! ! u t:d 
Fi!;. 2A Dcgcncration of the linear phase as obscncJ in sorne s t r e..;s c·d ll':J· 
2B ves of (A) ~1. !-!EX 59 unu (B) ~l. mL 22 . 
Fig. 3A- Relation bct.,...ecn inverso balancing pressure and tissue n .: 1:tti\c 
., 
. 
3B \o.'3 ter content for lea ves oí .CJ\) . l-J COL 22 and (B) ~1 t·ll:>.: 59. 
'/~-~~L'· -. ·. ,l,~,:Y~-'-"' •. 
Fig . 4A - Rclation bebvcen invcrsc balancing prcssurc a.nd tis sue r cl:..tti\'c ha-
4B - t er contcnt for s trcsscd cassava lcaves of (A) M COL 22 .tnd (B) 
~~ ~w..x 59. 
F.ig . SA Rclation bct\,·ccn invcrsc b:ll:mcing pressure and ti ssuc- r c l Jtiv<.' h'J -
513 - ter con t cn t for s trcsscd -rccovery .cassava lcaves of (/\) .t-1 l.OL 22 
and (B) ~1 MEX 59. 
t 
~·--~· mea a 
. :'!1-. 
iCE j U )4 
• o ... - • ....._.~·--·--
,., 
' : '~ .( ~- ... . 
. ,.,,.~.· . 
. . '· '~~ t :5...:: .. 
. . 
117 
-~ 
0.20 ~ 
~ 20. 
:;) 
.. 
.. 
e 15. 
o. 
0.18 Cll 10. e 
V 
e 5 o 
Freih Weioht of leaf (g) 
0.12 
0.10 1 
1 • 
.. . .• 
0.06 
•' 
0.().4 
• .. 
.... 
"" 
0.02 ··• 
•.... 
'' ~~' .· .... :l 
~~~ iW>M;!;l~.,. .. -.. . ~'~, ~. " 
J ' ' .. ~ Wo ll 
·~ 
'· 
... 
o 
·--'-----'-·----"-·_::" ·--· L ----l ·----· • -----' -
50. 40. ' 30. 70 . 10. o 
------L------Á----~-
100 . 90. 80. 60. 
Rc lotive Wcter Contenl % 
fiG. 1 
Derivoción de los puróme lros f:sir;os Je lo roloción contcn:do relativo de oyvo (CR,\ ) 
recíproco clt>l potencia l du ogua !()tal {1/t.J') y potencio! ,,"presión (1)Jp) c11 yvt.,l. 
( 
J 
~ 
.._ ~ ·- - -~-- - ... rm - ..- ... ...-._ - .... .. . ~ . ..,. ... .......... ...... 
1 ~.\ .Y. ex 5~ 0.20 • 
i 
0.18 ~ 
1 
0.16~ 
\:~ 0.14 
! 
e 0.12 
~ 
... 
~ 
0.. 0.10 
011 
.-::: 
~ o. 
o 
:& 
e 
::: 
~ 
e 
0.04 
0.02 
o 
A' J 
100 90 BO 
FIGS. 2A. - 2B . 
por seq..:ío. 
~ _ .. 
. . 
~ 
_ .. 
... 
..,_ . 
~--
~ 
-- . 
-.< 
~ 
!' 
~..,- ... 
~-.. 
50 
. ' 
. . 
. . 
.~ 
•• .... 4 
40 30 
-1 
e 
u 
C) 
~ 
~ 
.. 
~ 
a.. 
~ 
't• U 
··C 
20 
o 
~ 
CJ 
e 
c:J 
> 
0.04 
0.02 
o 
10 
\ 
• 1 
l 
1 
1 
,"-.,\Col 22 
S) 
-~< -• 
. -~ ... :· 
:-· ~ .. ~ 
-... ~ ;~-~~· ~ 
--- .... ·-··;.". ~- .. · .. -~~~ .. 
;.-:-: :.:...?··:~ 
.... ·~~ -~- .. 
~ -~.- .J '-.:_.;·~~-~> ..... 
.. 
... 
~ 
iOO 90 80 60 50 40 
Relotive water conte-nt % 
30 20 
Mroción de la porci6n lineo! de lo curve de presión/volúmen t:n hojos do dos variedades en streu 
·. 
<lL 
10 
• 
o 
1 .. 
0.2 
0 . 1! 
0.04 
0.02 
o 
r ~ M. Col 22 
100. 90. 80. 
FJG . JA . 
~ 
,$., 20 . 
~ 
:> 
., 
.. 
~ 
a. 
2• 
'ü 
e 
o 
:g 
. 
. 
. 
. 
15 . 
10 . 
5. 
o. 
70. 
11 9 
, .. 
.,. : • .. 1 : 
,·~'t· 
~0 . 
. 
'· 
50 . 
Rel o ti ve Wate r Content % 
' . 
. .' . ~~~~· 
' ... tw 
IN TCP 
~Pn 1 ao 
40. 
0.080 
-12.4 
30 . 
~· ·~·r ' ···'!;-• ~ \ .. ¡ 
t 
• 
__ _.._____ - -
20. 10. 
RctociAn de lo presión d~ balance y conte n ido rela tivo de "'ogu.l e ., e l tc.-jido de ho¡os du yuca, 
variedad M Col 12 o regímenes normal e l de O!lUO . 
.. 
,·_e~ 
.. 
0.20 
0. 18 
o 
: .r ~~z. 
M. MEX 59 
25 
e-
.R 
....... 
20 
e¡ 
... 
:J 
~ 15 
~ 
u. 
01 
e 
V 
e 
o 
:& 
''i·. 
• ~ 4 ., J'¡ 
... 
'" ....... 
' 
' 
... , ! 
' 
120 
. ·~ 
•. 
. .. 
\ 
' .~· 
,. ' 
. "· .. 
. -;.· 
.a ··- 1 
INTCP 
.,_ lhiOO 
. : 
:.y 
' .. 
0.0?2 
- 10.7 
~---..l-- --l---1----'-;-,-~-----'-----1------' 
lOO 90 80 i' o '' 60 50 ~o 
' 
' 
R(llotive Water Co nl"nt % 
30 
(g) 
¡__ _ _ __ 1__.... 
20 10 
FIG . 38. Relación ue lo presión de bolonce y contenido relativo de ogvo e n e l tej ioo de los 
hojas da yuca, variedad M Mcx 59 a regímenes norrnoles de ogua. 
\ 
j' 
'¡¡ 
i 
·~ 
"~l 
., 
o ... Q 
t 
'. 
e 
.& 
...._, 
!! 
::> 
.. 
... 
f 
o. 
01 
.S 
.. , 
V 
3 
:S 
~ 
! 
4) 
> 
e 
1 
il 
"' 1 ' ' ' 
' i 100 90 ' ' 80 70 
FIC. 4A. 
·~ ,. 
_,:. 
. 
. /~' ...... ~t.;: . .' 
Woll 
' 
' 
" ~ .. .:.. ·~,} ~ '· 1 
• ...... ·1·¡ 
:;. ~· 1 
1 .. ~ • 
··::. .. 
60 50 
121 
!urgid 
' weight ... 
... 
1. 9 ' 2.1 ' ... ¡.. 3 
Weight of Leaf (g) 
INT = 
~11 100 
0.070 
-1¿.2 
2.5 
__ _. _____ ..__ - _ ____ l,___....j __ _ 
40 30 20 10 
Relotiv• Water Contont % 
· ~ 
•o! 
! 
f 
. 
. • 
·j 
: 
0.20 
0.18 
0.16 
0.14 
. .,.,,.,., . 
---1 ~ 0.12 
o 
e 
~ 
:;) 
... 
.. 
t! O. lO 
~ 
Ól 
.~ 
V 
e 
o 
~0.08 
• . e 
• > 
e 
o 
.. 
' 
' 
' 
' 
' 
1 ' ' 
Fre~ weight oF leof (9) 
lt:-IKP 0.0681 
~11 1 o e -14.6 
1 ' ·---------~~-----L------~--------~--------"~------~----
100 90 80 70', 60 50 30 
Rela tiva 'Nater Content % 
2.6 2.8 
20 
fiG. 48 . Relación de presión de balance y conten ido relat ivo dt! aguo en el t~jido de hojas 
de M Mex 59. stressados por $equía. 
~. ' 
10 
·:~ 
.1 
.-
.... 
M Col 22 
123 
0.20 
0.18 
0.\h 
0 . 14 
·~ o. 12 ! 
e 
:;) 
::; 
1) 
.... 
o. 10 
n.. 
g' 
u 
e 
o 
lb O.OP. 
~ 
o 
> 
.: 0.06 
... ·o.o-4 
o 
~ 
~ 
'ª-
~ 
5 
.. 
... 
~ 
0.. 
01 
e 
V 
e 
o 
:g 
\ 
20 
15 
\0 
5 
o 
1.7 
' 
' 
' 
' 
~ 
~ 
1.9 
t 
. ' 
2.1 
... 
. 
-L-.. 
2.3 . 
' 
o .0961 :: 
-10.39 
' 
2 .~ 2.7 
... 
' T~ 
, Woll 
--J.----·..L-
- --'-
30. 20 . 10. 
Relotive Water Ce -~ tent 'Yo 
FIG . 5A. 
Relac ión de pre$ÍÓn de bolonce y c.ont.-.nido relat ivo de O!}UO en te¡iuas de ho jas 1e M Col 22, 
dos s.emono1 de~pvé$ de terminone el c.icla de stre!s. 
. . 
.. . 
. 
~ 
~ 
. 
'" 
1 q 
1 
. 
.. 
0.02 
o 
lOO. 90. 
FIG. 5B 
' 
' 
' 
' 
' 
' . ' 
Wall 
1 ' 
_J._ --.J·-----L--·---..L.--~-'---
80. 70. 60. 50. 4Q. 
R~lativo Water Content% 
• ____ _ _;. ___ _ _ J_ 
30. 20. 10. 
Re loc ión d~ presión Je bol once y wntenido re lativo ck agua en tc¡ idlls de ho¡o~ de M Mex 59, 
dos semanas después de te rminarse el ciclo de streu.