Experiment 1: Cell Water Potential
Christine Marie H. Ulbis, Adrionna Faye Pauline A. Uy, Gian L. Veloso, Bianca T. Villagoe! "e#artent o$ Biological %ciences College o$ %cience, Uni&ersity o$ %anto Toas 's#a(a, Manila Phili##ines
Abstract
The water potential was measured for each root crops. It resulted to values, -0.7220, -0.7059, -1.0999, -0.8191, -1.218, -1.2271, -1.!"08, -1.!779, -0.""9!, -1.0121 from #roups 1-10, respectivel$. %imilarl$, %imilarl$, the osmotic potential for each root crop was also measured, the values for camote ran#es from -0."57 &'a to !.722 &'a, for potato it ran#es from 0.1!25 &'a to 0."95 &'a, for carrot it ran#es from 1.1002 1.1002 &'a to 1.7801 &'a, &'a, for (icama it ran#es from from 2.07 &'a &'a to !.8!0 &'a and for for )adish it ran#es from 0.29 &'a to 1.0089 &'a..
*e$words+ smotic smotic 'otential, 'otential, ater ater 'otential, 'ressure 'ressure 'otential, ree/in# ree/in# 'oint, )oot )oot rops
Introduction
Cell Cell )ater Potent Potential ial,, sybol syboli!e i!ed d by * +the +the Gree Gree letter letter psi-, psi-, is de$ined as the energy reuired $or /ater to o&e $ro the sa#le and into into a relati relati&ely &ely #ure $ree $ree /ater /ater in re$ere re$erence nce condit condition ions. s. Throu Through gh the #roces #rocesss o$ ososi ososis, s, /ate /aterr o&e o&ess $ro $ro a regi region on o$ high high area area o$ conc concen entr trat atio ion n to a regi region on o$ lo/ lo/ area area o$ concen concentra tratio tion. n. Addit Addition ionally ally,, concen concentra tratio tion, n, #ressure and gra&ity are a0or contributing $actors in a calculating a #lant1s /ater #otential +%inauer, 2345-. Cryosc Cryosco#y o#y is the deter deterina inatio tion n o$ the de#r de#res essi sion on in $ree $ree!i !ing ng #oin #ointt unto unto /hic /hich h olecular /eights o$ the dissol&ed solutes can be deterined. The $ree!ing #oint occurs /hen the te#erature o$ the liuid state o$ a liuid substance is in euilibriu to its solid state. 6t has a colligati&e #ro#erty eaning the $ree!ing #oint lo/ers /hen a co#ound or ore dissol&ed solutes are added. 7nce the $ree!ing #oint is deterined, it can be used to calculate $or $or the the solu solute te #ote #otent ntia iall /hic /hich h is #art #art o$ the the euati euation on in calcul calculati ating ng $or the #lant1 #lant1ss /ater /ater #otential.
This This e8#e e8#eri rient ent ais ais to eas easur uree the the /ater #otential and osotic #otential in a #lant tissue and then calculate the #ressure #otential. Methodology
'ight 'ight di$$e di$$eren rentt sucros sucrosee concen concentra tratio tions ns +dH27, 34., 34., 3.2, 3.2, 3.9, 3.9, 3.:, 3.:, 3.5, 3.5, 3.;, 3.;, 3.< 3.<-- /ere /ere #re# #re#ar ared ed.. <5 <5L o$ each each /ere /ere dis#ensed se#arately into #lastic cu#s. %i8teen cyli cylind nder erss /ere /ere bore bore $ro $ro the the root root cro# cro#ss +di$$erent #lants /ere assigned on each grou#using a =o. 5 cor borer. Cylinders /ere #laced in co&ered #lastic cu#s to #re&ent the $ro drying out. 'ach cylinder /as cut a##ro8iately :c and the reaining #lant sa#les /ere sa&ed $or Part B o$ the e8#erient. The cylinders /ere blotted /ith #a#er to/els and /eighed in sets o$ t/o. t/o. The The /eigh /eights ts /ere /ere record recorded. ed. 7ne set o$ cylinders /as #ut in each o$ the beaers /ith the said sucrose concentration solutions. A$ter 4.5 hours, the cylinders /ere reo&ed, blotted /ith #a#er to/els and /eighed again. The /eights /ere recorded. The change in /eight and the #ercent change in /eight /ere then co#uted. The The resu result ltss /ere /ere tabu tabula late ted d and and the the #erc #ercen entt change in /eight &ersus sucrose concentration /as #lotted /ith the best>$it straight line dra/n through the #oints. The olal concentration o$
sucrose that gi&es 3? change in /eight /as then deterined. The /ater #otential o$ the root cro#s /ere the deterined. The reaining root cro#s $ro Part A o$ the e8#erient /ere #laced in a blender. The tissue /as #ureed. The blended root cro#s /ere $iltered /ith cheesecloth to reo&e cell /all and debris, and /as then co&ered in beaer. ;3L sa# /as #oured in 253L 'rleneyer $las /ith agnetic stirring bar and the theroeter /as inserted. The $las /as surrounded /ith ice>salt bath and /as stirred &igorously. A$ter the te#erature /as 4oC, the te#erature /as recorded e&ery 43 seconds. The data /as recorded and the te#erature &ersus tie gra#h /as constructed. The true $ree!ing #oint and solute #otential /as then deterined. The #ressure #otential o$ the cells o$ the root cro#s /ere then calculated. Based on the co#uted &alues $or Parts A and B, the /ater #otential o$ the root cro#s /ere deterined. The &alues $or all #lant sa#les /ere then co#ared.
Results and Discussion
6n theory, no net gain or loss o$ /ater in tissue a$ter iersion in a solution o$ no/n olarity eans that its /ater #otential is eual to that o$ the e8ternal solution. '#loying the Gra&ietric Techniue, /ater #otential &alues ay be negati&e due to the in$iltration o$ /ater and solutes /ithin the a#o#last +%au#e, 233@-. Bland and Tanner +4@5- re#orted that the osotic #otential $or a #otato tube is in the range o$ >3.5 to >4.59 MPa. The root cro#s should $all /ithin that range. 6n this e8#erient, the sa#les /ere iersed in solution /ith a &ariation o$ sucrose concentration resulting to the losing or gaining o$ /ater by the #rocess o$ ososis. 7sosis is the s#ontaneous net o&eent o$ sol&ent olecules through a sei>#ereable ebrane into a region o$ higher solute concentration +Haynie, 2334-. 6$ the sa#les /ere #laced in a solution o$ higher solute concentration, +hy#ertonic solution- the /ater /ill go out o$ cell, thus the decrease in the /eight o$ the
sa#les. 6n contrast, i$ the sa#les /ere #laced in a solution o$ lo/er solute concentration, +hy#otonic solution- the /ater /ill go inside the cell, thus the increase in the /eight o$ the sa#les. This is because dissol&ed solutes contribute to the osotic #ressure or #otential. %olutes reduce /ater #otential by consuing soe o$ the #otential energy a&ailable in the /ater. According to raer Myers +2342-, osotic #ressure is the e8ternal #ressure reuired to be a##lied so that there is no net o&eent o$ sol&ent across the ebrane +isotonic-. 6t is a colligati&e #ro#erty /hich de#ends u#on the concentration o$ solute olecules or ions, but not u#on the identity o$ the solute. 6n these calculations, olality +- is used /hich is de$ined as the nuber o$ oles dissol&ed #er ilogra o$ sol&ent. This is because the ass o$ sol&ent doesnDt change /ith te#erature unlie the &olue. This is the reason /hy olality is #re$erred o&er olarity +oles #er liter-. 7sotic #ressure and #otential, in turn, a$$ects /ater #otential. )ater #otential is the tendency o$ the /ater to o&e into or /ithin a syste easured as the aount o$ energy #er unit &olue e8#ressed in ega#ascals +MPa-. )ater #otential can be co#uted atheatically asE
Ψ =Ψ s + Ψ p + Ψ m /here
Ψ s
Ψ
is the /ater #otential o$ a cell,
is the solute or osotic #otential,
is the #ressure #otential and
Ψ m
Ψ p
is the atric
#otential. The #ressure #otential +*#- is the e$$ect o$ hydrostatic #ressure on the #otential energy o$ a solution. 6t is de$ined as 3 MPa $or %TP +absolute #ressure o$ 4 at 3.4 MPa-. For a case o$ a #artial &acuu or tension as in trans#iration, the #ressure #otential is 3. For a case o$ turgor #ressure the #ressure #otential /ould be 3.
Group 1
Group 4
f(x) = - 25.89x + 6.45 R² = 0.97 f(x) = - 8.48x + 4.7 R² = 0.42
igure !o" 1
igure !o" %
Group 2
Group 5
f(x) = - 10.71x + 10.68 R² = 0.1
f(x) = - 29.79x + 9.71 R² = 0.96
igure !o" #
igure !o" &
Group 3
Group 6
f(x) = - 12.78x + 6.05 R² = 0.89
igure !o" $
f(x) = - 23.38x + 6.37 R² = 0.98
igure !o" '
Group 7 f(x) = - 16.02x + 4.79 R² = 0.95
igure !o" (
Group 8 f(x) = - 10.55x + 4.93 R² = 0.78
Group 10 f(x) = - 38.37x + 17.39 R² = 0.99
igure !o" 1+
As seen in Figures 4>43, it is constant $or all grou#s that I)? is in&ersely #ro#ortional to sucrose concentration +-. This indicates that as the concentration o$ sucrose increases, the change in the /eight o$ the root cro# decreases. %oe o$ the #lots ha&e lo/ coe$$icient o$ deterination +J 2- +Figures 2:-. 6naccuracies can be caused by i#ro#er blotting, errors in the analytical balanceK lea&ing cylinders in the solutions $or di$$erent aounts o$ tie and e8cessi&e drying out o$ the cylinders.
igure !o" )
Group 9 f(x) = - 24.73x + 14.47 R² = 0.95
The olality /here the #ercent change in /eight +I)?- is eual to 3 re#resents the olality at /hich there is no net o&eent o$ /ater olecules and no osotic gradient, creating an osotic euilibriu. %ince there is no net osotic o&eent, the turgor #ressure, /hich #ushes the #lasa ebrane against the cell /all o$ the #lant sa#le, does not e8ist +%teudle ierann, 234;-. There$ore
Ψ p
3.
,able !o" 1 Water Potentials o- Di--erent Root Crops igure !o" *
As seen in table 4, the cro#s ha&e di$$erent olalities /here I)? 3. The results range $ro 3.2;<; to 3.553@ K /herein caote has the highest and the radish ha&ing the lo/est. The relationshi# o$ solute concentration +in olality- to solute or osotic #otential is gi&en by the &an Dt Ho$$ euation
Ψ s =−miRT /here
m
is the olality +4 olal4 843 9
i is the ioni!ation constant 4
ol9 H27-, $or sucrose, .ol and Joot Cro#s
Potato
Carrot
Nicaa
Caote
Jadish
Molality o$ sucrose /here I)? 3 +-
)ater Potential +MPa-
Gr#. 4
3.2;
>3.<223
Gr#. ;
3.222
>3.<35@
Gr#. 2
3.:9@<
>4.3@@@
Gr#. <
3.92<5
>3.4@4
Gr#. 9
3.:5<
>4.24:
Gr#.
3.:@3;
>4.22<4
Gr#. :
3.5::3
>4.9;3
Gr#. @
3.553@
>4.9<<@
Gr#. 5
3.2;<;
>3.;;@9
Gr#. 43
3.:3:;
>4.3424
Grou#
R
is the gas constant .94N
T is the te#erature in el&in
+2⁰C O2<9-. The negati&ity in osotic #otential is due to the $act that #ure /ater is usually de$ined as ha&ing an osotic #otential +- o$ !ero and the #resence o$ solutes al/ays ae a solution ha&e less /ater than the sae &alue o$ #ure /ater. Thus, the ore solute olecules #resent, the ore negati&e the osotic #otential is. Ty#ical &alues $or cell cyto#las are 3.5 to 4.3 MPa. The resulting solute #otential in N 9 /as con&erted into MPa by di&iding 43 ;. 6t is assued that negligible, thus
Ψ m
is &ery sall and there$ore
, Ψ =Ψ s
.
As seen in table 4, the /ater #otential &aries $ro >3.;;@9 to 4.9<<@ MPaK /herein caote has the highest and the radish ha&ing the lo/est. A ore negati&e /ater #otential indicates that the cells o$ the root cro# contains ore solute. Aong the root cro#s, the cells o$ the caote ha&e the ost solute and the cells o$ the radish ha&e the least solute. %olute #otential is de$ined as the #ressure that ust be a##lied to a solution to #re&ent the in/ard $lo/ o$ /ater through a sei#ereable ebrane. The $lo/ o$ /ater sto#s because the #ressure o$ the solution and the #ressure o$ the /ater are eual. +Martin and Hine, 233-. %olute #otential &alues are al/ays negati&e. The
reason $or the negati&ity o$ solute #otential is due to the $act that #ure /ater, /hich is deterined to contain no solutes, has a solute #otential eui&alent to !ero. By adding solutes, the solution /ould result to ha&e less /ater than the sae &alue o$ #ure /ater. There$ore, it can be said that the ore solute olecules #resent, the ore negati&e the %olute #otential is.
)hereE I$ true $ree!ing #oint I$ D a##arent $ree!ing #oint S degrees o$ su#ercooling +negati&e in sign3.3425 aount o$ /ater +43- that solidi$ies #er degree o$ su#ercooling.
Cryosco#y is a ethod used $or the deterination o$ the lo/ered $ree!ing #oints #roduced in liuid by dissol&ed substances in order to deterine the olecular /eight o$ solutes and &arious #ro#erties o$ solutions. )ith this ethod, the solute #otential o$ e8tracted sa# in #lants can be acuired using the $orulaE
Ψ s =1.10 Δ f c )here in Q4.431 is the ratio o$ the osotic #otential o$ a non>iodi!ed solution +>2.2< MPaand the $ree!ing #oint de#ression o$ sucrose +> 2.3;RC- +%au#e, 233@-,
Δ f ∨T f
is the true
igure 1"1" Depression o- the ree5ing Point o- Potato 67roup 18
$ree!ing #oint and c is the correction $actor or the ratio bet/een the roo te#erature in el&in +2⁰C O2<9- and 2<9 . Furtherore, cryosco#y centers u#on the #henoenon no/n as "e#ression in Free!ing Point. The $ree!ing #oint o$ a substance is the te#erature at /hich a substance1s liuid and solid $or is in euilibriu. This #henoenon dictates that the $ree!ing #oint o$ a #ure sol&ent /ould be higher +less negati&e- than that o$ the $ree!ing #oint o$ a solution. 6t is also a colligati&e #ro#erty /herein it does not de#end on the nature o$ the solute olecules but rather it de#ends only on the aount o$ solute olecules #resent. 6n deterining $ree!ing #oint de#ression on tissue sa#, increase o$ te#erature /ould be a direct result $ro the release o$ the heat o$ $usion /ith sudden increase as the a##arent $ree!ing #oint +I $ D- +%au#e, 233@-. According to Jeiss +4@@;-, a$ter obtaining the correction $or su#er>cooling, the true $ree!ing #oint +I $ - is obtained using the euationE .- / .- 0 +"+1#& 234
igure 1"#" Depression o- the ree5ing Point o- Potato 67roup '8
igure 1"$" Depression o- the ree5ing Point o- Carrot 67roup #8 igure 1"'" Depression o- the ree5ing Point o- 9icama 67roup )8
igure 1"%" Depression o- the ree5ing Point o- Carrot 6group (8 igure 1"(" Depression o- the ree5ing Point o- Camote 67roup %8
igure 1"&" Depression o- the ree5ing Point o- 9icama 67roup $8
igure 1")" Depression o- the ree5ing Point o- Camote 67roup *8
release o$ the heat o$ $usion. Ho/e&er, in $igures, 4.2, 4.:, 4. and 4.@ and the theoretical increase cannot be seen, this ay be because the e8tent o$ the su#ercooling #rocess o$ the root cro# /as not e$$iciently carried out. 6t ay also be because o$ huan error. The e8tent o$ su#er>cooling o$ a solution is the lo/est te#erature &alue obtained. A$ter ra#id increase in te#erature, /hich is a result o$ the heat o$ $usion, the &alue obtained is the a##arent $ree!ing #oint +I $ D- +%au#e, 233@-. Using the euation, I $ I$ D > 3.3425 S, the true $ree!ing #oint $or each o$ the root cro#s /ere obtained. The &alues o$ true $ree!ing #oint $or each root cro# /ere used to calculate their solute #otentials res#ecti&ely. All the obtained results are #resented in Table =o. 2.
igure 1"*" Depression o- the ree5ing Point o- Radish 67roup &8 ,able #" Determination o- ree5ing Point o- Di--erent Root Crops Joot Cro#s
Potato
Carrot
Nicaa
igure 1"1+ Depression o- the ree5ing Point o- Radish 67roup1+8
6n this e8#erient, the conce#t o$ su#ercooling is a##lied. %u#ercooling is de$ined as the #rocess /here in a liuid reaches is $ree!ing #oint but does not crystalli!e. This #rocess occurs because su#ercool liuids are etastable and do not #ossess seeds /hich triggers the crystalli!ation o$ the liuid sa#le. 6n Figures 4.4, 4.9, 4.5, 4.;, 4.< and 4.43, the lo/est #oint in the gra#h corres#onds to the e8tent o$ the su#ercooling #rocess ha##ening /ithin the sa# solution, the abru#t increase $ro the lo/est #oint to its ne8t #oint is tered as the a##arent $ree!ing #ointW. This abru#t increase as sho/n in the stated $igures is because o$ the
Caote
Jadish
Grou#
Gr#. 4
"egree o$ %u#er> cooling >4.:oC
A##arent Free!ing Point +I$ D>4oC
True Free!ing Point +I$ >3.@25oC
%olute Potential +Xs+MPa>4.4@45
Gr#. ;
>3.
>3.
>3.;@49oC
>3.9:
Gr#. 2
>2.:oC
>2oC
>2.9<5oC
>2.
Gr#. <
>4.;oC
>4.:oC
>4.525oC
>4.@4@9
Gr#. 9
>2.
>4oC
>2.;<5oC
>9.25@5
Gr#.
>:.2oC
>2.:oC
>:.4
>5.35<5
Gr#. :
>:oC
>4.2oC
>9.@5oC
>:.99
Gr#. @
>3.;oC
>3.9oC
>3.5@;9oC
>3.<292
Gr#. 5
>4.:oC
>4.9oC
>4.99oC
>4.;<2
Gr#. 43
>4.2oC
>3.@oC
>4.4oC
>4.::45
By obtaining the solute #otential, /e can calculate the #ressure #otential $or each root cro# /ith the $orulaE
Ψ p=Ψ −Ψ s The resulting &alues $or the #ressure #otential is sho/n in Table =o. 9.
,able !o" $ Pressure Potential o- Di--erent Root Crops Joot Cro#s
Grou#
Pressure Potential
Application
Ψ (¿¿ p )
1" Why is the osmotic potential alays negati;e in sign<
¿
Potato Carrot Nicaa Caote Jadish
Gr#. 4 Gr#. ; Gr#. 2 Gr#. < Gr#. 9 Gr#. Gr#. : Gr#. @ Gr#. 5 Gr#. 43
Possible sources o$ error in deterining the true $ree!ing #oint ay be because o$ the state o$ the ice used. There /ere #eriods /ithin the e8#erient /here in other grou#s used elted ice /hile others used ne/ ice.
Potato
Carrot
Nicaa
#" =o do dissol;ed solutes contribute to the ater potential o- the cell<
Grou#
Molality o$ sucrose /here I)? 3 +-
)ater Potential +MPa-
Grou# 4
3.2;
>3.<223
Grou# ;
3.222
>3.<35@
Grou# 2
3.:9@<
>4.3@@@
Grou# <
3.92<5
>3.4@4
Grou# 9
3.:5<
>4.24:
Grou# Caote
Grou# : Grou# @
Jadish
Conclusion
Anser: The &alue o$ osotic #otential is al/ays negati&e in sign since the #resence o$ solutes, /hich /ater binds to through hydrogen bonding consues soe o$ the #otential energy a&ailable in /ater. Thus, it /ill al/ays ae a solution ha&e less /ater than the sae &alue o$ #ure /ater.
3.:;@5 MPa 3.4925 MPa 4.<34 MPa 4.4332 MPa 2.3::< MPa 9.93: MPa 9.:<22 MPa >3.;5:< MPa 4.33@ MPa 3.:2@: MPa Joot Cro#s
MPa, $or Nicaa it ranges $ro 2.3::< MPa to 9.93: MPa and $or Jadish it ranges $ro 3.:2@: MPa to 4.33@ MPa.
Grou# 5 Grou# 43
The /ater #otentials o$ Potato ranges $ro >3.<3 to >3.<2 MPa, Carrot ranges $ro >3.2 to >4.43 MPa, Nicaa ranges $ro >4.24 to >4.29 M#a, Caote ranges >4.9; to >4.9 MPa, and Jadish ranges $ro >3.;< to >4.34 MPa. Caote has the lo/est /ater #otential and highest solute concentrations /hile Jadish has the highest /ater #otential and lo/est solute concentrations. U#on obtaining the /ater #otential and solute #otential, they /ere used to calculate the #ressure #otential $or each o$ the root cro#s. Pressure #otential $or caote ranges $ro >3.;5:< MPa to 9.:<22 MPa, $or #otato it ranges $ro 3.4925 MPa to 3.:;@5 MPa, $or carrot it ranges $ro 4.4332 MPa to 4.<34
Anser: )ater #otential is de$ined by its euationE *
ψ s /here
O ψ p + ψ m , in
ψ s
stands $or the concentration o$ the solutes or the osotic 3.:@3; >4.22<4 #otential and it 3.5::3 >4.9;3 al/ays has a negati&e 3.553@ >4.9<<@ sign because o$ the #resence o$ solutes. 3.2;<; >3.;;@9 %olutes can be 3.:3:; >4.3424 dissol&ed by /ater because /ater can bind through the &ia hydrogen bonding, this #rocess consues soe o$ the #otential energy a&ailable in /ater and since it becoes ore negati&e as ore dissol&ed solutes are added this also lo/ers the /ater #otential o$ the cell.
$" What is the sign o- the pressure potential o- tissues at e>uilibrium< 6?8@ 6+8@ or 68< At incipient plasmolysis< During transpiration< Anser: "uring euilibriu, the sign o$ the #ressure #otential o$ tissues is 3. At inci#ient #lasolysis, the #ressure #otential /ill still be 3
and during transcri#tion, #articularly in 8yle cells, there /ill be a negati&e #ressure #otential.
%" What causes supercooling< Why is the loest temperature reached not considered the -ree5ing point o- the sap solution< Anser: %u#ercooling, also no/n as undercooling, is the #rocess /hen a liuid reaches belo/ its $ree!ing #oint but does not becoe solid. This occurs because su#ercooled liuids that are etastable do not #ossess seeds that ay trigger the crystalli!ation. The reason /hy the lo/est te#erature o$ the sa# solution is not considered because the true $ree!ing #oint $or sa# solutions are calculated using the $orulaE
I$ I$ D > 3.3425 S /herein the lo/est te#erature /hich corres#onds to the degree o$ su#ercooling and the a##arent $ree!ing #oint /hich is the sudden increase in te#erature as /ell as the aount o$ /ater that solidi$ies #er degree o$ su#ercooling are used.
Y9Z '8#eriental '8#lanation o$ %u#ercoolingE )hy /ater does not $ree!e in clouds. +n.d.-. Jetrie&ed 2< February 234< $ro %cience "ailyE htt#sE///.sciencedaily.coreleases23433: 433:2449944:.ht Y:Z Haynie, "onald T. +2334-. iolo#ical Thermod$namics. CabridgeE Cabridge Uni&ersity Press. ##. 49349;. 6%B= 3>524> <@5:@>:. Y5Z Hine, J., Martin, '. +233-. dictionar$ of 3iolo#$ 4"th ed.. 78$ordE 78$ord uni&ersity #ress. Y;Z orner, C. +2342-. lpine Treelines+ unctional 6colo#$ of the lo3al i#h 6levation Tree imits. LondonE%#ringer Basel. Y
&" Do plants ith atery sap ha;e higher or loer ater potential< Explain your anser using actual computed ;alues"
Y@Z 78ley, A., %#ell, '. +2342-. Molar Mass "eterination by "e#ression o$ the Free!ing Point.
Anser: Based on the table #resenting the co#uted &alues $or /ater #otential $or each root cro#s, it can be in$erred that the ore /atery sa# a root cro# has the lo/er its /ater #otential. This is based on the #rinci#le that the higher the concentration o$ solute a root cro# has the ore negati&e its /ater #otential shall be.
Y43Z %au#e, %. +233@-. Measuring )ater Potential by the Gra&ietric Techniue. Plant Physiology. College&ille, M=E College o$ %t. Benedict Jetri&ed 2< February 234< $ro htt#sEe#loyees.csbs0u.edussau#ebiol92<Lab /ater/ater>lab>gra&.ht
(" Re-erences
Y4Z Bland, ). and Tanner, C. +4@5-. Measureent o$ the )ater Potential o$ %tored Potato Tubers. 'lant 'h$siolo#$. (*E @4>@5 Y2Z Cryosco#y +Theory- E Physical Cheistry Virtual Lab E Cheical %ciences E Arita Vish/a Vidya#eetha Virtual Lab. +n.d.-. Jetrie&ed 2< February 234<, $ro htt#E&lab.arita.edu[ sub2brch4@3si99<cnt4
Y44Z %teudle, '., ierann, U. +234;-. '$$ect o$ Turgor Pressure and Cell %i!e on the )all 'lasticity o$ Plant Cells. Plant Physiology, +4<3-. Jetrie&ed March 5, 234;, $ro htt#E///.#lant#hysiol.orgcontent5@22 5.$ull.#d$
